fix-vm: use Machine trait exclusively

Cargo.toml

@@ -1,40 +1,43 @@
 [workspace]
 resolver = "3"
 members = [
-    "fix",
-    "fix-bytecode",
-    "fix-compiler",
-    "fix-error",
-    "fix-lang",
-    "fix-runtime",
-    "fix-vm",
+  "fix",
+  "fix-bytecode",
+  "fix-compiler",
+  "fix-error",
+  "fix-lang",
+  "fix-runtime",
+  "fix-vm",
 ]
 
-[profile.profiling]
-inherits = "release"
-debug = true
-
-[profile.lto]
-inherits = "release"
-lto = true
-
 [workspace.dependencies]
-bumpalo = { version = "3.20", features = [
+bumpalo = {
+  version = "3.20",
+  features = [
     "allocator-api2",
     "boxed",
     "collections",
-] }
+  ]
+}
+ere = "0.2"
 ghost-cell = "0.2"
 hashbrown = "0.16"
+likely_stable = "0.1"
 num_enum = "0.7.5"
-smallvec = { version = "1.15", features = ["const_new", "const_generics"] }
-ere = "0.2"
-string-interner = "0.19"
 rnix = "0.14"
 rowan = "0.16"
-likely_stable = "0.1"
+smallvec = { version = "1.15", features = ["const_generics", "const_new"] }
+string-interner = "0.19"
 
 [workspace.dependencies.gc-arena]
 git = "https://github.com/kyren/gc-arena"
 rev = "75671ae03f53718357b741ed4027560f14e90836"
 features = ["allocator-api2", "hashbrown", "smallvec"]
+
+[profile.lto]
+inherits = "release"
+lto = true
+
+[profile.profiling]
+inherits = "release"
+debug = true

fix-compiler/Cargo.toml

@@ -5,13 +5,13 @@ edition = "2024"
 
 [dependencies]
 bumpalo = { workspace = true }
+colored = "3.1.1"
 ghost-cell = { workspace = true }
 hashbrown = { workspace = true }
 num_enum = { workspace = true }
 rnix = { workspace = true }
 rowan = { workspace = true }
 string-interner = { workspace = true }
-colored = "3.1.1"
 
 fix-bytecode = { path = "../fix-bytecode" }
 fix-error = { path = "../fix-error" }

fix-error/Cargo.toml

@@ -5,5 +5,5 @@ edition = "2024"
 
 [dependencies]
 miette = { version = "7.6", features = ["fancy"] }
-thiserror = "2.0"
 rnix = { workspace = true }
+thiserror = "2.0"

fix-lang/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+ere = { workspace = true }
 gc-arena = { workspace = true }
 num_enum = { workspace = true }
 string-interner = { workspace = true }
-ere = { workspace = true }

fix-runtime/Cargo.toml

@@ -6,12 +6,12 @@ edition = "2024"
 [dependencies]
 gc-arena = { workspace = true }
 hashbrown = { workspace = true }
+likely_stable = { workspace = true }
 num_enum = { workspace = true }
 smallvec = { workspace = true }
-string-interner = { workspace = true }
-likely_stable = { workspace = true }
 sptr = "0.3"
+string-interner = { workspace = true }
 
 fix-bytecode = { path = "../fix-bytecode" }
-fix-lang = { path = "../fix-lang" }
 fix-error = { path = "../fix-error" }
+fix-lang = { path = "../fix-lang" }

fix-runtime/src/machine.rs

@@ -26,11 +26,15 @@ use crate::{
 /// - Imports and scope slots (`import_cache_*` / `scope_slot*` / `set_pending_load`)
 pub trait Machine<'gc> {
     fn push(&mut self, val: Value<'gc>);
+    #[must_use]
     fn pop(&mut self) -> Value<'gc>;
+    #[must_use]
     fn peek(&self, depth: usize) -> Value<'gc>;
+    #[must_use]
     fn peek_forced(&self, depth: usize) -> StrictValue<'gc>;
     fn pop_forced(&mut self) -> StrictValue<'gc>;
     fn replace(&mut self, depth: usize, val: Value<'gc>);
+    fn drop_n(&mut self, depth: usize);
     fn stack_len(&self) -> usize;
 
     fn force_slot_to_pc(

fix-vm/Cargo.toml

@@ -3,20 +3,20 @@ name = "fix-vm"
 version = "0.1.0"
 edition = "2024"
 
-[features]
-tailcall = []
-
 [dependencies]
 gc-arena = { workspace = true }
 hashbrown = { workspace = true }
+likely_stable = { workspace = true }
 num_enum = { workspace = true }
 smallvec = { workspace = true }
-string-interner = { workspace = true }
-likely_stable = { workspace = true }
 sptr = "0.3"
+string-interner = { workspace = true }
 sysinfo = { version = "0.38", default-features = false, features = ["system"] }
 
 fix-bytecode = { path = "../fix-bytecode" }
 fix-error = { path = "../fix-error" }
 fix-lang = { path = "../fix-lang" }
 fix-runtime = { path = "../fix-runtime" }
+
+[features]
+tailcall = []

fix-vm/src/dispatch_tailcall.rs

@@ -61,7 +61,7 @@ macro_rules! tail_fn {
             pc: u32,
             fuel: u32,
         ) -> TailResult {
-            let result = vm.$name();
+            let result = crate::instructions::$name(vm);
             tail_dispatch_after!(result, pc + 1, vm, mc, ctx, bc, table, fuel)
         }
     };
@@ -76,7 +76,7 @@ macro_rules! tail_fn {
             fuel: u32,
         ) -> TailResult {
             let mut reader = BytecodeReader::from_after_op(bc, pc as usize);
-            let result = vm.$name(&mut reader);
+            let result = crate::instructions::$name(vm, &mut reader);
             tail_dispatch_after!(result, reader.pc() as u32, vm, mc, ctx, bc, table, fuel)
         }
     };
@@ -91,7 +91,7 @@ macro_rules! tail_fn {
             fuel: u32,
         ) -> TailResult {
             let mut reader = BytecodeReader::from_after_op(bc, pc as usize);
-            let result = vm.$name(&mut reader, mc);
+            let result = crate::instructions::$name(vm, &mut reader, mc);
             tail_dispatch_after!(result, reader.pc() as u32, vm, mc, ctx, bc, table, fuel)
         }
     };
@@ -106,7 +106,7 @@ macro_rules! tail_fn {
             fuel: u32,
         ) -> TailResult {
             let mut reader = BytecodeReader::from_after_op(bc, pc as usize);
-            let result = vm.$name(ctx, &mut reader, mc);
+            let result = crate::instructions::$name(vm, ctx, &mut reader, mc);
             tail_dispatch_after!(result, reader.pc() as u32, vm, mc, ctx, bc, table, fuel)
         }
     };
@@ -120,7 +120,7 @@ macro_rules! tail_fn {
             pc: u32,
             fuel: u32,
         ) -> TailResult {
-            let result = vm.$name(ctx);
+            let result = crate::instructions::$name(vm, ctx);
             tail_dispatch_after!(result, pc + 1, vm, mc, ctx, bc, table, fuel)
         }
     };

fix-vm/src/instructions/arithmetic.rs

@@ -5,267 +5,285 @@ use gc_arena::{Gc, Mutation, RefLock};
 
 use crate::{BytecodeReader, NixNum, Step, VmError, VmRuntimeCtx};
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn op_add(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let (lhs, rhs) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
-        // if the LHS is a path, the result is a path obtained by
-        // canonicalizing the concatenated string. RHS may be a path or a
-        // string. (A `string + path` keeps the string-typed result, handled
-        // by the next branch.)
-        if lhs.is::<Path>() {
-            let (Some(ls), Some(rs)) = (ctx.get_string_or_path(lhs), ctx.get_string_or_path(rhs))
-            else {
-                return self.finish_err(fix_error::Error::eval_error(format!(
-                    "cannot append {} to a path",
-                    rhs.ty()
-                )));
-            };
-            let combined = format!("{ls}{rs}");
-            let canon = canon_path_str(&combined);
-            let sid = ctx.intern_string(canon);
-            self.push(Value::new_inline(fix_runtime::Path(sid)));
-            return Step::Continue(());
-        }
-        if let (Some(ls), Some(rs)) = (ctx.get_string(lhs), ctx.get_string_or_path(rhs)) {
-            let merged = ctx
-                .get_string_context(lhs)
-                .merge(ctx.get_string_context(rhs));
-            let ns = Gc::new(
-                mc,
-                crate::NixString::with_context(format!("{ls}{rs}"), merged),
-            );
-            self.push(Value::new_gc(ns));
-            return Step::Continue(());
-        }
-        let res = numeric_binop(lhs, rhs, mc, i64::wrapping_add, |a, b| a + b);
-        match res {
-            Ok(val) => {
-                self.push(val);
-                Step::Continue(())
-            }
-            Err(e) => self.finish_vm_err(e),
-        }
+#[inline(always)]
+pub(crate) fn op_add<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let (lhs, rhs) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+    // if the LHS is a path, the result is a path obtained by
+    // canonicalizing the concatenated string. RHS may be a path or a
+    // string. (A `string + path` keeps the string-typed result, handled
+    // by the next branch.)
+    if lhs.is::<Path>() {
+        let (Some(ls), Some(rs)) = (ctx.get_string_or_path(lhs), ctx.get_string_or_path(rhs))
+        else {
+            return m.finish_err(fix_error::Error::eval_error(format!(
+                "cannot append {} to a path",
+                rhs.ty()
+            )));
+        };
+        let combined = format!("{ls}{rs}");
+        let canon = canon_path_str(&combined);
+        let sid = ctx.intern_string(canon);
+        m.push(Value::new_inline(fix_runtime::Path(sid)));
+        return Step::Continue(());
     }
-
-    #[inline(always)]
-    pub(crate) fn op_sub(&mut self, reader: &mut BytecodeReader<'_>, mc: &Mutation<'gc>) -> Step {
-        self.op_arith(reader, mc, i64::wrapping_sub, |a, b| a - b)
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_mul(&mut self, reader: &mut BytecodeReader<'_>, mc: &Mutation<'gc>) -> Step {
-        self.op_arith(reader, mc, i64::wrapping_mul, |a, b| a * b)
-    }
-
-    #[inline(always)]
-    fn op_arith(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-        int_op: fn(i64, i64) -> i64,
-        float_op: fn(f64, f64) -> f64,
-    ) -> Step {
-        let (lhs, rhs) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
-        let res = numeric_binop(lhs, rhs, mc, int_op, float_op);
-        match res {
-            Ok(val) => {
-                self.push(val);
-                Step::Continue(())
-            }
-            Err(e) => self.finish_vm_err(e),
-        }
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_div(&mut self, reader: &mut BytecodeReader<'_>, mc: &Mutation<'gc>) -> Step {
-        let (lhs, rhs) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
-        match (get_num(lhs), get_num(rhs)) {
-            (_, Some(NixNum::Int(0))) | (_, Some(NixNum::Float(0.))) => {
-                return self.finish_vm_err(VmError::Uncatchable(fix_error::Error::eval_error(
-                    "division by zero",
-                )));
-            }
-            _ => {}
-        }
-        let res = numeric_binop(lhs, rhs, mc, |a, b| a / b, |a, b| a / b);
-        match res {
-            Ok(val) => {
-                self.push(val);
-                Step::Continue(())
-            }
-            Err(e) => self.finish_vm_err(e),
-        }
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_eq(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let (lhs, rhs) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
-        crate::primops::start_eq(self, ctx, reader, mc, lhs, rhs, false)
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_neq(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let (lhs, rhs) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
-        crate::primops::start_eq(self, ctx, reader, mc, lhs, rhs, true)
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_lt(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        self.compare_values(ctx, reader, mc, Ordering::is_lt)
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_gt(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        self.compare_values(ctx, reader, mc, Ordering::is_gt)
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_leq(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        self.compare_values(ctx, reader, mc, Ordering::is_le)
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_geq(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        self.compare_values(ctx, reader, mc, Ordering::is_ge)
-    }
-
-    fn compare_values(
-        &mut self,
-        ctx: &impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-        pred: fn(Ordering) -> bool,
-    ) -> Step {
-        let (lhs, rhs) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
-        match self.compare_values_inner(ctx, pred, lhs, rhs) {
-            Ok(()) => Step::Continue(()),
-            Err(e) => self.finish_vm_err(e),
-        }
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_concat(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let (l, r) = self.force_and_retry::<(Gc<List>, Gc<List>)>(reader, mc)?;
-        let mut items = smallvec::SmallVec::new();
-        items.extend_from_slice(&l.inner.borrow());
-        items.extend_from_slice(&r.inner.borrow());
-        self.push(Value::new_gc(Gc::new(
+    if let (Some(ls), Some(rs)) = (ctx.get_string(lhs), ctx.get_string_or_path(rhs)) {
+        let merged = ctx
+            .get_string_context(lhs)
+            .merge(ctx.get_string_context(rhs));
+        let ns = Gc::new(
             mc,
-            crate::List {
-                inner: RefLock::new(items),
-            },
-        )));
-        Step::Continue(())
+            crate::NixString::with_context(format!("{ls}{rs}"), merged),
+        );
+        m.push(Value::new_gc(ns));
+        return Step::Continue(());
     }
-
-    #[inline(always)]
-    pub(crate) fn op_update(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let (l, r) = self.force_and_retry::<(Gc<AttrSet>, Gc<AttrSet>)>(reader, mc)?;
-        self.push(Value::new_gc(l.merge(&r, mc)));
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_neg(&mut self, reader: &mut BytecodeReader<'_>, mc: &Mutation<'gc>) -> Step {
-        let rhs = self.force_and_retry::<NixNum>(reader, mc)?;
-        match rhs {
-            NixNum::Int(int) => self.push(Value::make_int(-int, mc)),
-            NixNum::Float(float) => self.push(Value::new_float(-float)),
+    let res = numeric_binop(lhs, rhs, mc, i64::wrapping_add, |a, b| a + b);
+    match res {
+        Ok(val) => {
+            m.push(val);
+            Step::Continue(())
         }
-        Step::Continue(())
+        Err(e) => m.finish_vm_err(e),
     }
+}
 
-    #[inline(always)]
-    pub(crate) fn op_not(&mut self, reader: &mut BytecodeReader<'_>, mc: &Mutation<'gc>) -> Step {
-        let rhs = self.force_and_retry::<bool>(reader, mc)?;
-        self.push(Value::new_inline(!rhs));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_sub<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    op_arith(m, reader, mc, i64::wrapping_sub, |a, b| a - b)
+}
 
-    fn compare_values_inner(
-        &mut self,
-        ctx: &impl VmRuntimeCtx,
-        pred: fn(Ordering) -> bool,
-        lhs: StrictValue<'gc>,
-        rhs: StrictValue<'gc>,
-    ) -> crate::VmResult<()> {
-        if let (Some(a), Some(b)) = (get_num(lhs), get_num(rhs)) {
-            let ord = match (a, b) {
-                (NixNum::Int(a), NixNum::Int(b)) => a.cmp(&b),
-                (NixNum::Float(a), NixNum::Float(b)) => a.partial_cmp(&b).unwrap_or(Ordering::Less),
-                (NixNum::Int(a), NixNum::Float(b)) => {
-                    (a as f64).partial_cmp(&b).unwrap_or(Ordering::Less)
-                }
-                (NixNum::Float(a), NixNum::Int(b)) => {
-                    a.partial_cmp(&(b as f64)).unwrap_or(Ordering::Less)
-                }
-            };
-            self.push(Value::new_inline(pred(ord)));
-            return Ok(());
+#[inline(always)]
+pub(crate) fn op_mul<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    op_arith(m, reader, mc, i64::wrapping_mul, |a, b| a * b)
+}
+
+#[inline(always)]
+fn op_arith<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+    int_op: fn(i64, i64) -> i64,
+    float_op: fn(f64, f64) -> f64,
+) -> Step {
+    let (lhs, rhs) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+    let res = numeric_binop(lhs, rhs, mc, int_op, float_op);
+    match res {
+        Ok(val) => {
+            m.push(val);
+            Step::Continue(())
         }
-        if let (Some(a), Some(b)) = (ctx.get_string(lhs), ctx.get_string(rhs)) {
-            self.push(Value::new_inline(pred(a.cmp(b))));
-            return Ok(());
-        }
-        if let (Some(a), Some(b)) = (lhs.as_inline::<Path>(), rhs.as_inline::<Path>()) {
-            let a = ctx.resolve_string(a.0);
-            let b = ctx.resolve_string(b.0);
-            self.push(Value::new_inline(pred(a.cmp(b))));
-            return Ok(());
-        }
-        // TODO: compare other types
-        Err(crate::vm_err(format!(
-            "cannot compare {} with {}",
-            lhs.ty(),
-            rhs.ty()
-        )))
+        Err(e) => m.finish_vm_err(e),
     }
 }
 
+#[inline(always)]
+pub(crate) fn op_div<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let (lhs, rhs) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+    match (get_num(lhs), get_num(rhs)) {
+        (_, Some(NixNum::Int(0))) | (_, Some(NixNum::Float(0.))) => {
+            return m.finish_vm_err(VmError::Uncatchable(fix_error::Error::eval_error(
+                "division by zero",
+            )));
+        }
+        _ => {}
+    }
+    let res = numeric_binop(lhs, rhs, mc, |a, b| a / b, |a, b| a / b);
+    match res {
+        Ok(val) => {
+            m.push(val);
+            Step::Continue(())
+        }
+        Err(e) => m.finish_vm_err(e),
+    }
+}
+
+#[inline(always)]
+pub(crate) fn op_eq<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let (lhs, rhs) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+    crate::primops::start_eq(m, ctx, reader, mc, lhs, rhs, false)
+}
+
+#[inline(always)]
+pub(crate) fn op_neq<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let (lhs, rhs) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+    crate::primops::start_eq(m, ctx, reader, mc, lhs, rhs, true)
+}
+
+#[inline(always)]
+pub(crate) fn op_lt<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    compare_values(m, ctx, reader, mc, Ordering::is_lt)
+}
+
+#[inline(always)]
+pub(crate) fn op_gt<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    compare_values(m, ctx, reader, mc, Ordering::is_gt)
+}
+
+#[inline(always)]
+pub(crate) fn op_leq<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    compare_values(m, ctx, reader, mc, Ordering::is_le)
+}
+
+#[inline(always)]
+pub(crate) fn op_geq<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    compare_values(m, ctx, reader, mc, Ordering::is_ge)
+}
+
+fn compare_values<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+    pred: fn(Ordering) -> bool,
+) -> Step {
+    let (lhs, rhs) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+    match compare_values_inner(m, ctx, pred, lhs, rhs) {
+        Ok(()) => Step::Continue(()),
+        Err(e) => m.finish_vm_err(e),
+    }
+}
+
+#[inline(always)]
+pub(crate) fn op_concat<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let (l, r) = m.force_and_retry::<(Gc<List>, Gc<List>)>(reader, mc)?;
+    let mut items = smallvec::SmallVec::new();
+    items.extend_from_slice(&l.inner.borrow());
+    items.extend_from_slice(&r.inner.borrow());
+    m.push(Value::new_gc(Gc::new(
+        mc,
+        crate::List {
+            inner: RefLock::new(items),
+        },
+    )));
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_update<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let (l, r) = m.force_and_retry::<(Gc<AttrSet>, Gc<AttrSet>)>(reader, mc)?;
+    m.push(Value::new_gc(l.merge(&r, mc)));
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_neg<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let rhs = m.force_and_retry::<NixNum>(reader, mc)?;
+    match rhs {
+        NixNum::Int(int) => m.push(Value::make_int(-int, mc)),
+        NixNum::Float(float) => m.push(Value::new_float(-float)),
+    }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_not<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let rhs = m.force_and_retry::<bool>(reader, mc)?;
+    m.push(Value::new_inline(!rhs));
+    Step::Continue(())
+}
+
+fn compare_values_inner<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &impl VmRuntimeCtx,
+    pred: fn(Ordering) -> bool,
+    lhs: StrictValue<'gc>,
+    rhs: StrictValue<'gc>,
+) -> crate::VmResult<()> {
+    if let (Some(a), Some(b)) = (get_num(lhs), get_num(rhs)) {
+        let ord = match (a, b) {
+            (NixNum::Int(a), NixNum::Int(b)) => a.cmp(&b),
+            (NixNum::Float(a), NixNum::Float(b)) => a.partial_cmp(&b).unwrap_or(Ordering::Less),
+            (NixNum::Int(a), NixNum::Float(b)) => {
+                (a as f64).partial_cmp(&b).unwrap_or(Ordering::Less)
+            }
+            (NixNum::Float(a), NixNum::Int(b)) => {
+                a.partial_cmp(&(b as f64)).unwrap_or(Ordering::Less)
+            }
+        };
+        m.push(Value::new_inline(pred(ord)));
+        return Ok(());
+    }
+    if let (Some(a), Some(b)) = (ctx.get_string(lhs), ctx.get_string(rhs)) {
+        m.push(Value::new_inline(pred(a.cmp(b))));
+        return Ok(());
+    }
+    if let (Some(a), Some(b)) = (lhs.as_inline::<Path>(), rhs.as_inline::<Path>()) {
+        let a = ctx.resolve_string(a.0);
+        let b = ctx.resolve_string(b.0);
+        m.push(Value::new_inline(pred(a.cmp(b))));
+        return Ok(());
+    }
+    // TODO: compare other types
+    Err(crate::vm_err(format!(
+        "cannot compare {} with {}",
+        lhs.ty(),
+        rhs.ty()
+    )))
+}
+
 pub(crate) fn get_num(val: StrictValue<'_>) -> Option<NixNum> {
     if let Some(i) = val.as_inline::<i32>() {
         Some(NixNum::Int(i64::from(i)))

fix-vm/src/instructions/calls.rs

@@ -8,176 +8,174 @@ use crate::{
     VmRuntimeCtxExt,
 };
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn call(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-        arg: Value<'gc>,
-        resume_pc: usize,
-    ) -> Step {
-        let func = self.force_and_retry::<StrictValue>(reader, mc)?;
-        if self.call_depth > 10000 {
-            return self.finish_err(Error::eval_error("stack overflow; max-call-depth exceeded"));
+#[inline(always)]
+pub(crate) fn call<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+    arg: Value<'gc>,
+    resume_pc: usize,
+) -> Step {
+    let func = m.force_and_retry::<StrictValue>(reader, mc)?;
+    if m.call_depth() > 10000 {
+        return m.finish_err(Error::eval_error("stack overflow; max-call-depth exceeded"));
+    }
+    m.inc_call_depth();
+    if let Some(closure) = func.as_gc::<Closure>() {
+        if closure.pattern.is_some() {
+            // FIXME: better DX...
+            m.push(func.relax());
+            m.push(arg);
+            m.push_call_frame(CallFrame {
+                pc: resume_pc,
+                thunk: None,
+                env: m.env(),
+            });
+            reader.set_pc(PrimOpPhase::CallPattern.ip() as usize);
+            return Step::Continue(());
         }
-        self.call_depth += 1;
-        if let Some(closure) = func.as_gc::<Closure>() {
-            if closure.pattern.is_some() {
-                // FIXME: better DX...
-                self.push(func.relax());
-                self.push(arg);
-                self.call_stack.push(CallFrame {
-                    pc: resume_pc,
-                    thunk: None,
-                    env: self.env,
-                });
-                reader.set_pc(PrimOpPhase::CallPattern.ip() as usize);
+
+        let ip = closure.ip;
+        let n_locals = closure.n_locals;
+        let env = closure.env;
+        let new_env = Gc::new(mc, RefLock::new(Env::with_arg(arg, n_locals, env)));
+        m.push_call_frame(CallFrame {
+            pc: resume_pc,
+            thunk: None,
+            env: m.env(),
+        });
+        reader.set_pc(ip as usize);
+        m.set_env(new_env);
+    } else if let Some(primop) = func.as_inline::<PrimOp>() {
+        if primop.arity == 1 {
+            m.push(arg);
+            m.push_call_frame(CallFrame {
+                pc: resume_pc,
+                thunk: None,
+                env: m.env(),
+            });
+            reader.set_pc(primop.dispatch_ip as usize)
+        } else {
+            let app = PrimOpApp {
+                primop,
+                arity: primop.arity - 1,
+                args: [arg, Value::default(), Value::default()],
+            };
+            m.push(Value::new_gc(Gc::new(mc, app)));
+        }
+    } else if let Some(app) = func.as_gc::<PrimOpApp>() {
+        if app.arity == 1 {
+            for i in 0..app.primop.arity - 1 {
+                m.push(app.args[i as usize]);
+            }
+            m.push(arg);
+            m.push_call_frame(CallFrame {
+                pc: resume_pc,
+                thunk: None,
+                env: m.env(),
+            });
+            reader.set_pc(app.primop.dispatch_ip as usize)
+        } else {
+            let position = (app.primop.arity - app.arity) as usize;
+            let mut new_app = PrimOpApp {
+                arity: app.arity - 1,
+                ..*app
+            };
+            new_app.args[position] = arg;
+            m.push(Value::new_gc(Gc::new(mc, new_app)))
+        }
+    } else if let Some(attrs) = func.as_gc::<AttrSet>()
+        && let Some(functor) = attrs.lookup(m.functor_sym())
+    {
+        // f arg  =>  (f.__functor f) arg
+        //
+        // Stage the work for `CallFunctor1` so retries during force are
+        // safe: the stack invariant `[..., orig_arg, self, functor]`
+        // holds every time control re-enters phase 1.
+        m.dec_call_depth();
+        m.push_call_frame(CallFrame {
+            pc: resume_pc,
+            thunk: None,
+            env: m.env(),
+        });
+        m.push(arg);
+        m.push(func.relax());
+        m.push(functor);
+        reader.set_pc(PrimOpPhase::CallFunctor1.ip() as usize);
+        return Step::Continue(());
+    } else {
+        return m.finish_err(Error::eval_error(format!(
+            "attempt to call something which is not a function but {}",
+            func.ty()
+        )));
+    }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_call<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let arg = resolve_operand(&reader.read_operand_data(), mc, ctx, m);
+    let pc = reader.pc();
+    m.call(reader, mc, arg, pc)
+}
+
+#[inline(always)]
+pub(crate) fn op_return<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let val = m.force_and_retry::<StrictValue>(reader, mc)?;
+    let Some(CallFrame {
+        pc: ret_pc,
+        thunk,
+        env,
+    }) = m.pop_call_frame()
+    else {
+        match m.force_mode() {
+            ForceMode::AsIs => return m.finish_ok(ctx.convert_value(val.relax())),
+            ForceMode::Shallow => {
+                m.push(val.relax());
+                reader.set_pc(PrimOpPhase::ForceResultShallow.ip() as usize);
                 return Step::Continue(());
             }
-
-            let ip = closure.ip;
-            let n_locals = closure.n_locals;
-            let env = closure.env;
-            let new_env = Gc::new(mc, RefLock::new(Env::with_arg(arg, n_locals, env)));
-            self.call_stack.push(CallFrame {
-                pc: resume_pc,
-                thunk: None,
-                env: self.env,
-            });
-            reader.set_pc(ip as usize);
-            self.env = new_env;
-        } else if let Some(primop) = func.as_inline::<PrimOp>() {
-            if primop.arity == 1 {
-                self.push(arg);
-                self.call_stack.push(CallFrame {
-                    pc: resume_pc,
+            ForceMode::Deep => {
+                m.push(val.relax());
+                m.push(val.relax());
+                m.push_call_frame(CallFrame {
+                    pc: PrimOpPhase::ForceResultDeepFinish.ip() as usize,
                     thunk: None,
-                    env: self.env,
+                    env: m.env(),
                 });
-                reader.set_pc(primop.dispatch_ip as usize)
-            } else {
-                let app = PrimOpApp {
-                    primop,
-                    arity: primop.arity - 1,
-                    args: [arg, Value::default(), Value::default()],
-                };
-                self.push(Value::new_gc(Gc::new(mc, app)));
+                m.inc_call_depth();
+                reader.set_pc(PrimOpPhase::DeepSeq.ip() as usize);
+                return Step::Continue(());
             }
-        } else if let Some(app) = func.as_gc::<PrimOpApp>() {
-            if app.arity == 1 {
-                for i in 0..app.primop.arity - 1 {
-                    self.push(app.args[i as usize]);
-                }
-                self.push(arg);
-                self.call_stack.push(CallFrame {
-                    pc: resume_pc,
-                    thunk: None,
-                    env: self.env,
-                });
-                reader.set_pc(app.primop.dispatch_ip as usize)
-            } else {
-                let position = (app.primop.arity - app.arity) as usize;
-                let mut new_app = PrimOpApp {
-                    arity: app.arity - 1,
-                    ..*app
-                };
-                new_app.args[position] = arg;
-                self.push(Value::new_gc(Gc::new(mc, new_app)))
-            }
-        } else if let Some(attrs) = func.as_gc::<AttrSet>()
-            && let Some(functor) = attrs.lookup(self.functor_sym)
-        {
-            // f arg  =>  (f.__functor f) arg
-            //
-            // Stage the work for `CallFunctor1` so retries during force are
-            // safe: the stack invariant `[..., orig_arg, self, functor]`
-            // holds every time control re-enters phase 1.
-            self.call_depth -= 1;
-            self.call_stack.push(CallFrame {
-                pc: resume_pc,
-                thunk: None,
-                env: self.env,
-            });
-            self.push(arg);
-            self.push(func.relax());
-            self.push(functor);
-            reader.set_pc(PrimOpPhase::CallFunctor1.ip() as usize);
-            return Step::Continue(());
-        } else {
-            return self.finish_err(Error::eval_error(format!(
-                "attempt to call something which is not a function but {}",
-                func.ty()
-            )));
         }
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_call(
-        &mut self,
-        ctx: &impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let arg = resolve_operand(&reader.read_operand_data(), mc, ctx, self);
-        let pc = reader.pc();
-        self.call(reader, mc, arg, pc)
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_return(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let val = self.force_and_retry::<StrictValue>(reader, mc)?;
-        let Some(CallFrame {
-            pc: ret_pc,
-            thunk,
-            env,
-        }) = self.call_stack.pop()
-        else {
-            match self.force_mode {
-                ForceMode::AsIs => return self.finish_ok(ctx.convert_value(val.relax())),
-                ForceMode::Shallow => {
-                    self.push(val.relax());
-                    reader.set_pc(PrimOpPhase::ForceResultShallow.ip() as usize);
-                    return Step::Continue(());
-                }
-                ForceMode::Deep => {
-                    self.push(val.relax());
-                    self.push(val.relax());
-                    self.call_stack.push(CallFrame {
-                        pc: PrimOpPhase::ForceResultDeepFinish.ip() as usize,
-                        thunk: None,
-                        env: self.env,
-                    });
-                    self.call_depth += 1;
-                    reader.set_pc(PrimOpPhase::DeepSeq.ip() as usize);
-                    return Step::Continue(());
-                }
-            }
-        };
-        reader.set_pc(ret_pc);
-        if let Some(outer_thunk) = thunk {
-            *outer_thunk.borrow_mut(mc) = ThunkState::Evaluated(val);
-        } else {
-            self.call_depth -= 1;
-            self.push(val.relax())
-        }
-        self.env = env;
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_dispatch_primop(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        crate::primops::dispatch_primop(self, ctx, reader, mc)
+    };
+    reader.set_pc(ret_pc);
+    if let Some(outer_thunk) = thunk {
+        *outer_thunk.borrow_mut(mc) = ThunkState::Evaluated(val);
+    } else {
+        m.dec_call_depth();
+        m.push(val.relax())
     }
+    m.set_env(env);
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_dispatch_primop<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    crate::primops::dispatch_primop(m, ctx, reader, mc)
 }

fix-vm/src/instructions/closures.rs

@@ -1,94 +1,93 @@
+use fix_runtime::Machine;
 use gc_arena::{Gc, Mutation, RefLock};
 
 use crate::{BytecodeReader, Step, ThunkState, Value};
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn op_make_thunk(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let entry_point = reader.read_u32();
-        let thunk = Gc::new(
-            mc,
-            RefLock::new(ThunkState::Pending {
-                ip: entry_point as usize,
-                env: self.env,
-            }),
-        );
-        self.push(Value::new_gc(thunk));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_make_thunk<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let entry_point = reader.read_u32();
+    let thunk = Gc::new(
+        mc,
+        RefLock::new(ThunkState::Pending {
+            ip: entry_point as usize,
+            env: m.env(),
+        }),
+    );
+    m.push(Value::new_gc(thunk));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_make_closure(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let entry_point = reader.read_u32();
-        let n_locals = reader.read_u32();
-        let closure = Gc::new(
-            mc,
-            crate::Closure {
-                ip: entry_point,
-                n_locals,
-                env: self.env,
-                pattern: None,
-            },
-        );
-        self.push(Value::new_gc(closure));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_make_closure<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let entry_point = reader.read_u32();
+    let n_locals = reader.read_u32();
+    let closure = Gc::new(
+        mc,
+        crate::Closure {
+            ip: entry_point,
+            n_locals,
+            env: m.env(),
+            pattern: None,
+        },
+    );
+    m.push(Value::new_gc(closure));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_make_pattern_closure(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let entry_point = reader.read_u32();
-        let n_locals = reader.read_u32();
-        let req_count = reader.read_u16() as usize;
-        let opt_count = reader.read_u16() as usize;
-        let has_ellipsis = reader.read_u8() != 0;
+#[inline(always)]
+pub(crate) fn op_make_pattern_closure<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let entry_point = reader.read_u32();
+    let n_locals = reader.read_u32();
+    let req_count = reader.read_u16() as usize;
+    let opt_count = reader.read_u16() as usize;
+    let has_ellipsis = reader.read_u8() != 0;
 
-        let mut required = smallvec::SmallVec::new();
-        for _ in 0..req_count {
-            required.push(reader.read_string_id());
-        }
-        let mut optional = smallvec::SmallVec::new();
-        for _ in 0..opt_count {
-            optional.push(reader.read_string_id());
-        }
-        let total = req_count + opt_count;
-        let mut param_spans = Vec::with_capacity(total);
-        for _ in 0..total {
-            let name = reader.read_string_id();
-            let span_id = reader.read_u32();
-            param_spans.push((name, span_id));
-        }
+    let mut required = smallvec::SmallVec::new();
+    for _ in 0..req_count {
+        required.push(reader.read_string_id());
+    }
+    let mut optional = smallvec::SmallVec::new();
+    for _ in 0..opt_count {
+        optional.push(reader.read_string_id());
+    }
+    let total = req_count + opt_count;
+    let mut param_spans = Vec::with_capacity(total);
+    for _ in 0..total {
+        let name = reader.read_string_id();
+        let span_id = reader.read_u32();
+        param_spans.push((name, span_id));
+    }
 
-        let pattern = Gc::new(
-            mc,
-            crate::PatternInfo {
-                required,
-                optional,
-                ellipsis: has_ellipsis,
-                param_spans: param_spans.into_boxed_slice(),
-            },
-        );
-        let closure = Gc::new(
-            mc,
-            crate::Closure {
-                ip: entry_point,
-                n_locals,
-                env: self.env,
-                pattern: Some(pattern),
-            },
-        );
-        self.push(Value::new_gc(closure));
-        Step::Continue(())
-    }
+    let pattern = Gc::new(
+        mc,
+        crate::PatternInfo {
+            required,
+            optional,
+            ellipsis: has_ellipsis,
+            param_spans: param_spans.into_boxed_slice(),
+        },
+    );
+    let closure = Gc::new(
+        mc,
+        crate::Closure {
+            ip: entry_point,
+            n_locals,
+            env: m.env(),
+            pattern: Some(pattern),
+        },
+    );
+    m.push(Value::new_gc(closure));
+    Step::Continue(())
 }

fix-vm/src/instructions/collections.rs

@@ -1,6 +1,6 @@
 use fix_error::Error;
 use fix_lang::StringId;
-use fix_runtime::{NixType, resolve_operand};
+use fix_runtime::{Machine, MachineExt, NixType, resolve_operand};
 use gc_arena::{Gc, RefLock};
 use smallvec::SmallVec;
 
@@ -8,327 +8,330 @@ use crate::{
     AttrSet, BytecodeReader, List, Step, StrictValue, Value, VmRuntimeCtx, VmRuntimeCtxExt,
 };
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn op_make_attrs(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let static_count = reader.read_u32() as usize;
-        let dynamic_count = reader.read_u32() as usize;
+#[inline(always)]
+pub(crate) fn op_make_attrs<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let static_count = reader.read_u32() as usize;
+    let dynamic_count = reader.read_u32() as usize;
 
-        for i in 0..dynamic_count {
-            let depth = dynamic_count - 1 - i;
-            self.force_slot_to_pc(depth, reader, mc, reader.inst_start_pc())?;
-        }
-
-        let mut dyn_keys: SmallVec<[_; 2]> = SmallVec::with_capacity(dynamic_count);
-        for i in 0..dynamic_count {
-            let depth = dynamic_count - 1 - i;
-            let key_val = self.peek_forced(depth);
-            let key_sid = match ctx.get_string_id(key_val) {
-                Ok(id) => Some(id),
-                Err(NixType::Null) => None,
-                Err(got) => return self.finish_type_err(NixType::String, got),
-            };
-            dyn_keys.push(key_sid);
-        }
-
-        self.stack.truncate(self.stack.len() - dynamic_count);
-
-        let mut kv: SmallVec<[(crate::StringId, Value); 4]> =
-            SmallVec::with_capacity(static_count + dynamic_count);
-
-        for _ in 0..static_count {
-            let key = reader.read_string_id();
-            let val = resolve_operand(&reader.read_operand_data(), mc, ctx, self);
-            let _span_id = reader.read_u32();
-            kv.push((key, val));
-        }
-
-        for key in dyn_keys {
-            let val = resolve_operand(&reader.read_operand_data(), mc, ctx, self);
-            let _span_id = reader.read_u32();
-            if let Some(key) = key {
-                kv.push((key, val))
-            }
-        }
-
-        kv.sort_by_key(|(k, _)| *k);
-        let attrs = Gc::new(mc, AttrSet::from_sorted_unchecked(kv));
-        self.push(Value::new_gc(attrs));
-        Step::Continue(())
+    for i in 0..dynamic_count {
+        let depth = dynamic_count - 1 - i;
+        m.force_slot_to_pc(depth, reader, mc, reader.inst_start_pc())?;
     }
 
-    #[inline(always)]
-    pub(crate) fn op_make_empty_attrs(&mut self) -> Step {
-        self.push(self.empty_attrs);
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_select_static(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let _span_id = reader.read_u32();
-        let key = reader.read_string_id();
-
-        let attrset = self.force_and_retry::<Gc<AttrSet>>(reader, mc)?;
-
-        match attrset.lookup(key) {
-            Some(v) => {
-                self.push(v);
-            }
-            None => return self.select_skip(key, ctx, reader),
-        }
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_select_dynamic(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let _span_id = reader.read_u32();
-
-        let (attrset, key_val) = self.force_and_retry::<(Gc<AttrSet>, StrictValue)>(reader, mc)?;
-
+    let mut dyn_keys: SmallVec<[_; 2]> = SmallVec::with_capacity(dynamic_count);
+    for i in 0..dynamic_count {
+        let depth = dynamic_count - 1 - i;
+        let key_val = m.peek_forced(depth);
         let key_sid = match ctx.get_string_id(key_val) {
-            Ok(id) => id,
-            Err(got) => return self.finish_type_err(NixType::String, got),
+            Ok(id) => Some(id),
+            Err(NixType::Null) => None,
+            Err(got) => return m.finish_type_err(NixType::String, got),
         };
-
-        match attrset.lookup(key_sid) {
-            Some(v) => {
-                self.push(v);
-            }
-            None => return self.select_skip(key_sid, ctx, reader),
-        }
-        Step::Continue(())
+        dyn_keys.push(key_sid);
     }
 
-    /// Skip the rest of a **Select** attrpath after a missing attribute.
-    /// Only recognises Select opcodes and jumps; encountering any other
-    /// opcode means we've reached the end of the select sequence and
-    /// should report the missing-attribute error.
-    fn select_skip(
-        &mut self,
-        key: StringId,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-    ) -> Step {
-        use fix_bytecode::Op::*;
-        loop {
-            match reader.read_op() {
-                SelectStatic => {
-                    reader.set_pc(reader.pc() + 4 + 4);
-                }
-                SelectDynamic => {
-                    reader.set_pc(reader.pc() + 4);
-                }
-                JumpIfSelectSucceeded => {
-                    reader.set_pc(reader.pc() + 4);
-                    break Step::Continue(());
-                }
-                JumpIfSelectFailed => {
-                    let offset = reader.read_i32();
-                    reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
-                }
-                _ => {
-                    let name = ctx.resolve_string(key);
-                    return self
-                        .finish_err(Error::eval_error(format!("attribute '{name}' missing")));
-                }
-            }
-        }
-    }
+    m.drop_n(dynamic_count);
 
-    /// Skip the rest of a **HasAttr** attrpath after an intermediate
-    /// lookup failed. Only recognises HasAttr opcodes and jumps.
-    fn has_attr_skip(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        use fix_bytecode::Op::*;
-        loop {
-            match reader.read_op() {
-                HasAttrPathStatic => {
-                    reader.set_pc(reader.pc() + 4 + 4);
-                }
-                HasAttrPathDynamic => {
-                    reader.set_pc(reader.pc() + 4);
-                }
-                HasAttrStatic => {
-                    reader.set_pc(reader.pc() + 4);
-                    break Step::Continue(());
-                }
-                JumpIfSelectFailed => {
-                    let offset = reader.read_i32();
-                    reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
-                }
-                HasAttrDynamic => {
-                    break Step::Continue(());
-                }
-                HasAttrResolve => {
-                    reader.set_pc(reader.pc() - 1);
-                    break Step::Continue(());
-                }
-                other => {
-                    unreachable!("unexpected opcode {:?} in has_attr_skip", other as u8)
-                }
-            }
-        }
-    }
+    let mut kv: SmallVec<[(crate::StringId, Value); 4]> =
+        SmallVec::with_capacity(static_count + dynamic_count);
 
-    #[inline(always)]
-    pub(crate) fn op_has_attr_path_static(
-        &mut self,
-        _ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let _span_id = reader.read_u32();
+    for _ in 0..static_count {
         let key = reader.read_string_id();
-
-        let current = self.force_and_retry::<StrictValue>(reader, mc)?;
-
-        match current
-            .as_gc::<AttrSet>()
-            .and_then(|attrs| attrs.lookup(key))
-        {
-            Some(v) => {
-                self.push(v);
-            }
-            None => return self.has_attr_skip(reader),
-        }
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_has_attr_path_dynamic(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
+        let val = resolve_operand(&reader.read_operand_data(), mc, ctx, m);
         let _span_id = reader.read_u32();
+        kv.push((key, val));
+    }
 
-        let (current, key_val) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+    for key in dyn_keys {
+        let val = resolve_operand(&reader.read_operand_data(), mc, ctx, m);
+        let _span_id = reader.read_u32();
+        if let Some(key) = key {
+            kv.push((key, val))
+        }
+    }
 
-        let key_sid = match ctx.get_string_id(key_val) {
-            Ok(id) => id,
-            Err(got) => return self.finish_type_err(NixType::String, got),
-        };
+    kv.sort_by_key(|(k, _)| *k);
+    let attrs = Gc::new(mc, AttrSet::from_sorted_unchecked(kv));
+    m.push(Value::new_gc(attrs));
+    Step::Continue(())
+}
 
-        match current
-            .as_gc::<AttrSet>()
-            .and_then(|attrs| attrs.lookup(key_sid))
-        {
-            Some(v) => {
-                self.push(v);
+#[inline(always)]
+pub(crate) fn op_make_empty_attrs<'gc, M: Machine<'gc>>(m: &mut M) -> Step {
+    m.push(m.empty_attrs());
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_select_static<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let _span_id = reader.read_u32();
+    let key = reader.read_string_id();
+
+    let attrset = m.force_and_retry::<Gc<AttrSet>>(reader, mc)?;
+
+    match attrset.lookup(key) {
+        Some(v) => {
+            m.push(v);
+        }
+        None => return select_skip(m, key, ctx, reader),
+    }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_select_dynamic<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let _span_id = reader.read_u32();
+
+    let (attrset, key_val) = m.force_and_retry::<(Gc<AttrSet>, StrictValue)>(reader, mc)?;
+
+    let key_sid = match ctx.get_string_id(key_val) {
+        Ok(id) => id,
+        Err(got) => return m.finish_type_err(NixType::String, got),
+    };
+
+    match attrset.lookup(key_sid) {
+        Some(v) => {
+            m.push(v);
+        }
+        None => return select_skip(m, key_sid, ctx, reader),
+    }
+    Step::Continue(())
+}
+
+/// Skip the rest of a **Select** attrpath after a missing attribute.
+/// Only recognises Select opcodes and jumps; encountering any other
+/// opcode means we've reached the end of the select sequence and
+/// should report the missing-attribute error.
+fn select_skip<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    key: StringId,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    use fix_bytecode::Op::*;
+    loop {
+        match reader.read_op() {
+            SelectStatic => {
+                reader.set_pc(reader.pc() + 4 + 4);
+            }
+            SelectDynamic => {
+                reader.set_pc(reader.pc() + 4);
+            }
+            JumpIfSelectSucceeded => {
+                reader.set_pc(reader.pc() + 4);
+                break Step::Continue(());
+            }
+            JumpIfSelectFailed => {
+                let offset = reader.read_i32();
+                reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
+            }
+            _ => {
+                let name = ctx.resolve_string(key);
+                return m.finish_err(Error::eval_error(format!("attribute '{name}' missing")));
             }
-            None => return self.has_attr_skip(reader),
         }
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_jump_if_select_failed(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        // No-op
-        let _offset = reader.read_i32();
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_jump_if_select_succeeded(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        let offset = reader.read_i32();
-        reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_has_attr_static(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let key = reader.read_string_id();
-        let current = self.force_and_retry::<StrictValue>(reader, mc)?;
-
-        self.push(Value::new_inline(
-            current
-                .as_gc::<AttrSet>()
-                .and_then(|attrs| attrs.lookup(key))
-                .is_some(),
-        ));
-        // Skip HasAttrResolve
-        reader.set_pc(reader.pc() + 1);
-
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_has_attr_dynamic(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let (current, dyn_key) = self.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
-
-        let key_sid = match ctx.get_string_id(dyn_key) {
-            Ok(id) => id,
-            Err(got) => return self.finish_type_err(NixType::String, got),
-        };
-
-        self.push(Value::new_inline(
-            current
-                .as_gc::<AttrSet>()
-                .and_then(|attrs| attrs.lookup(key_sid))
-                .is_some(),
-        ));
-        // Skip HasAttrResolve
-        reader.set_pc(reader.pc() + 1);
-
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_has_attr_resolve(&mut self) -> Step {
-        // If we reach here, has_attr check has failed, push false (AttrSet is already popped)
-        self.push(Value::new_inline(false));
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_make_list(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let count = reader.read_u32() as usize;
-        let mut items: SmallVec<[Value; 4]> = SmallVec::with_capacity(count);
-        for _ in 0..count {
-            items.push(resolve_operand(&reader.read_operand_data(), mc, ctx, self));
-        }
-        let list = Gc::new(
-            mc,
-            List {
-                inner: RefLock::new(items),
-            },
-        );
-        self.push(Value::new_gc(list));
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_make_empty_list(&mut self) -> Step {
-        self.push(self.empty_list);
-        Step::Continue(())
     }
 }
+
+/// Skip the rest of a **HasAttr** attrpath after an intermediate
+/// lookup failed. Only recognises HasAttr opcodes and jumps.
+fn has_attr_skip(reader: &mut BytecodeReader<'_>) -> Step {
+    use fix_bytecode::Op::*;
+    loop {
+        match reader.read_op() {
+            HasAttrPathStatic => {
+                reader.set_pc(reader.pc() + 4 + 4);
+            }
+            HasAttrPathDynamic => {
+                reader.set_pc(reader.pc() + 4);
+            }
+            HasAttrStatic => {
+                reader.set_pc(reader.pc() + 4);
+                break Step::Continue(());
+            }
+            JumpIfSelectFailed => {
+                let offset = reader.read_i32();
+                reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
+            }
+            HasAttrDynamic => {
+                break Step::Continue(());
+            }
+            HasAttrResolve => {
+                reader.set_pc(reader.pc() - 1);
+                break Step::Continue(());
+            }
+            other => {
+                unreachable!("unexpected opcode {:?} in has_attr_skip", other as u8)
+            }
+        }
+    }
+}
+
+#[inline(always)]
+pub(crate) fn op_has_attr_path_static<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    _ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let _span_id = reader.read_u32();
+    let key = reader.read_string_id();
+
+    let current = m.force_and_retry::<StrictValue>(reader, mc)?;
+
+    match current
+        .as_gc::<AttrSet>()
+        .and_then(|attrs| attrs.lookup(key))
+    {
+        Some(v) => {
+            m.push(v);
+        }
+        None => return has_attr_skip(reader),
+    }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_has_attr_path_dynamic<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let _span_id = reader.read_u32();
+
+    let (current, key_val) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+
+    let key_sid = match ctx.get_string_id(key_val) {
+        Ok(id) => id,
+        Err(got) => return m.finish_type_err(NixType::String, got),
+    };
+
+    match current
+        .as_gc::<AttrSet>()
+        .and_then(|attrs| attrs.lookup(key_sid))
+    {
+        Some(v) => {
+            m.push(v);
+        }
+        None => return has_attr_skip(reader),
+    }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_jump_if_select_failed<'gc, M: Machine<'gc>>(
+    _m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    // No-op
+    let _offset = reader.read_i32();
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_jump_if_select_succeeded<'gc, M: Machine<'gc>>(
+    _m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    let offset = reader.read_i32();
+    reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_has_attr_static<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let key = reader.read_string_id();
+    let current = m.force_and_retry::<StrictValue>(reader, mc)?;
+
+    m.push(Value::new_inline(
+        current
+            .as_gc::<AttrSet>()
+            .and_then(|attrs| attrs.lookup(key))
+            .is_some(),
+    ));
+    // Skip HasAttrResolve
+    reader.set_pc(reader.pc() + 1);
+
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_has_attr_dynamic<'gc, M: MachineExt<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let (current, dyn_key) = m.force_and_retry::<(StrictValue, StrictValue)>(reader, mc)?;
+
+    let key_sid = match ctx.get_string_id(dyn_key) {
+        Ok(id) => id,
+        Err(got) => return m.finish_type_err(NixType::String, got),
+    };
+
+    m.push(Value::new_inline(
+        current
+            .as_gc::<AttrSet>()
+            .and_then(|attrs| attrs.lookup(key_sid))
+            .is_some(),
+    ));
+    // Skip HasAttrResolve
+    reader.set_pc(reader.pc() + 1);
+
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_has_attr_resolve<'gc, M: Machine<'gc>>(m: &mut M) -> Step {
+    // If we reach here, has_attr check has failed, push false (AttrSet is already popped)
+    m.push(Value::new_inline(false));
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_make_list<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let count = reader.read_u32() as usize;
+    let mut items: SmallVec<[Value; 4]> = SmallVec::with_capacity(count);
+    for _ in 0..count {
+        items.push(resolve_operand(&reader.read_operand_data(), mc, ctx, m));
+    }
+    let list = Gc::new(
+        mc,
+        List {
+            inner: RefLock::new(items),
+        },
+    );
+    m.push(Value::new_gc(list));
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_make_empty_list<'gc, M: Machine<'gc>>(m: &mut M) -> Step {
+    m.push(m.empty_list());
+    Step::Continue(())
+}

fix-vm/src/instructions/control.rs

@@ -4,57 +4,55 @@ use gc_arena::Mutation;
 
 use crate::{BytecodeReader, Step, VmRuntimeCtx};
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn op_jump_if_false(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let offset = reader.read_i32();
-        let cond = self.force_and_retry::<StrictValue>(reader, mc)?;
-        if cond.as_inline::<bool>() == Some(false) {
-            reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
-        }
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_jump_if_true(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let offset = reader.read_i32();
-        let cond = self.force_and_retry::<StrictValue>(reader, mc)?;
-        if cond.as_inline::<bool>() == Some(true) {
-            reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
-        }
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_jump(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        let offset = reader.read_i32();
+#[inline(always)]
+pub(crate) fn op_jump_if_false<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let offset = reader.read_i32();
+    let cond = m.force_and_retry::<StrictValue>(reader, mc)?;
+    if cond.as_inline::<bool>() == Some(false) {
         reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_assert(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let raw_id = reader.read_string_id();
-        let raw = ctx.resolve_string(raw_id);
-        let _span_id = reader.read_u32();
-        let assertion = self.force_and_retry::<bool>(reader, mc)?;
-        if !assertion {
-            // FIXME: use catchable error
-            return self.finish_err(Error::eval_error(format!("assertion '{raw}' failed")));
-        }
-        Step::Continue(())
     }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_jump_if_true<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let offset = reader.read_i32();
+    let cond = m.force_and_retry::<StrictValue>(reader, mc)?;
+    if cond.as_inline::<bool>() == Some(true) {
+        reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
+    }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_jump<'gc, M: Machine<'gc>>(_m: &mut M, reader: &mut BytecodeReader<'_>) -> Step {
+    let offset = reader.read_i32();
+    reader.set_pc(((reader.pc() as isize) + (offset as isize)) as usize);
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_assert<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let raw_id = reader.read_string_id();
+    let raw = ctx.resolve_string(raw_id);
+    let _span_id = reader.read_u32();
+    let assertion = m.force_and_retry::<bool>(reader, mc)?;
+    if !assertion {
+        // FIXME: use catchable error
+        return m.finish_err(Error::eval_error(format!("assertion '{raw}' failed")));
+    }
+    Step::Continue(())
 }

fix-vm/src/instructions/literals.rs

@@ -1,55 +1,63 @@
+use fix_runtime::Machine;
 use gc_arena::{Gc, Mutation};
 
 use crate::{BytecodeReader, Step, Value};
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn op_push_smi(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        let val = reader.read_i32();
-        self.push(Value::new_inline(val));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_push_smi<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    let val = reader.read_i32();
+    m.push(Value::new_inline(val));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_push_bigint(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        let val = reader.read_i64();
-        self.push(Value::new_gc(Gc::new(mc, val)));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_push_bigint<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &Mutation<'gc>,
+) -> Step {
+    let val = reader.read_i64();
+    m.push(Value::new_gc(Gc::new(mc, val)));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_push_float(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        let val = reader.read_f64();
-        self.push(Value::new_float(val));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_push_float<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    let val = reader.read_f64();
+    m.push(Value::new_float(val));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_push_string(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        let sid = reader.read_string_id();
-        self.push(Value::new_inline(sid));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_push_string<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    let sid = reader.read_string_id();
+    m.push(Value::new_inline(sid));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_push_null(&mut self) -> Step {
-        self.push(Value::new_inline(crate::Null));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_push_null<'gc, M: Machine<'gc>>(m: &mut M) -> Step {
+    m.push(Value::new_inline(crate::Null));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_push_true(&mut self) -> Step {
-        self.push(Value::new_inline(true));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_push_true<'gc, M: Machine<'gc>>(m: &mut M) -> Step {
+    m.push(Value::new_inline(true));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_push_false(&mut self) -> Step {
-        self.push(Value::new_inline(false));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_push_false<'gc, M: Machine<'gc>>(m: &mut M) -> Step {
+    m.push(Value::new_inline(false));
+    Step::Continue(())
 }

fix-vm/src/instructions/misc.rs

@@ -3,165 +3,164 @@ use std::path::PathBuf;
 use fix_bytecode::PrimOpPhase;
 use fix_error::Error;
 use fix_lang::{BUILTINS, BuiltinId, StringId};
-use fix_runtime::{AttrSet, NixString, Path, StrictValue, StringContext, canon_path_str};
+use fix_runtime::{
+    AttrSet, Machine, MachineExt, NixString, Path, StrictValue, StringContext, canon_path_str,
+};
 use num_enum::TryFromPrimitive;
 
 use crate::{BytecodeReader, PrimOp, Step, Value, VmRuntimeCtx, VmRuntimeCtxExt};
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn op_load_builtins(&mut self) -> Step {
-        self.push(self.builtins);
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_load_builtins<'gc, M: Machine<'gc>>(m: &mut M) -> Step {
+    m.push(m.builtins());
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_load_builtin(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        let Ok(id) = BuiltinId::try_from_primitive(reader.read_u8())
-            .map_err(|err| panic!("unknown builtin id: {}", err.number));
-        self.push(Value::new_inline(PrimOp {
-            id,
-            arity: BUILTINS[id as usize].1,
-            dispatch_ip: PrimOpPhase::entry_for_builtin(id).ip(),
-        }));
-        Step::Continue(())
-    }
+#[inline(always)]
+pub(crate) fn op_load_builtin<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    let Ok(id) = BuiltinId::try_from_primitive(reader.read_u8())
+        .map_err(|err| panic!("unknown builtin id: {}", err.number));
+    m.push(Value::new_inline(PrimOp {
+        id,
+        arity: BUILTINS[id as usize].1,
+        dispatch_ip: PrimOpPhase::entry_for_builtin(id).ip(),
+    }));
+    Step::Continue(())
+}
 
-    #[inline(always)]
-    pub(crate) fn op_load_repl_binding(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
-        let _name = reader.read_string_id();
-        todo!("LoadReplBinding");
-    }
+#[inline(always)]
+pub(crate) fn op_load_repl_binding<'gc, M: Machine<'gc>>(
+    _m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+) -> Step {
+    let _name = reader.read_string_id();
+    todo!("LoadReplBinding");
+}
 
-    #[inline(always)]
-    pub(crate) fn op_load_scoped_binding(
-        &mut self,
-        ctx: &impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        _mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let slot_id = reader.read_u32();
-        let name = reader.read_string_id();
-        let scope = match self.scope_slots.get(slot_id as usize).copied() {
-            Some(s) => s,
-            None => {
-                return self.finish_err(Error::eval_error(format!(
-                    "internal: invalid scope slot {slot_id}"
-                )));
-            }
-        };
-        let Some(attrs) = scope.as_gc::<AttrSet>() else {
-            return self.finish_err(Error::eval_error("internal: scope slot is not an attrset"));
-        };
-        match attrs.lookup(name) {
-            Some(val) => {
-                self.push(val);
-                Step::Continue(())
-            }
-            None => self.finish_err(Error::eval_error(format!(
-                "scoped binding '{}' not found",
-                ctx.resolve_string(name)
-            ))),
+#[inline(always)]
+pub(crate) fn op_load_scoped_binding<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    _mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let slot_id = reader.read_u32();
+    let name = reader.read_string_id();
+    let scope = m.scope_slot(slot_id);
+    let Some(attrs) = scope.as_gc::<AttrSet>() else {
+        return m.finish_err(Error::eval_error("internal: scope slot is not an attrset"));
+    };
+    match attrs.lookup(name) {
+        Some(val) => {
+            m.push(val);
+            Step::Continue(())
+        }
+        None => m.finish_err(Error::eval_error(format!(
+            "scoped binding '{}' not found",
+            ctx.resolve_string(name)
+        ))),
+    }
+}
+
+#[inline(always)]
+pub(crate) fn op_coerce_to_string<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let val = m.force_and_retry::<StrictValue>(reader, mc)?;
+    if val.is::<StringId>() || val.is::<NixString>() {
+        m.push(val.relax());
+    } else if let Some(p) = val.as_inline::<Path>() {
+        // Coercing a path to a string yields the canonical path text.
+        // FIXME: copy to store
+        m.push(Value::new_inline(p.0));
+    } else {
+        todo!("coerce other types to string: {:?}", val.ty());
+    }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_concat_strings<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let count = reader.read_u16() as usize;
+    let _force_string = reader.read_u8() != 0;
+
+    let mut total_len = 0;
+    let mut has_any_context = false;
+    for i in 0..count {
+        let val = m.peek_forced(count - 1 - i);
+        let s = ctx.get_string(val).expect("coerced");
+        total_len += s.len();
+        if !ctx.get_string_context(val).is_empty() {
+            has_any_context = true;
         }
     }
 
-    #[inline(always)]
-    pub(crate) fn op_coerce_to_string(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let val = self.force_and_retry::<StrictValue>(reader, mc)?;
-        if val.is::<StringId>() || val.is::<NixString>() {
-            self.push(val.relax());
-        } else if let Some(p) = val.as_inline::<Path>() {
-            // Coercing a path to a string yields the canonical path text.
-            // FIXME: copy to store
-            self.push(Value::new_inline(p.0));
-        } else {
-            todo!("coerce other types to string: {:?}", val.ty());
-        }
-        Step::Continue(())
-    }
-
-    #[inline(always)]
-    pub(crate) fn op_concat_strings(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let count = reader.read_u16() as usize;
-        let _force_string = reader.read_u8() != 0;
-
-        let mut total_len = 0;
-        let mut has_any_context = false;
-        for i in 0..count {
-            let val = self.peek_forced(count - 1 - i);
-            let s = ctx.get_string(val).expect("coerced");
-            total_len += s.len();
-            if !ctx.get_string_context(val).is_empty() {
-                has_any_context = true;
+    let mut result = String::with_capacity(total_len);
+    let mut merged = StringContext::new();
+    for i in 0..count {
+        let val = m.peek_forced(count - 1 - i);
+        let s = ctx.get_string(val).expect("coerced");
+        result.push_str(s);
+        if has_any_context {
+            let ctx = ctx.get_string_context(val);
+            if !ctx.is_empty() {
+                merged = merged.merge(ctx);
             }
         }
-
-        let mut result = String::with_capacity(total_len);
-        let mut merged = StringContext::new();
-        for i in 0..count {
-            let val = self.peek_forced(count - 1 - i);
-            let s = ctx.get_string(val).expect("coerced");
-            result.push_str(s);
-            if has_any_context {
-                let ctx = ctx.get_string_context(val);
-                if !ctx.is_empty() {
-                    merged = merged.merge(ctx);
-                }
-            }
-        }
-
-        self.stack.truncate(self.stack.len() - count);
-
-        if merged.is_empty() {
-            let sid = ctx.intern_string(result);
-            self.push(Value::new_inline(sid));
-        } else {
-            let ns = gc_arena::Gc::new(mc, NixString::with_context(result, merged));
-            self.push(Value::new_gc(ns));
-        }
-        Step::Continue(())
     }
 
-    #[inline(always)]
-    pub(crate) fn op_resolve_path(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        let path_val = self.force_and_retry::<StrictValue>(reader, mc)?;
-        let dir_id = reader.read_string_id();
-        // Already a path: keep as-is. ResolvePath is idempotent on paths.
-        if let Some(p) = path_val.as_inline::<Path>() {
-            self.push(Value::new_inline(p));
-            return Step::Continue(());
-        }
-        let path = match ctx.get_string(path_val) {
-            Some(s) => s.to_owned(),
-            None => {
-                return self.finish_err(Error::eval_error(format!(
-                    "expected a string for path, got {}",
-                    path_val.ty()
-                )));
-            }
-        };
-        let resolved = match resolve_path_str(ctx.resolve_string(dir_id), &path) {
-            Ok(s) => s,
-            Err(e) => return self.finish_err(e),
-        };
-        let sid = ctx.intern_string(resolved);
-        self.push(Value::new_inline(Path(sid)));
-        Step::Continue(())
+    m.drop_n(count);
+
+    if merged.is_empty() {
+        let sid = ctx.intern_string(result);
+        m.push(Value::new_inline(sid));
+    } else {
+        let ns = gc_arena::Gc::new(mc, NixString::with_context(result, merged));
+        m.push(Value::new_gc(ns));
     }
+    Step::Continue(())
+}
+
+#[inline(always)]
+pub(crate) fn op_resolve_path<'gc, M: MachineExt<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    let path_val = m.force_and_retry::<StrictValue>(reader, mc)?;
+    let dir_id = reader.read_string_id();
+    // Already a path: keep as-is. ResolvePath is idempotent on paths.
+    if let Some(p) = path_val.as_inline::<Path>() {
+        m.push(Value::new_inline(p));
+        return Step::Continue(());
+    }
+    let path = match ctx.get_string(path_val) {
+        Some(s) => s.to_owned(),
+        None => {
+            return m.finish_err(Error::eval_error(format!(
+                "expected a string for path, got {}",
+                path_val.ty()
+            )));
+        }
+    };
+    let resolved = match resolve_path_str(ctx.resolve_string(dir_id), &path) {
+        Ok(s) => s,
+        Err(e) => return m.finish_err(e),
+    };
+    let sid = ctx.intern_string(resolved);
+    m.push(Value::new_inline(Path(sid)));
+    Step::Continue(())
 }
 
 fn resolve_path_str(current_dir: &str, path: &str) -> Result<String, Box<Error>> {

fix-vm/src/instructions/mod.rs

@@ -7,3 +7,13 @@ pub(crate) mod literals;
 pub(crate) mod misc;
 pub(crate) mod variables;
 pub(crate) mod with_scope;
+
+pub(crate) use arithmetic::*;
+pub(crate) use calls::*;
+pub(crate) use closures::*;
+pub(crate) use collections::*;
+pub(crate) use control::*;
+pub(crate) use literals::*;
+pub(crate) use misc::*;
+pub(crate) use variables::*;
+pub(crate) use with_scope::*;

fix-vm/src/instructions/variables.rs

@@ -1,50 +1,48 @@
+use fix_runtime::Machine;
+
 use crate::{BytecodeReader, Mutation, Step, Value};
 
-impl<'gc> crate::Vm<'gc> {
     #[inline(always)]
-    pub(crate) fn op_load_local(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
+    pub(crate) fn op_load_local<'gc, M: Machine<'gc>>(m: &mut M, reader: &mut BytecodeReader<'_>) -> Step {
         let idx = reader.read_u32() as usize;
-        self.push(self.env.borrow().locals[idx]);
+        m.push(m.env().borrow().locals[idx]);
         Step::Continue(())
     }
 
     #[inline(always)]
-    pub(crate) fn op_load_outer(&mut self, reader: &mut BytecodeReader<'_>) -> Step {
+    pub(crate) fn op_load_outer<'gc, M: Machine<'gc>>(m: &mut M, reader: &mut BytecodeReader<'_>) -> Step {
         let layer = reader.read_u8();
         let idx = reader.read_u32() as usize;
-        let mut cur = self.env;
+        let mut cur = m.env();
         for _ in 0..layer {
             let prev = cur.borrow().prev.expect("LoadOuter: env chain too short");
             cur = prev;
         }
         let val = cur.borrow().locals[idx];
-        self.push(val);
+        m.push(val);
         Step::Continue(())
     }
 
     #[inline(always)]
-    pub(crate) fn op_store_local(
-        &mut self,
+    pub(crate) fn op_store_local<'gc, M: Machine<'gc>>(m: &mut M,
         reader: &mut BytecodeReader<'_>,
         mc: &Mutation<'gc>,
     ) -> Step {
         let idx = reader.read_u32() as usize;
-        let val = self.pop();
-        self.env.borrow_mut(mc).locals[idx] = val;
+        let val = m.pop();
+        m.env().borrow_mut(mc).locals[idx] = val;
         Step::Continue(())
     }
 
     #[inline(always)]
-    pub(crate) fn op_alloc_locals(
-        &mut self,
+    pub(crate) fn op_alloc_locals<'gc, M: Machine<'gc>>(m: &mut M,
         reader: &mut BytecodeReader<'_>,
         mc: &Mutation<'gc>,
     ) -> Step {
         let count = reader.read_u32() as usize;
-        self.env
+        m.env()
             .borrow_mut(mc)
             .locals
             .extend(std::iter::repeat_n(Value::default(), count));
         Step::Continue(())
     }
-}

fix-vm/src/instructions/with_scope.rs

@@ -5,74 +5,71 @@ use smallvec::SmallVec;
 
 use crate::{Break, BytecodeReader, CallFrame, Step, VmRuntimeCtx};
 
-impl<'gc> crate::Vm<'gc> {
-    #[inline(always)]
-    pub(crate) fn op_lookup_with(
-        &mut self,
-        ctx: &mut impl VmRuntimeCtx,
-        reader: &mut BytecodeReader<'_>,
-        mc: &gc_arena::Mutation<'gc>,
-    ) -> Step {
-        #[allow(clippy::unwrap_used)]
-        let counter = self.peek_forced(0).as_inline::<i32>().unwrap();
+#[inline(always)]
+pub(crate) fn op_lookup_with<'gc, M: Machine<'gc>>(
+    m: &mut M,
+    ctx: &mut impl VmRuntimeCtx,
+    reader: &mut BytecodeReader<'_>,
+    mc: &gc_arena::Mutation<'gc>,
+) -> Step {
+    #[allow(clippy::unwrap_used)]
+    let counter = m.peek_forced(0).as_inline::<i32>().unwrap();
 
-        let name = reader.read_string_id();
-        let n = reader.read_u8();
-        let mut namespaces = SmallVec::<[_; 2]>::new();
-        for _ in 0..n {
-            namespaces.push(resolve_operand(&reader.read_operand_data(), mc, ctx, self));
-        }
+    let name = reader.read_string_id();
+    let n = reader.read_u8();
+    let mut namespaces = SmallVec::<[_; 2]>::new();
+    for _ in 0..n {
+        namespaces.push(resolve_operand(&reader.read_operand_data(), mc, ctx, m));
+    }
 
-        let resume_pc = reader.inst_start_pc();
-        let namespace = match namespaces[counter as usize].restrict() {
-            Ok(val) => val,
-            Err(thunk) => {
-                let mut state = thunk.borrow_mut(mc);
-                match *state {
-                    ThunkState::Pending { ip, env } => {
-                        *state = ThunkState::Blackhole;
-                        self.call_stack.push(CallFrame {
-                            thunk: Some(thunk),
-                            pc: resume_pc,
-                            env: self.env,
-                        });
-                        self.env = env;
-                        reader.set_pc(ip);
-                        return Step::Break(Break::Force);
-                    }
-                    ThunkState::Evaluated(v) => v,
-                    ThunkState::Apply { func, arg } => {
-                        self.call_stack.push(CallFrame {
-                            thunk: Some(thunk),
-                            pc: resume_pc,
-                            env: self.env,
-                        });
-                        self.push(func);
-                        return self.call(reader, mc, arg, resume_pc);
-                    }
-                    ThunkState::Blackhole => {
-                        return self
-                            .finish_err(Error::eval_error("infinite recursion encountered"));
-                    }
+    let resume_pc = reader.inst_start_pc();
+    let namespace = match namespaces[counter as usize].restrict() {
+        Ok(val) => val,
+        Err(thunk) => {
+            let mut state = thunk.borrow_mut(mc);
+            match *state {
+                ThunkState::Pending { ip, env } => {
+                    *state = ThunkState::Blackhole;
+                    m.push_call_frame(CallFrame {
+                        thunk: Some(thunk),
+                        pc: resume_pc,
+                        env: m.env(),
+                    });
+                    m.set_env(env);
+                    reader.set_pc(ip);
+                    return Step::Break(Break::Force);
+                }
+                ThunkState::Evaluated(v) => v,
+                ThunkState::Apply { func, arg } => {
+                    m.push_call_frame(CallFrame {
+                        thunk: Some(thunk),
+                        pc: resume_pc,
+                        env: m.env(),
+                    });
+                    m.push(func);
+                    return m.call(reader, mc, arg, resume_pc);
+                }
+                ThunkState::Blackhole => {
+                    return m.finish_err(Error::eval_error("infinite recursion encountered"));
                 }
             }
-        };
-
-        if let Some(val) = namespace
-            .as_gc::<AttrSet>()
-            .and_then(|attrs| attrs.lookup(name))
-        {
-            self.replace(0, val);
-        } else if counter + 1 == n as i32 {
-            return self.finish_err(Error::eval_error(format!(
-                "undefined variable '{}'",
-                Symbol::from(ctx.resolve_string(name))
-            )));
-        } else {
-            self.replace(0, Value::new_inline(counter + 1));
-            reader.set_pc(resume_pc);
         }
+    };
 
-        Step::Continue(())
+    if let Some(val) = namespace
+        .as_gc::<AttrSet>()
+        .and_then(|attrs| attrs.lookup(name))
+    {
+        m.replace(0, val);
+    } else if counter + 1 == n as i32 {
+        return m.finish_err(Error::eval_error(format!(
+            "undefined variable '{}'",
+            Symbol::from(ctx.resolve_string(name))
+        )));
+    } else {
+        m.replace(0, Value::new_inline(counter + 1));
+        reader.set_pc(resume_pc);
     }
+
+    Step::Continue(())
 }

fix-vm/src/lib.rs

@@ -137,45 +137,20 @@ impl<'gc> Vm<'gc> {
             functor_sym: ctx.intern_string("__functor"),
         }
     }
+}
 
-    #[inline(always)]
-    fn finish_ok(&mut self, val: fix_lang::Value) -> Step {
-        self.result = Some(Ok(val));
-        Step::Break(Break::Done)
-    }
-
-    #[inline(always)]
-    fn finish_err(&mut self, err: Box<Error>) -> Step {
-        self.result = Some(Err(err));
-        Step::Break(Break::Done)
-    }
-
-    #[inline(always)]
-    fn finish_type_err(&mut self, expected: NixType, got: NixType) -> Step {
-        self.result = Some(Err(Error::eval_error(format!(
-            "expected {expected}, got {got}"
-        ))));
-        Step::Break(Break::Done)
-    }
-
-    #[inline(always)]
-    fn finish_vm_err(&mut self, err: VmError) -> Step {
-        self.finish_err(err.into_error())
-    }
-
+impl<'gc> Machine<'gc> for Vm<'gc> {
     #[inline(always)]
     fn push(&mut self, val: Value<'gc>) {
         self.stack.push(val);
     }
 
     #[inline(always)]
-    #[must_use]
     fn pop(&mut self) -> Value<'gc> {
         self.stack.pop().expect("stack underflow")
     }
 
     #[inline(always)]
-    #[must_use]
     fn peek(&self, depth: usize) -> Value<'gc> {
         *self
             .stack
@@ -184,7 +159,6 @@ impl<'gc> Vm<'gc> {
     }
 
     #[inline(always)]
-    #[must_use]
     fn peek_forced(&self, depth: usize) -> StrictValue<'gc> {
         self.stack
             .get(self.stack.len() - depth - 1)
@@ -193,6 +167,15 @@ impl<'gc> Vm<'gc> {
             .expect("forced")
     }
 
+    #[inline(always)]
+    fn pop_forced(&mut self) -> StrictValue<'gc> {
+        self.stack
+            .pop()
+            .expect("stack underflow")
+            .restrict()
+            .expect("forced")
+    }
+
     #[inline(always)]
     fn replace(&mut self, depth: usize, val: Value<'gc>) {
         let len = self.stack.len();
@@ -203,72 +186,13 @@ impl<'gc> Vm<'gc> {
     }
 
     #[inline(always)]
-    #[cfg_attr(debug_assertions, track_caller)]
-    fn pop_forced(&mut self) -> StrictValue<'gc> {
-        self.stack
-            .pop()
-            .expect("stack underflow")
-            .restrict()
-            .expect("forced")
-    }
-
-    /// Force the top `T::WIDTH` stack slots and return them as `T`.
-    ///
-    /// If any slot holds a pending thunk, this method pushes a call frame
-    /// whose resume PC is the **start of the current instruction**
-    /// (`reader.inst_start_pc()`), enters the thunk, and returns
-    /// `Break::Force`.  When the thunk eventually returns, the VM will
-    /// **re-execute the entire opcode handler from the beginning**.
-    ///
-    /// # Invariants
-    ///
-    /// * **Do not call this method more than once in a single handler.**
-    ///   If you need to force multiple values, use a tuple type such as
-    ///   `(StrictValue, StrictValue)` so they are forced and popped in one
-    ///   atomic operation.  Calling `force_and_retry` twice (or more)
-    ///   means the handler will be re-run from the top after each retry;
-    ///   any stack modifications between the two calls would be duplicated
-    ///   and corrupt the stack layout.
-    ///
-    /// * The caller must ensure that the stack layout at the point of
-    ///   invocation is **identical** every time the handler is re-entered.
-    ///   In practice this means no pushes, pops, or local mutations may
-    ///   happen before the call, and the call must be the first thing
-    ///   that consumes the instruction's operand values.
-    ///
-    /// * The return value must be propagated with `?` so that
-    ///   `Break::Force` correctly unwinds to the dispatch loop.
-    #[inline(always)]
-    fn force_and_retry<T: Forced<'gc>>(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> std::ops::ControlFlow<Break, T> {
-        self.force_and_retry_pc(reader, mc, reader.inst_start_pc())
-    }
-
-    /// Same as [`force_and_retry`](Self::force_and_retry) but allows
-    /// specifying a custom resume PC.
-    #[inline(always)]
-    fn force_and_retry_pc<T: Forced<'gc>>(
-        &mut self,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-        resume_pc: usize,
-    ) -> std::ops::ControlFlow<Break, T> {
-        T::force_and_check(self, reader, mc, 0, resume_pc)?;
-        std::ops::ControlFlow::Continue(T::pop_converted(self))
+    fn drop_n(&mut self, depth: usize) {
+        self.stack.truncate(self.stack.len() - depth);
     }
 
     #[inline(always)]
-    #[allow(unused)]
-    fn force_slot(
-        &mut self,
-        depth: usize,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-    ) -> Step {
-        self.force_slot_to_pc(depth, reader, mc, reader.inst_start_pc())
+    fn stack_len(&self) -> usize {
+        self.stack.len()
     }
 
     #[inline(always)]
@@ -313,54 +237,6 @@ impl<'gc> Vm<'gc> {
             }
         }
     }
-}
-
-impl<'gc> Machine<'gc> for Vm<'gc> {
-    #[inline(always)]
-    fn push(&mut self, val: Value<'gc>) {
-        self.push(val);
-    }
-
-    #[inline(always)]
-    fn pop(&mut self) -> Value<'gc> {
-        self.pop()
-    }
-
-    #[inline(always)]
-    fn peek(&self, depth: usize) -> Value<'gc> {
-        Vm::peek(self, depth)
-    }
-
-    #[inline(always)]
-    fn peek_forced(&self, depth: usize) -> StrictValue<'gc> {
-        Vm::peek_forced(self, depth)
-    }
-
-    #[inline(always)]
-    fn pop_forced(&mut self) -> StrictValue<'gc> {
-        self.pop_forced()
-    }
-
-    #[inline(always)]
-    fn replace(&mut self, depth: usize, val: Value<'gc>) {
-        self.replace(depth, val);
-    }
-
-    #[inline(always)]
-    fn stack_len(&self) -> usize {
-        self.stack.len()
-    }
-
-    #[inline(always)]
-    fn force_slot_to_pc(
-        &mut self,
-        depth: usize,
-        reader: &mut BytecodeReader<'_>,
-        mc: &Mutation<'gc>,
-        resume_pc: usize,
-    ) -> Step {
-        self.force_slot_to_pc(depth, reader, mc, resume_pc)
-    }
 
     #[inline(always)]
     fn call(
@@ -370,7 +246,7 @@ impl<'gc> Machine<'gc> for Vm<'gc> {
         arg: Value<'gc>,
         resume_pc: usize,
     ) -> Step {
-        self.call(reader, mc, arg, resume_pc)
+        instructions::call(self, reader, mc, arg, resume_pc)
     }
 
     #[inline(always)]
@@ -410,17 +286,22 @@ impl<'gc> Machine<'gc> for Vm<'gc> {
 
     #[inline(always)]
     fn finish_ok(&mut self, val: fix_lang::Value) -> Step {
-        self.finish_ok(val)
+        self.result = Some(Ok(val));
+        Step::Break(Break::Done)
     }
 
     #[inline(always)]
     fn finish_err(&mut self, err: Box<Error>) -> Step {
-        self.finish_err(err)
+        self.result = Some(Err(err));
+        Step::Break(Break::Done)
     }
 
     #[inline(always)]
     fn finish_type_err(&mut self, expected: NixType, got: NixType) -> Step {
-        self.finish_type_err(expected, got)
+        self.result = Some(Err(Error::eval_error(format!(
+            "expected {expected}, got {got}"
+        ))));
+        Step::Break(Break::Done)
     }
 
     #[inline(always)]
@@ -590,6 +471,7 @@ impl<'gc> Vm<'gc> {
         mc: &Mutation<'gc>,
     ) -> Action {
         use fix_bytecode::Op::*;
+        use instructions::*;
 
         let mut reader = BytecodeReader::new(bytecode, pc);
         let mut fuel = Self::DEFAULT_FUEL_AMOUNT;
@@ -603,75 +485,75 @@ impl<'gc> Vm<'gc> {
             let op = reader.read_op();
 
             let result = match op {
-                PushSmi => self.op_push_smi(&mut reader),
-                PushBigInt => self.op_push_bigint(&mut reader, mc),
-                PushFloat => self.op_push_float(&mut reader),
-                PushString => self.op_push_string(&mut reader),
-                PushNull => self.op_push_null(),
-                PushTrue => self.op_push_true(),
-                PushFalse => self.op_push_false(),
+                PushSmi => op_push_smi(self, &mut reader),
+                PushBigInt => op_push_bigint(self, &mut reader, mc),
+                PushFloat => op_push_float(self, &mut reader),
+                PushString => op_push_string(self, &mut reader),
+                PushNull => op_push_null(self),
+                PushTrue => op_push_true(self),
+                PushFalse => op_push_false(self),
 
-                LoadLocal => self.op_load_local(&mut reader),
-                LoadOuter => self.op_load_outer(&mut reader),
-                StoreLocal => self.op_store_local(&mut reader, mc),
-                AllocLocals => self.op_alloc_locals(&mut reader, mc),
+                LoadLocal => op_load_local(self, &mut reader),
+                LoadOuter => op_load_outer(self, &mut reader),
+                StoreLocal => op_store_local(self, &mut reader, mc),
+                AllocLocals => op_alloc_locals(self, &mut reader, mc),
 
-                MakeThunk => self.op_make_thunk(&mut reader, mc),
-                MakeClosure => self.op_make_closure(&mut reader, mc),
-                MakePatternClosure => self.op_make_pattern_closure(&mut reader, mc),
+                MakeThunk => op_make_thunk(self, &mut reader, mc),
+                MakeClosure => op_make_closure(self, &mut reader, mc),
+                MakePatternClosure => op_make_pattern_closure(self, &mut reader, mc),
 
-                Call => self.op_call(ctx, &mut reader, mc),
-                DispatchPrimOp => self.op_dispatch_primop(ctx, &mut reader, mc),
-                Return => self.op_return(ctx, &mut reader, mc),
+                Call => op_call(self, ctx, &mut reader, mc),
+                DispatchPrimOp => op_dispatch_primop(self, ctx, &mut reader, mc),
+                Return => op_return(self, ctx, &mut reader, mc),
 
-                MakeAttrs => self.op_make_attrs(ctx, &mut reader, mc),
-                MakeEmptyAttrs => self.op_make_empty_attrs(),
-                SelectStatic => self.op_select_static(ctx, &mut reader, mc),
-                SelectDynamic => self.op_select_dynamic(ctx, &mut reader, mc),
-                HasAttrPathStatic => self.op_has_attr_path_static(ctx, &mut reader, mc),
-                HasAttrPathDynamic => self.op_has_attr_path_dynamic(ctx, &mut reader, mc),
-                HasAttrStatic => self.op_has_attr_static(&mut reader, mc),
-                HasAttrDynamic => self.op_has_attr_dynamic(ctx, &mut reader, mc),
-                HasAttrResolve => self.op_has_attr_resolve(),
-                JumpIfSelectFailed => self.op_jump_if_select_failed(&mut reader),
-                JumpIfSelectSucceeded => self.op_jump_if_select_succeeded(&mut reader),
+                MakeAttrs => op_make_attrs(self, ctx, &mut reader, mc),
+                MakeEmptyAttrs => op_make_empty_attrs(self),
+                SelectStatic => op_select_static(self, ctx, &mut reader, mc),
+                SelectDynamic => op_select_dynamic(self, ctx, &mut reader, mc),
+                HasAttrPathStatic => op_has_attr_path_static(self, ctx, &mut reader, mc),
+                HasAttrPathDynamic => op_has_attr_path_dynamic(self, ctx, &mut reader, mc),
+                HasAttrStatic => op_has_attr_static(self, &mut reader, mc),
+                HasAttrDynamic => op_has_attr_dynamic(self, ctx, &mut reader, mc),
+                HasAttrResolve => op_has_attr_resolve(self),
+                JumpIfSelectFailed => op_jump_if_select_failed(self, &mut reader),
+                JumpIfSelectSucceeded => op_jump_if_select_succeeded(self, &mut reader),
 
-                MakeList => self.op_make_list(ctx, &mut reader, mc),
-                MakeEmptyList => self.op_make_empty_list(),
+                MakeList => op_make_list(self, ctx, &mut reader, mc),
+                MakeEmptyList => op_make_empty_list(self),
 
-                OpAdd => self.op_add(ctx, &mut reader, mc),
-                OpSub => self.op_sub(&mut reader, mc),
-                OpMul => self.op_mul(&mut reader, mc),
-                OpDiv => self.op_div(&mut reader, mc),
-                OpEq => self.op_eq(ctx, &mut reader, mc),
-                OpNeq => self.op_neq(ctx, &mut reader, mc),
-                OpLt => self.op_lt(ctx, &mut reader, mc),
-                OpGt => self.op_gt(ctx, &mut reader, mc),
-                OpLeq => self.op_leq(ctx, &mut reader, mc),
-                OpGeq => self.op_geq(ctx, &mut reader, mc),
-                OpConcat => self.op_concat(&mut reader, mc),
-                OpUpdate => self.op_update(&mut reader, mc),
+                OpAdd => op_add(self, ctx, &mut reader, mc),
+                OpSub => op_sub(self, &mut reader, mc),
+                OpMul => op_mul(self, &mut reader, mc),
+                OpDiv => op_div(self, &mut reader, mc),
+                OpEq => op_eq(self, ctx, &mut reader, mc),
+                OpNeq => op_neq(self, ctx, &mut reader, mc),
+                OpLt => op_lt(self, ctx, &mut reader, mc),
+                OpGt => op_gt(self, ctx, &mut reader, mc),
+                OpLeq => op_leq(self, ctx, &mut reader, mc),
+                OpGeq => op_geq(self, ctx, &mut reader, mc),
+                OpConcat => op_concat(self, &mut reader, mc),
+                OpUpdate => op_update(self, &mut reader, mc),
 
-                OpNeg => self.op_neg(&mut reader, mc),
-                OpNot => self.op_not(&mut reader, mc),
+                OpNeg => op_neg(self, &mut reader, mc),
+                OpNot => op_not(self, &mut reader, mc),
 
-                JumpIfFalse => self.op_jump_if_false(&mut reader, mc),
-                JumpIfTrue => self.op_jump_if_true(&mut reader, mc),
-                Jump => self.op_jump(&mut reader),
+                JumpIfFalse => op_jump_if_false(self, &mut reader, mc),
+                JumpIfTrue => op_jump_if_true(self, &mut reader, mc),
+                Jump => op_jump(self, &mut reader),
 
-                ConcatStrings => self.op_concat_strings(ctx, &mut reader, mc),
-                CoerceToString => self.op_coerce_to_string(&mut reader, mc),
-                ResolvePath => self.op_resolve_path(ctx, &mut reader, mc),
+                ConcatStrings => op_concat_strings(self, ctx, &mut reader, mc),
+                CoerceToString => op_coerce_to_string(self, &mut reader, mc),
+                ResolvePath => op_resolve_path(self, ctx, &mut reader, mc),
 
-                Assert => self.op_assert(ctx, &mut reader, mc),
+                Assert => op_assert(self, ctx, &mut reader, mc),
 
-                LookupWith => self.op_lookup_with(ctx, &mut reader, mc),
+                LookupWith => op_lookup_with(self, ctx, &mut reader, mc),
 
-                LoadBuiltins => self.op_load_builtins(),
-                LoadBuiltin => self.op_load_builtin(&mut reader),
+                LoadBuiltins => op_load_builtins(self),
+                LoadBuiltin => op_load_builtin(self, &mut reader),
 
-                LoadReplBinding => self.op_load_repl_binding(&mut reader),
-                LoadScopedBinding => self.op_load_scoped_binding(ctx, &mut reader, mc),
+                LoadReplBinding => op_load_repl_binding(self, &mut reader),
+                LoadScopedBinding => op_load_scoped_binding(self, ctx, &mut reader, mc),
 
                 Illegal => unreachable!(),
             };

fix/Cargo.toml

@@ -3,6 +3,18 @@ name = "fix"
 version = "0.1.0"
 edition = "2024"
 
+[[bench]]
+harness = false
+name = "basic_ops"
+
+[[bench]]
+harness = false
+name = "builtins"
+
+[[bench]]
+harness = false
+name = "thunk_scope"
+
 [dependencies]
 mimalloc = "0.1"
 
@@ -17,9 +29,9 @@ clap = { version = "4", features = ["derive"] }
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 
+miette = { version = "7.4", features = ["fancy"] }
 # Error Reporting
 thiserror = "2"
-miette = { version = "7.4", features = ["fancy"] }
 
 # Data Structure
 hashbrown = { workspace = true }
@@ -38,15 +50,3 @@ fix-vm = { path = "../fix-vm" }
 criterion = { version = "0.8", features = ["html_reports"] }
 tempfile = "3.24"
 test-log = { version = "0.2", features = ["trace"] }
-
-[[bench]]
-name = "basic_ops"
-harness = false
-
-[[bench]]
-name = "builtins"
-harness = false
-
-[[bench]]
-name = "thunk_scope"
-harness = false

flake.nix

@@ -47,6 +47,7 @@
               just
               samply
               tokei
+              tombi
 
               # llm-agents.codex
               llm-agents.claude-code

typos.toml

@@ -1,7 +1,7 @@
 [files]
 extend-exclude = [
-    "nix-js/tests/tests/regex.rs",
-    "nix-js/tests/tests/lang",
+  "nix-js/tests/tests/regex.rs",
+  "nix-js/tests/tests/lang",
 ]
 
 [default.extend-words]