tor-browser

commit 8839e907e3147d1e22bcd69001f9ee768fc84ed5
parent 113d24b27ae7e2932e195beb80c0a0d261325a22
Author: Rong "Mantle" Bao <webmaster@csmantle.top>
Date:   Thu, 18 Dec 2025 20:33:55 +0000

Bug 2005120 - [riscv64] Part 1: Simplify MacroAssemblerRiscv64Compat::ZeroExtendWord with zext.w from Zba extension. r=m_kato,spidermonkey-reviewers,iain

Differential Revision: https://phabricator.services.mozilla.com/D276403

Diffstat:
M
js/src/jit/riscv64/Assembler-riscv64.cpp
 | 
7
+++++++
M
js/src/jit/riscv64/Assembler-riscv64.h
 | 
5
+++++
M
js/src/jit/riscv64/MacroAssembler-riscv64.h
 | 
4
++++

3 files changed, 16 insertions(+), 0 deletions(-)
diff --git a/js/src/jit/riscv64/Assembler-riscv64.cpp b/js/src/jit/riscv64/Assembler-riscv64.cpp
@@ -67,11 +67,18 @@ void RVFlags::Init() {
     __has_include(<asm/hwprobe.h>)
   riscv_hwprobe probe[1] = {{RISCV_HWPROBE_KEY_IMA_EXT_0, 0}};
   if (syscall(__NR_riscv_hwprobe, probe, 1, 0, nullptr, 0) == 0) {
+    if (probe[0].value & RISCV_HWPROBE_EXT_ZBA) {
+      sZbaExtension = true;
+    }
     if (probe[0].value & RISCV_HWPROBE_EXT_ZBB) {
       sZbbExtension = true;
     }
   }
 #else
+  if (getenv("RISCV_EXT_ZBA")) {
+    // Force on Zba extension for testing purposes or on non-linux platforms.
+    sZbaExtension = true;
+  }
   if (getenv("RISCV_EXT_ZBB")) {
     // Force on Zbb extension for testing purposes or on non-linux platforms.
     sZbbExtension = true;
diff --git a/js/src/jit/riscv64/Assembler-riscv64.h b/js/src/jit/riscv64/Assembler-riscv64.h
@@ -79,9 +79,12 @@ class RVFlags final {
 
   static bool FlagsHaveBeenComputed() { return sComputed; }
 
+  static bool HasZbaExtension() { return sZbaExtension; }
+
   static bool HasZbbExtension() { return sZbbExtension; }
 
  private:
+  static inline bool sZbaExtension = false;
   static inline bool sZbbExtension = false;
   static inline bool sComputed = false;
 };
@@ -505,6 +508,8 @@ class Assembler : public AssemblerShared,
     MOZ_CRASH("unexpected mode");
   }
 
+  static bool HasZbaExtension() { return RVFlags::HasZbaExtension(); }
+
   static bool HasZbbExtension() { return RVFlags::HasZbbExtension(); }
 
   void verifyHeapAccessDisassembly(uint32_t begin, uint32_t end,
diff --git a/js/src/jit/riscv64/MacroAssembler-riscv64.h b/js/src/jit/riscv64/MacroAssembler-riscv64.h
@@ -1090,6 +1090,10 @@ class MacroAssemblerRiscv64Compat : public MacroAssemblerRiscv64 {
 
   void SignExtendWord(Register rd, Register rs) { sext_w(rd, rs); }
   void ZeroExtendWord(Register rd, Register rs) {
+    if (HasZbaExtension()) {
+      zextw(rd, rs);
+      return;
+    }
     slli(rd, rs, 32);
     srli(rd, rd, 32);
   }