tor-browser

commit 437b62f789a51f7521fadbea930851e7b81d2b4c
parent 0bccc18ab3e52a71db292af7f2ed045ffe113bfd
Author: André Bargull <andre.bargull@gmail.com>
Date:   Fri, 24 Oct 2025 14:58:57 +0000

Bug 1996090 - Part 2: Use at-start allocations for LUDivOrMod on riscv64. r=spidermonkey-reviewers,jandem

Differential Revision: https://phabricator.services.mozilla.com/D269849

Diffstat:
M
js/src/jit/riscv64/CodeGenerator-riscv64.cpp
 | 
22
++++++++++++++++------
M
js/src/jit/riscv64/Lowering-riscv64.cpp
 | 
25
++++++++++++++-----------

2 files changed, 30 insertions(+), 17 deletions(-)
diff --git a/js/src/jit/riscv64/CodeGenerator-riscv64.cpp b/js/src/jit/riscv64/CodeGenerator-riscv64.cpp
@@ -2076,15 +2076,25 @@ void CodeGenerator::visitUDivOrMod(LUDivOrMod* ins) {
     }
   }
 
-  masm.ma_modu32(output, lhs, rhs);
-
   // If the remainder is > 0, bailout since this must be a double.
   if (ins->mir()->isDiv()) {
-    if (!ins->mir()->toDiv()->canTruncateRemainder()) {
-      bailoutCmp32(Assembler::NonZero, output, output, ins->snapshot());
+    if (ins->mir()->toDiv()->canTruncateRemainder()) {
+      masm.ma_divu32(output, lhs, rhs);
+    } else {
+      MOZ_ASSERT(lhs != output && rhs != output);
+
+      UseScratchRegisterScope temps(&masm);
+      Register scratch = temps.Acquire();
+
+      // The recommended code sequence to obtain both the quotient and remainder
+      // is div[u] followed by mod[u].
+      masm.ma_divu32(output, lhs, rhs);
+      masm.ma_modu32(scratch, lhs, rhs);
+
+      bailoutCmp32(Assembler::NonZero, scratch, scratch, ins->snapshot());
     }
-    // Get quotient
-    masm.ma_divu32(output, lhs, rhs);
+  } else {
+    masm.ma_modu32(output, lhs, rhs);
   }
 
   if (!ins->mir()->isTruncated()) {
diff --git a/js/src/jit/riscv64/Lowering-riscv64.cpp b/js/src/jit/riscv64/Lowering-riscv64.cpp
@@ -271,12 +271,18 @@ void LIRGeneratorRiscv64::lowerModI64(MMod* mod) {
 }
 
 void LIRGeneratorRiscv64::lowerUDiv(MDiv* div) {
-  MDefinition* lhs = div->getOperand(0);
-  MDefinition* rhs = div->getOperand(1);
+  LAllocation lhs, rhs;
+  if (!div->canTruncateRemainder()) {
+    lhs = useRegister(div->lhs());
+    rhs = useRegister(div->rhs());
+  } else {
+    lhs = useRegisterAtStart(div->lhs());
+    rhs = useRegisterAtStart(div->rhs());
+  }
 
-  LUDivOrMod* lir = new (alloc()) LUDivOrMod;
-  lir->setOperand(0, useRegister(lhs));
-  lir->setOperand(1, useRegister(rhs));
+  auto* lir = new (alloc()) LUDivOrMod;
+  lir->setOperand(0, lhs);
+  lir->setOperand(1, rhs);
   if (div->fallible()) {
     assignSnapshot(lir, div->bailoutKind());
   }
@@ -291,12 +297,9 @@ void LIRGeneratorRiscv64::lowerUDivI64(MDiv* div) {
 }
 
 void LIRGeneratorRiscv64::lowerUMod(MMod* mod) {
-  MDefinition* lhs = mod->getOperand(0);
-  MDefinition* rhs = mod->getOperand(1);
-
-  LUDivOrMod* lir = new (alloc()) LUDivOrMod;
-  lir->setOperand(0, useRegister(lhs));
-  lir->setOperand(1, useRegister(rhs));
+  auto* lir = new (alloc()) LUDivOrMod;
+  lir->setOperand(0, useRegisterAtStart(mod->lhs()));
+  lir->setOperand(1, useRegisterAtStart(mod->rhs()));
   if (mod->fallible()) {
     assignSnapshot(lir, mod->bailoutKind());
   }