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From e0bf5646026c2c5f440a7110c6560884bde75964 Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Wed, 23 Sep 2026 14:33:27 +0100
Subject: [PATCH] JavaScriptCore: JSToWasm: load/store all 8 wasm GPR args on
RISCV64
The JS-to-wasm trampoline in JSToWasm.cpp handles register-arg shuffling
across three architectures. ARM64 (8 GPR args) and X86_64 (6 GPR args)
have dedicated branches. RISCV64 also has 8 GPR args (regWA0..regWA7,
a0..a7) but was falling through to the generic USE(JSVALUE64) branch
which only handles 6, leaving regWA6 and regWA7 with stale stack
contents on call entry and dropping them on call return.
Symptom: any wasm function whose calling convention places i32/i64
params in a6 or a7 sees garbage for those args. Reproducer is the
JSC wasm-spec "large-sig" function (17 mixed-type params -- locals
14 and 15 land in a6/a7); also propagates to wasm-to-wasm via JS
import (e.g. spec-tests/func.wast.js #124, memory_trap.wast.js #295).
Add explicit CPU(RISCV64) branches mirroring the X86_64 form but
covering all 8 GPRs. FPRs already had a combined X86_64||RISCV64
branch covering all 8 FPRs, so no change needed there.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
Source/JavaScriptCore/wasm/js/JSToWasm.cpp | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/Source/JavaScriptCore/wasm/js/JSToWasm.cpp
+++ b/Source/JavaScriptCore/wasm/js/JSToWasm.cpp
@@ -324,6 +324,15 @@ MacroAssemblerCodeRef<JITThunkPtrTag> cr
jit.loadPair64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 0 * 8), GPRInfo::regWA0, GPRInfo::regWA1);
jit.loadPair64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 2 * 8), GPRInfo::regWA2, GPRInfo::regWA3);
jit.loadPair64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 4 * 8), GPRInfo::regWA4, GPRInfo::regWA5);
+#elif CPU(RISCV64)
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 0 * 8), GPRInfo::regWA0);
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 1 * 8), GPRInfo::regWA1);
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 2 * 8), GPRInfo::regWA2);
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 3 * 8), GPRInfo::regWA3);
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 4 * 8), GPRInfo::regWA4);
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 5 * 8), GPRInfo::regWA5);
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 6 * 8), GPRInfo::regWA6);
+ jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 7 * 8), GPRInfo::regWA7);
#elif USE(JSVALUE64)
jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 0 * 8), GPRInfo::regWA0);
jit.load64(CCallHelpers::Address(CCallHelpers::stackPointerRegister, 1 * 8), GPRInfo::regWA1);
@@ -410,6 +419,15 @@ MacroAssemblerCodeRef<JITThunkPtrTag> cr
jit.storePair64(GPRInfo::regWA0, GPRInfo::regWA1, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 0 * 8));
jit.storePair64(GPRInfo::regWA2, GPRInfo::regWA3, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 2 * 8));
jit.storePair64(GPRInfo::regWA4, GPRInfo::regWA5, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 4 * 8));
+#elif CPU(RISCV64)
+ jit.store64(GPRInfo::regWA0, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 0 * 8));
+ jit.store64(GPRInfo::regWA1, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 1 * 8));
+ jit.store64(GPRInfo::regWA2, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 2 * 8));
+ jit.store64(GPRInfo::regWA3, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 3 * 8));
+ jit.store64(GPRInfo::regWA4, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 4 * 8));
+ jit.store64(GPRInfo::regWA5, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 5 * 8));
+ jit.store64(GPRInfo::regWA6, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 6 * 8));
+ jit.store64(GPRInfo::regWA7, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 7 * 8));
#elif USE(JSVALUE64)
jit.store64(GPRInfo::regWA0, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 0 * 8));
jit.store64(GPRInfo::regWA1, CCallHelpers::Address(CCallHelpers::stackPointerRegister, 1 * 8));
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