tor-browser

commit 19d3fc64145c543ce42f73957f532d179660262e
parent 881b2dd3dc1f85f7a5f20cdea442dcb3271d35e0
Author: André Bargull <andre.bargull@gmail.com>
Date:   Tue, 11 Nov 2025 12:29:35 +0000

Bug 1998452: Avoid REX prefix for And with unsigned 32-bit immediate. r=spidermonkey-reviewers,iain

Not emitting the REX prefix saves a byte.

Differential Revision: https://phabricator.services.mozilla.com/D271434

Diffstat:
M
js/src/jit/x64/MacroAssembler-x64-inl.h
 | 
16
+++++++++++++---
M
js/src/jit/x64/MacroAssembler-x64.cpp
 | 
4
++--

2 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/js/src/jit/x64/MacroAssembler-x64-inl.h b/js/src/jit/x64/MacroAssembler-x64-inl.h
@@ -84,18 +84,28 @@ void MacroAssembler::notPtr(Register reg) { notq(reg); }
 
 void MacroAssembler::andPtr(Register src, Register dest) { andq(src, dest); }
 
-void MacroAssembler::andPtr(Imm32 imm, Register dest) { andq(imm, dest); }
+void MacroAssembler::andPtr(Imm32 imm, Register dest) {
+  if (imm.value >= 0) {
+    andl(imm, dest);
+  } else {
+    andq(imm, dest);
+  }
+}
 
 void MacroAssembler::andPtr(Imm32 imm, Register src, Register dest) {
   if (src != dest) {
     movq(src, dest);
   }
-  andq(imm, dest);
+  andPtr(imm, dest);
 }
 
 void MacroAssembler::and64(Imm64 imm, Register64 dest) {
   if (INT32_MIN <= int64_t(imm.value) && int64_t(imm.value) <= INT32_MAX) {
-    andq(Imm32(imm.value), dest.reg);
+    if (int32_t(imm.value) >= 0) {
+      andl(Imm32(imm.value), dest.reg);
+    } else {
+      andq(Imm32(imm.value), dest.reg);
+    }
   } else {
     ScratchRegisterScope scratch(*this);
     movq(ImmWord(uintptr_t(imm.value)), scratch);
diff --git a/js/src/jit/x64/MacroAssembler-x64.cpp b/js/src/jit/x64/MacroAssembler-x64.cpp
@@ -1578,7 +1578,7 @@ void MacroAssembler::convertUInt64ToDouble(Register64 input,
   mov(input.reg, scratch);
   mov(input.reg, temp);
   shrq(Imm32(1), scratch);
-  andq(Imm32(1), temp);
+  andl(Imm32(1), temp);
   orq(temp, scratch);
 
   vcvtsq2sd(scratch, output, output);
@@ -1608,7 +1608,7 @@ void MacroAssembler::convertUInt64ToFloat32(Register64 input,
   mov(input.reg, scratch);
   mov(input.reg, temp);
   shrq(Imm32(1), scratch);
-  andq(Imm32(1), temp);
+  andl(Imm32(1), temp);
   orq(temp, scratch);
 
   vcvtsq2ss(scratch, output, output);