From 1aec858a278e0e476002a7db7be95e522062d245 Mon Sep 17 00:00:00 2001
From: Matthew Schneider <panat.matthew@gmail.com>
Date: Thu, 17 Sep 2026 12:55:32 -0400
Subject: [PATCH 1/2] Clear the `stp` slot in the frame when performing OSR

---
 src/engine/compiler/SinglePassCompiler.v3 |   4 ++++
 test/wizeng/osr_gc.wasm                   | Bin 0 -> 104 bytes
 test/wizeng/osr_gc.wasm.exit              |   1 +
 test/wizeng/osr_gc.wasm.flags             |   1 +
 test/wizeng/osr_gc.wat                    |   7 +++++++
 5 files changed, 13 insertions(+)
 create mode 100644 test/wizeng/osr_gc.wasm
 create mode 100644 test/wizeng/osr_gc.wasm.exit
 create mode 100644 test/wizeng/osr_gc.wasm.flags
 create mode 100644 test/wizeng/osr_gc.wat

diff --git a/src/engine/compiler/SinglePassCompiler.v3 b/src/engine/compiler/SinglePassCompiler.v3
index 8c80f86d6..b35a692ea 100644
--- a/src/engine/compiler/SinglePassCompiler.v3
+++ b/src/engine/compiler/SinglePassCompiler.v3
@@ -2146,6 +2146,10 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
 		if (Trace.compiler) Trace.OUT.put1("  OSR (+%d)", osr_entry_label.create_pos).ln();
 		masm.bindLabel(osr_entry_label);
 		emit_reload_regs();
+		// The interpreter's frame has its sidetable pointer in this slot
+		if (SpcTuning.inlineWhammProbes && SpcTuning.intrinsifyWhammProbe) {
+			masm.emit_mov_m_l(frame.inlined_instance_slot, 0);
+		}
 		for (i < u32.!(state.length)) {
 			var sv = state[i];
 			var iv = SpcVal(sv.kindFlags(IS_STORED | TAG_STORED), NO_REG, 0);
diff --git a/test/wizeng/osr_gc.wasm b/test/wizeng/osr_gc.wasm
new file mode 100644
index 0000000000000000000000000000000000000000..e640d4031b1ac731b1f711da8dbfd9f093fc0aa6
GIT binary patch
literal 104
zcmXBFF$%&k0EW@;Phu@C1wq8cK|F~aJw+Qr43Q>+9RwGz?%-P<ek}szG=tfzdFM~8
ysl7j6Ax<fPHDcS!6`w2WjygzRd);wn)Z@a~-3I!eldHZ&ZG=g|G?GxZ|Cb+_?+=Rr

literal 0
HcmV?d00001

diff --git a/test/wizeng/osr_gc.wasm.exit b/test/wizeng/osr_gc.wasm.exit
new file mode 100644
index 000000000..573541ac9
--- /dev/null
+++ b/test/wizeng/osr_gc.wasm.exit
@@ -0,0 +1 @@
+0
diff --git a/test/wizeng/osr_gc.wasm.flags b/test/wizeng/osr_gc.wasm.flags
new file mode 100644
index 000000000..e827cf200
--- /dev/null
+++ b/test/wizeng/osr_gc.wasm.flags
@@ -0,0 +1 @@
+--expose=wizeng
diff --git a/test/wizeng/osr_gc.wat b/test/wizeng/osr_gc.wat
new file mode 100644
index 000000000..884c1c26e
--- /dev/null
+++ b/test/wizeng/osr_gc.wat
@@ -0,0 +1,7 @@
+(module
+  (import "wizeng" "force_gc" (func $gc))
+  (func (export "main") (local $i i32)
+    ;; the loop tiers up while this frame still holds the interpreter's sidetable pointer
+    (loop $l
+      (call $gc)
+      (br_if $l (i32.lt_u (local.tee $i (i32.add (local.get $i) (i32.const 1))) (i32.const 10))))))

From ab5e8f61cc6db9fca4b3d0d725d1cb99f8ea264c Mon Sep 17 00:00:00 2001
From: Matthew Schneider <panat.matthew@gmail.com>
Date: Thu, 24 Sep 2026 18:00:49 -0400
Subject: [PATCH 2/2] Move comment

---
 src/engine/compiler/SinglePassCompiler.v3 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/engine/compiler/SinglePassCompiler.v3 b/src/engine/compiler/SinglePassCompiler.v3
index 186b25b7e..aca601973 100644
--- a/src/engine/compiler/SinglePassCompiler.v3
+++ b/src/engine/compiler/SinglePassCompiler.v3
@@ -2127,8 +2127,8 @@ class SinglePassCompiler(xenv: SpcExecEnv, masm: MacroAssembler, regAlloc: RegAl
 		if (Trace.compiler) Trace.OUT.put1("  OSR (+%d)", osr_entry_label.create_pos).ln();
 		masm.bindLabel(osr_entry_label);
 		emit_reload_regs();
-		// The interpreter's frame has its sidetable pointer in this slot
 		if (SpcTuning.inlineWhammProbes && SpcTuning.intrinsifyWhammProbe) {
+			// Clear sidetable pointer in this slot
 			masm.emit_mov_m_l(frame.inlined_instance_slot, 0);
 		}
 		for (i < u32.!(state.length)) {