tor-browser

commit 0fdd4ee10cf23a943043fe788f9c909a3f6e5811
parent 9aa3304e2fa4134ff8306ee1a69a6f1b00cc3bc7
Author: André Bargull <andre.bargull@gmail.com>
Date:   Thu, 23 Oct 2025 09:56:07 +0000

Bug 1995489: Use 64-bit multiplication for ma_mul32TestOverflow. r=spidermonkey-reviewers,iain

- GCC and Clang both use 64-bit multiplication for `__builtin_mul_overflow` on loong64.
- On mips64, GCC uses 64-bit multiplication, whereas Clang uses `mult` + `mul` (mips64r2)
  resp. `mul` + `muh` (mips64r6). Let's use the GCC approach for consistency with loong64
  and riscv64.

Differential Revision: https://phabricator.services.mozilla.com/D269355

Diffstat:
M
js/src/jit/loong64/MacroAssembler-loong64.cpp
 | 
16
++++++----------
M
js/src/jit/mips-shared/MacroAssembler-mips-shared.cpp
 | 
30
+++++++++++++++++-------------
M
js/src/jit/riscv64/MacroAssembler-riscv64.cpp
 | 
7
+++----

3 files changed, 26 insertions(+), 27 deletions(-)
diff --git a/js/src/jit/loong64/MacroAssembler-loong64.cpp b/js/src/jit/loong64/MacroAssembler-loong64.cpp
@@ -1621,23 +1621,19 @@ void MacroAssemblerLOONG64::ma_mul32TestOverflow(Register rd, Register rj,
                                                  Register rk, Label* overflow) {
   UseScratchRegisterScope temps(asMasm());
   Register scratch = temps.Acquire();
-  Register scratch2 = temps.Acquire();
-  as_mulh_w(scratch, rj, rk);
-  as_mul_w(rd, rj, rk);
-  as_srai_w(scratch2, rd, 31);
-  ma_b(scratch, Register(scratch2), overflow, Assembler::NotEqual);
+  as_mul_d(rd, rj, rk);
+  as_slli_w(scratch, rd, 0);
+  ma_b(rd, scratch, overflow, Assembler::NotEqual);
 }
 
 void MacroAssemblerLOONG64::ma_mul32TestOverflow(Register rd, Register rj,
                                                  Imm32 imm, Label* overflow) {
   UseScratchRegisterScope temps(asMasm());
   Register scratch = temps.Acquire();
-  Register scratch2 = temps.Acquire();
   ma_li(scratch, imm);
-  as_mulh_w(scratch2, rj, scratch);
-  as_mul_w(rd, rj, scratch);
-  as_srai_w(scratch, rd, 31);
-  ma_b(scratch, Register(scratch2), overflow, Assembler::NotEqual);
+  as_mul_d(rd, rj, scratch);
+  as_slli_w(scratch, rd, 0);
+  ma_b(rd, scratch, overflow, Assembler::NotEqual);
 }
 
 void MacroAssemblerLOONG64::ma_div_branch_overflow(Register rd, Register rj,
diff --git a/js/src/jit/mips-shared/MacroAssembler-mips-shared.cpp b/js/src/jit/mips-shared/MacroAssembler-mips-shared.cpp
@@ -357,29 +357,33 @@ void MacroAssemblerMIPSShared::ma_mul32TestOverflow(Register rd, Register rs,
                                                     Register rt,
                                                     Label* overflow) {
   UseScratchRegisterScope temps(*this);
-  Register scratch2 = temps.Acquire();
   Register scratch = temps.Acquire();
+
 #ifdef MIPSR6
-  if (rd == rs) {
-    ma_move(scratch2, rs);
-    rs = scratch2;
-  }
-  as_mul(rd, rs, rt);
-  as_muh(scratch2, rs, rt);
+  as_dmul(rd, rs, rt);
 #else
-  as_mult(rs, rt);
+  as_dmult(rs, rt);
   as_mflo(rd);
-  as_mfhi(scratch2);
 #endif
-  as_sra(scratch, rd, 31);
-  ma_b(scratch, scratch2, overflow, Assembler::NotEqual);
+  ma_sll(scratch, rd, Imm32(0));
+  ma_b(rd, scratch, overflow, Assembler::NotEqual);
 }
 
 void MacroAssemblerMIPSShared::ma_mul32TestOverflow(Register rd, Register rs,
                                                     Imm32 imm,
                                                     Label* overflow) {
-  ma_li(rd, imm);
-  ma_mul32TestOverflow(rd, rs, rd, overflow);
+  UseScratchRegisterScope temps(*this);
+  Register scratch = temps.Acquire();
+
+  ma_li(scratch, imm);
+#ifdef MIPSR6
+  as_dmul(rd, rs, scratch);
+#else
+  as_dmult(rs, scratch);
+  as_mflo(rd);
+#endif
+  ma_sll(scratch, rd, Imm32(0));
+  ma_b(rd, scratch, overflow, Assembler::NotEqual);
 }
 
 void MacroAssemblerMIPSShared::ma_div_branch_overflow(Register rd, Register rs,
diff --git a/js/src/jit/riscv64/MacroAssembler-riscv64.cpp b/js/src/jit/riscv64/MacroAssembler-riscv64.cpp
@@ -4762,12 +4762,11 @@ void MacroAssemblerRiscv64::ma_mul32TestOverflow(Register rd, Register rj,
                                                  Imm32 imm, Label* overflow) {
   UseScratchRegisterScope temps(this);
   Register scratch = temps.Acquire();
-  Register scratch2 = temps.Acquire();
-  MOZ_ASSERT(rd != scratch && rj != scratch2);
+  MOZ_ASSERT(rd != scratch && rj != scratch);
 
-  ma_li(scratch2, imm);
+  ma_li(scratch, imm);
 
-  mul(rd, rj, scratch2);
+  mul(rd, rj, scratch);
   sext_w(scratch, rd);
   ma_b(scratch, rd, overflow, Assembler::NotEqual);
 }