commit 020bda6ff0b5dae780fc2f410c3a3e4d1f0a80a3
parent 395d9507f3e52a314c44e9e6cd31646b200624b4
Author: André Bargull <andre.bargull@gmail.com>
Date: Tue, 11 Nov 2025 12:29:34 +0000
Bug 1998161 - Part 2: Use register allocator to place lhs operand for div/mod into eax. r=spidermonkey-reviewers,iain
Instead of manually moving the lhs operand into `eax`, use `useFixedAtStart`
to perform the register move through the register allocator.
Differential Revision: https://phabricator.services.mozilla.com/D271220
Diffstat:
4 files changed, 30 insertions(+), 70 deletions(-)
diff --git a/js/src/jit/x64/CodeGenerator-x64.cpp b/js/src/jit/x64/CodeGenerator-x64.cpp
@@ -212,7 +212,8 @@ void CodeGenerator::visitDivI64(LDivI64* lir) {
Register lhs = ToRegister(lir->lhs());
Register rhs = ToRegister(lir->rhs());
- MOZ_ASSERT_IF(lhs != rhs, rhs != rax);
+ MOZ_ASSERT(lhs == rax);
+ MOZ_ASSERT(rhs != rax);
MOZ_ASSERT(rhs != rdx);
MOZ_ASSERT(ToRegister(lir->output()) == rax);
MOZ_ASSERT(ToRegister(lir->temp0()) == rdx);
@@ -231,11 +232,6 @@ void CodeGenerator::visitDivI64(LDivI64* lir) {
masm.bind(¬Overflow);
}
- // Put the lhs in rax.
- if (lhs != rax) {
- masm.mov(lhs, rax);
- }
-
// Sign extend the lhs into rdx to make rdx:rax.
masm.cqo();
masm.idivq(rhs);
@@ -246,7 +242,8 @@ void CodeGenerator::visitModI64(LModI64* lir) {
Register rhs = ToRegister(lir->rhs());
Register output = ToRegister(lir->output());
- MOZ_ASSERT_IF(lhs != rhs, rhs != rax);
+ MOZ_ASSERT(lhs == rax);
+ MOZ_ASSERT(rhs != rax);
MOZ_ASSERT(rhs != rdx);
MOZ_ASSERT(ToRegister(lir->output()) == rdx);
MOZ_ASSERT(ToRegister(lir->temp0()) == rax);
@@ -270,11 +267,6 @@ void CodeGenerator::visitModI64(LModI64* lir) {
masm.bind(¬Overflow);
}
- // Put the lhs in rax.
- if (lhs != rax) {
- masm.mov(lhs, rax);
- }
-
// Sign extend the lhs into rdx to make rdx:rax.
masm.cqo();
masm.idivq(rhs);
@@ -283,10 +275,10 @@ void CodeGenerator::visitModI64(LModI64* lir) {
}
void CodeGenerator::visitUDivI64(LUDivI64* lir) {
- Register lhs = ToRegister(lir->lhs());
Register rhs = ToRegister(lir->rhs());
- MOZ_ASSERT_IF(lhs != rhs, rhs != rax);
+ MOZ_ASSERT(ToRegister(lir->lhs()) == rax);
+ MOZ_ASSERT(rhs != rax);
MOZ_ASSERT(rhs != rdx);
MOZ_ASSERT(ToRegister(lir->output()) == rax);
MOZ_ASSERT(ToRegister(lir->temp0()) == rdx);
@@ -294,21 +286,16 @@ void CodeGenerator::visitUDivI64(LUDivI64* lir) {
// Prevent divide by zero.
TrapIfDivideByZero(masm, lir, rhs);
- // Put the lhs in rax.
- if (lhs != rax) {
- masm.mov(lhs, rax);
- }
-
// Zero extend the lhs into rdx to make (rdx:rax).
masm.xorl(rdx, rdx);
masm.udivq(rhs);
}
void CodeGenerator::visitUModI64(LUModI64* lir) {
- Register lhs = ToRegister(lir->lhs());
Register rhs = ToRegister(lir->rhs());
- MOZ_ASSERT_IF(lhs != rhs, rhs != rax);
+ MOZ_ASSERT(ToRegister(lir->lhs()) == rax);
+ MOZ_ASSERT(rhs != rax);
MOZ_ASSERT(rhs != rdx);
MOZ_ASSERT(ToRegister(lir->output()) == rdx);
MOZ_ASSERT(ToRegister(lir->temp0()) == rax);
@@ -316,11 +303,6 @@ void CodeGenerator::visitUModI64(LUModI64* lir) {
// Prevent divide by zero.
TrapIfDivideByZero(masm, lir, rhs);
- // Put the lhs in rax.
- if (lhs != rax) {
- masm.mov(lhs, rax);
- }
-
// Zero extend the lhs into rdx to make (rdx:rax).
masm.xorl(rdx, rdx);
masm.udivq(rhs);
diff --git a/js/src/jit/x64/Lowering-x64.cpp b/js/src/jit/x64/Lowering-x64.cpp
@@ -526,8 +526,8 @@ void LIRGenerator::visitSubstr(MSubstr* ins) {
}
void LIRGeneratorX64::lowerDivI64(MDiv* div) {
- auto* lir = new (alloc())
- LDivI64(useRegister(div->lhs()), useRegister(div->rhs()), tempFixed(rdx));
+ auto* lir = new (alloc()) LDivI64(useFixedAtStart(div->lhs(), rax),
+ useRegister(div->rhs()), tempFixed(rdx));
defineInt64Fixed(lir, div, LInt64Allocation(LAllocation(AnyRegister(rax))));
}
@@ -536,8 +536,8 @@ void LIRGeneratorX64::lowerWasmBuiltinDivI64(MWasmBuiltinDivI64* div) {
}
void LIRGeneratorX64::lowerModI64(MMod* mod) {
- auto* lir = new (alloc())
- LModI64(useRegister(mod->lhs()), useRegister(mod->rhs()), tempFixed(rax));
+ auto* lir = new (alloc()) LModI64(useFixedAtStart(mod->lhs(), rax),
+ useRegister(mod->rhs()), tempFixed(rax));
defineInt64Fixed(lir, mod, LInt64Allocation(LAllocation(AnyRegister(rdx))));
}
@@ -546,13 +546,13 @@ void LIRGeneratorX64::lowerWasmBuiltinModI64(MWasmBuiltinModI64* mod) {
}
void LIRGeneratorX64::lowerUDivI64(MDiv* div) {
- auto* lir = new (alloc()) LUDivI64(useRegister(div->lhs()),
+ auto* lir = new (alloc()) LUDivI64(useFixedAtStart(div->lhs(), rax),
useRegister(div->rhs()), tempFixed(rdx));
defineInt64Fixed(lir, div, LInt64Allocation(LAllocation(AnyRegister(rax))));
}
void LIRGeneratorX64::lowerUModI64(MMod* mod) {
- auto* lir = new (alloc()) LUModI64(useRegister(mod->lhs()),
+ auto* lir = new (alloc()) LUModI64(useFixedAtStart(mod->lhs(), rax),
useRegister(mod->rhs()), tempFixed(rax));
defineInt64Fixed(lir, mod, LInt64Allocation(LAllocation(AnyRegister(rdx))));
}
diff --git a/js/src/jit/x86-shared/CodeGenerator-x86-shared.cpp b/js/src/jit/x86-shared/CodeGenerator-x86-shared.cpp
@@ -897,12 +897,12 @@ OutOfLineCode* CodeGeneratorX86Shared::emitOutOfLineZeroForDivideByZero(
}
void CodeGenerator::visitUDiv(LUDiv* ins) {
- Register lhs = ToRegister(ins->lhs());
Register rhs = ToRegister(ins->rhs());
Register output = ToRegister(ins->output());
Register remainder = ToRegister(ins->temp0());
- MOZ_ASSERT_IF(lhs != rhs, rhs != eax);
+ MOZ_ASSERT(ToRegister(ins->lhs()) == eax);
+ MOZ_ASSERT(rhs != eax);
MOZ_ASSERT(rhs != edx);
MOZ_ASSERT(output == eax);
MOZ_ASSERT(remainder == edx);
@@ -911,11 +911,6 @@ void CodeGenerator::visitUDiv(LUDiv* ins) {
OutOfLineCode* ool = nullptr;
- // Put the lhs in eax.
- if (lhs != eax) {
- masm.mov(lhs, eax);
- }
-
// Prevent divide by zero.
if (mir->canBeDivideByZero()) {
if (mir->trapOnError()) {
@@ -950,11 +945,11 @@ void CodeGenerator::visitUDiv(LUDiv* ins) {
}
void CodeGenerator::visitUMod(LUMod* ins) {
- Register lhs = ToRegister(ins->lhs());
Register rhs = ToRegister(ins->rhs());
Register output = ToRegister(ins->output());
- MOZ_ASSERT_IF(lhs != rhs, rhs != eax);
+ MOZ_ASSERT(ToRegister(ins->lhs()) == eax);
+ MOZ_ASSERT(rhs != eax);
MOZ_ASSERT(rhs != edx);
MOZ_ASSERT(output == edx);
MOZ_ASSERT(ToRegister(ins->temp0()) == eax);
@@ -963,11 +958,6 @@ void CodeGenerator::visitUMod(LUMod* ins) {
OutOfLineCode* ool = nullptr;
- // Put the lhs in eax.
- if (lhs != eax) {
- masm.mov(lhs, eax);
- }
-
// Prevent divide by zero.
if (mir->canBeDivideByZero()) {
if (mir->trapOnError()) {
@@ -1321,7 +1311,8 @@ void CodeGenerator::visitDivI(LDivI* ins) {
Register rhs = ToRegister(ins->rhs());
Register output = ToRegister(ins->output());
- MOZ_ASSERT_IF(lhs != rhs, rhs != eax);
+ MOZ_ASSERT(lhs == eax);
+ MOZ_ASSERT(rhs != eax);
MOZ_ASSERT(rhs != edx);
MOZ_ASSERT(remainder == edx);
MOZ_ASSERT(output == eax);
@@ -1331,12 +1322,6 @@ void CodeGenerator::visitDivI(LDivI* ins) {
Label done;
OutOfLineCode* ool = nullptr;
- // Put the lhs in eax, for either the negative overflow case or the regular
- // divide case.
- if (lhs != eax) {
- masm.mov(lhs, eax);
- }
-
// Handle divide by zero.
if (mir->canBeDivideByZero()) {
if (mir->trapOnError()) {
@@ -1376,9 +1361,6 @@ void CodeGenerator::visitDivI(LDivI* ins) {
}
// Sign extend the lhs into edx to make (edx:eax), since idiv is 64-bit.
- if (lhs != eax) {
- masm.mov(lhs, eax);
- }
masm.cdq();
masm.idiv(rhs);
@@ -1469,7 +1451,8 @@ void CodeGenerator::visitModI(LModI* ins) {
Register rhs = ToRegister(ins->rhs());
// Required to use idiv.
- MOZ_ASSERT_IF(lhs != rhs, rhs != eax);
+ MOZ_ASSERT(lhs == eax);
+ MOZ_ASSERT(rhs != eax);
MOZ_ASSERT(rhs != edx);
MOZ_ASSERT(remainder == edx);
MOZ_ASSERT(ToRegister(ins->temp0()) == eax);
@@ -1480,11 +1463,6 @@ void CodeGenerator::visitModI(LModI* ins) {
OutOfLineCode* ool = nullptr;
ModOverflowCheck* overflow = nullptr;
- // Set up eax in preparation for doing a div.
- if (lhs != eax) {
- masm.mov(lhs, eax);
- }
-
// Prevent divide by zero.
if (mir->canBeDivideByZero()) {
if (mir->trapOnError()) {
diff --git a/js/src/jit/x86-shared/Lowering-x86-shared.cpp b/js/src/jit/x86-shared/Lowering-x86-shared.cpp
@@ -210,8 +210,8 @@ void LIRGeneratorX86Shared::lowerDivI(MDiv* div) {
return;
}
- LDivI* lir = new (alloc())
- LDivI(useRegister(div->lhs()), useRegister(div->rhs()), tempFixed(edx));
+ auto* lir = new (alloc()) LDivI(useFixedAtStart(div->lhs(), eax),
+ useRegister(div->rhs()), tempFixed(edx));
if (div->fallible()) {
assignSnapshot(lir, div->bailoutKind());
}
@@ -241,8 +241,8 @@ void LIRGeneratorX86Shared::lowerModI(MMod* mod) {
return;
}
- LModI* lir = new (alloc())
- LModI(useRegister(mod->lhs()), useRegister(mod->rhs()), tempFixed(eax));
+ auto* lir = new (alloc()) LModI(useFixedAtStart(mod->lhs(), eax),
+ useRegister(mod->rhs()), tempFixed(eax));
if (mod->fallible()) {
assignSnapshot(lir, mod->bailoutKind());
}
@@ -373,8 +373,8 @@ void LIRGeneratorX86Shared::lowerUDiv(MDiv* div) {
return;
}
- auto* lir = new (alloc())
- LUDiv(useRegister(div->lhs()), useRegister(div->rhs()), tempFixed(edx));
+ auto* lir = new (alloc()) LUDiv(useFixedAtStart(div->lhs(), eax),
+ useRegister(div->rhs()), tempFixed(edx));
if (div->fallible()) {
assignSnapshot(lir, div->bailoutKind());
}
@@ -404,8 +404,8 @@ void LIRGeneratorX86Shared::lowerUMod(MMod* mod) {
return;
}
- auto* lir = new (alloc())
- LUMod(useRegister(mod->lhs()), useRegister(mod->rhs()), tempFixed(eax));
+ auto* lir = new (alloc()) LUMod(useFixedAtStart(mod->lhs(), eax),
+ useRegister(mod->rhs()), tempFixed(eax));
if (mod->fallible()) {
assignSnapshot(lir, mod->bailoutKind());
}
