From fa73e371894dfe5afff9c93b0be9aa18f0d049db Mon Sep 17 00:00:00 2001
From: "g. nicholas d'andrea" <gnidan@users.noreply.github.com>
Date: Tue, 6 Oct 2026 19:30:52 -0400
Subject: [PATCH] bugc: leave the jump past an inlined return out of the
 inlined body

At optimization levels 2 and 3, the jump from an inlined body to the
caller's continuation runs after the inlined function's return, so it is
the caller's code. It kept a transform: ["inline"] context, so a debugger
that reads the transform put that jump in an inlined body that had
already returned, with no function or call site to name.
---
 packages/bugc/CHANGELOG.md                      |  7 +++++++
 packages/bugc/src/evmgen/inline-bracket.test.ts | 16 ++++++++++++++++
 packages/bugc/src/optimizer/steps/inlining.ts   | 15 +++------------
 3 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/packages/bugc/CHANGELOG.md b/packages/bugc/CHANGELOG.md
index 5eee6e0cc1..7c3ec72bdf 100644
--- a/packages/bugc/CHANGELOG.md
+++ b/packages/bugc/CHANGELOG.md
@@ -69,6 +69,12 @@ support. Changes to the specification itself are tracked in the root
   inlined call, or returns one's result, now has its own `invoke` and
   `return` contexts, around the inner call's. Before, its `invoke` (or its
   `return`) was lost, so the call stack did not balance ([#341]).
+- At optimization levels 2 and 3, the jump that leaves an inlined body
+  for the caller's code no longer has a `transform: ["inline"]` context.
+  It runs after the inlined function's `return`, so it is not part of the
+  inlined body. Before, a debugger that reads the transform put that jump
+  in an inlined body that had already returned, with no function or call
+  site to name ([#347]).
 - A cast from dynamic `bytes` to a fixed-size type now reads the bytes.
   `msg.data[0:4] as bytes4` is the first four bytes of calldata; bytes
   past the slice's length are zero. Before, the cast gave the slice's
@@ -262,3 +268,4 @@ First publication.
 [#343]: https://github.com/ethdebug/format/pull/343
 [#344]: https://github.com/ethdebug/format/pull/344
 [#345]: https://github.com/ethdebug/format/pull/345
+[#347]: https://github.com/ethdebug/format/pull/347
diff --git a/packages/bugc/src/evmgen/inline-bracket.test.ts b/packages/bugc/src/evmgen/inline-bracket.test.ts
index 6583bcfed8..4e399659da 100644
--- a/packages/bugc/src/evmgen/inline-bracket.test.ts
+++ b/packages/bugc/src/evmgen/inline-bracket.test.ts
@@ -129,6 +129,22 @@ describe("inlined invoke/return are bracketed on emitted bytecode", () => {
     expect(t.both).toBe(0);
   });
 
+  it("marks only the body inline, from its invoke to its return", async () => {
+    for (const source of [dblTwoSites, multiInstrBody]) {
+      const instrs = await runtimeInstructions(source, 2);
+      // Ops past a return (the jump back to the caller's continuation)
+      // are the caller's code, not part of the inlined body.
+      let open = 0;
+      const outside: number[] = [];
+      instrs.map(flags).forEach((f, i) => {
+        if (f.invoke) open += 1;
+        if (f.inline && open === 0) outside.push(i);
+        if (f.return) open -= 1;
+      });
+      expect(outside).toEqual([]);
+    }
+  });
+
   it("preserves runtime behavior at every level", async () => {
     for (const level of [0, 1, 2, 3] as const) {
       const res = await executeProgram(dblTwoSites, {
diff --git a/packages/bugc/src/optimizer/steps/inlining.ts b/packages/bugc/src/optimizer/steps/inlining.ts
index daca9f2b62..6335959f30 100644
--- a/packages/bugc/src/optimizer/steps/inlining.ts
+++ b/packages/bugc/src/optimizer/steps/inlining.ts
@@ -220,10 +220,9 @@ export class InliningStep extends BaseOptimizationStep {
     }
     const invokes = [...pendingInvokes, inlineInvoke];
     const returns = [inlineReturn, ...pendingReturns];
-    const returnedJump: Ir.Instruction.Debug = {
-      ...Ir.Utils.addTransform(after, "inline"),
-      ...placement(after),
-    };
+    // The jump back to the continuation runs past the callee's return:
+    // it is the caller's code, with no `inline` transform of its own.
+    const returnedJump: Ir.Instruction.Debug = { ...after };
 
     const entryBlockId = blockRename.get(callee.entry)!;
     const returnBlockIds: string[] = [];
@@ -717,14 +716,6 @@ function withoutActivationsDebug(
   return { ...rest, ...(context ? { context } : {}) };
 }
 
-/** A debug's inline sites and origin, which say where it is */
-function placement(debug: Ir.Instruction.Debug): Ir.Instruction.Debug {
-  return {
-    ...(debug.inlineSites ? { inlineSites: debug.inlineSites } : {}),
-    ...(debug.origin ? { origin: debug.origin } : {}),
-  };
-}
-
 /**
  * Preserve the call site's `code` range on the entry instruction.
  * The instruction already maps to the callee body, so the two source