tor-browser

commit 3f463ccfc6938fdd5fcaaede6608feb4e2c0ff0d
parent 089a74ef4ada8f1289878ff3caf21be428bd3a82
Author: André Bargull <andre.bargull@gmail.com>
Date:   Wed, 22 Oct 2025 15:31:21 +0000

Bug 1995704 - Part 1: Improve register allocation for LPowHalfD. r=spidermonkey-reviewers,jandem

- `defineReuseInput` isn't needed for arm32, loong64, mips64, and riscv64.
- `useRegisterAtStart` can be used for arm64.

And use `Fneg` for ARM64 to save one instruction.

Differential Revision: https://phabricator.services.mozilla.com/D269548

Diffstat:
M
js/src/jit/arm/Lowering-arm.cpp
 | 
2
+-
M
js/src/jit/arm64/CodeGenerator-arm64.cpp
 | 
3
+--
M
js/src/jit/arm64/Lowering-arm64.cpp
 | 
2
+-
M
js/src/jit/loong64/Lowering-loong64.cpp
 | 
2
+-
M
js/src/jit/mips-shared/Lowering-mips-shared.cpp
 | 
2
+-
M
js/src/jit/riscv64/Lowering-riscv64.cpp
 | 
2
+-

6 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/js/src/jit/arm/Lowering-arm.cpp b/js/src/jit/arm/Lowering-arm.cpp
@@ -500,7 +500,7 @@ void LIRGenerator::visitPowHalf(MPowHalf* ins) {
   MDefinition* input = ins->input();
   MOZ_ASSERT(input->type() == MIRType::Double);
   LPowHalfD* lir = new (alloc()) LPowHalfD(useRegisterAtStart(input));
-  defineReuseInput(lir, ins, 0);
+  define(lir, ins);
 }
 
 void LIRGeneratorARM::lowerWasmSelectI(MWasmSelect* select) {
diff --git a/js/src/jit/arm64/CodeGenerator-arm64.cpp b/js/src/jit/arm64/CodeGenerator-arm64.cpp
@@ -1005,8 +1005,7 @@ void CodeGenerator::visitPowHalfD(LPowHalfD* ins) {
     masm.branchDouble(cond, input, scratch, &sqrt);
 
     // Math.pow(-Infinity, 0.5) == Infinity.
-    masm.zeroDouble(output);
-    masm.subDouble(scratch, output);
+    masm.Fneg(ARMFPRegister(output, 64), ARMFPRegister(scratch, 64));
     masm.jump(&done);
 
     masm.bind(&sqrt);
diff --git a/js/src/jit/arm64/Lowering-arm64.cpp b/js/src/jit/arm64/Lowering-arm64.cpp
@@ -363,7 +363,7 @@ void LIRGeneratorARM64::lowerWasmBuiltinModI64(MWasmBuiltinModI64* mod) {
 void LIRGenerator::visitPowHalf(MPowHalf* ins) {
   MDefinition* input = ins->input();
   MOZ_ASSERT(input->type() == MIRType::Double);
-  LPowHalfD* lir = new (alloc()) LPowHalfD(useRegister(input));
+  LPowHalfD* lir = new (alloc()) LPowHalfD(useRegisterAtStart(input));
   define(lir, ins);
 }
 
diff --git a/js/src/jit/loong64/Lowering-loong64.cpp b/js/src/jit/loong64/Lowering-loong64.cpp
@@ -561,7 +561,7 @@ void LIRGenerator::visitPowHalf(MPowHalf* ins) {
   MDefinition* input = ins->input();
   MOZ_ASSERT(input->type() == MIRType::Double);
   LPowHalfD* lir = new (alloc()) LPowHalfD(useRegisterAtStart(input));
-  defineReuseInput(lir, ins, 0);
+  define(lir, ins);
 }
 
 void LIRGenerator::visitExtendInt32ToInt64(MExtendInt32ToInt64* ins) {
diff --git a/js/src/jit/mips-shared/Lowering-mips-shared.cpp b/js/src/jit/mips-shared/Lowering-mips-shared.cpp
@@ -269,7 +269,7 @@ void LIRGenerator::visitPowHalf(MPowHalf* ins) {
   MDefinition* input = ins->input();
   MOZ_ASSERT(input->type() == MIRType::Double);
   LPowHalfD* lir = new (alloc()) LPowHalfD(useRegisterAtStart(input));
-  defineReuseInput(lir, ins, 0);
+  define(lir, ins);
 }
 
 void LIRGeneratorMIPSShared::lowerWasmSelectI(MWasmSelect* select) {
diff --git a/js/src/jit/riscv64/Lowering-riscv64.cpp b/js/src/jit/riscv64/Lowering-riscv64.cpp
@@ -561,7 +561,7 @@ void LIRGenerator::visitPowHalf(MPowHalf* ins) {
   MDefinition* input = ins->input();
   MOZ_ASSERT(input->type() == MIRType::Double);
   LPowHalfD* lir = new (alloc()) LPowHalfD(useRegisterAtStart(input));
-  defineReuseInput(lir, ins, 0);
+  define(lir, ins);
 }
 
 void LIRGenerator::visitExtendInt32ToInt64(MExtendInt32ToInt64* ins) {