tor-browser

commit 7a3f53369269d48cb64697322f23e4c9fa00cb4b
parent d7f8a904ac59e2fa627cc799d990f8cbc8f3251d
Author: André Bargull <andre.bargull@gmail.com>
Date:   Fri, 17 Oct 2025 11:25:42 +0000

Bug 1992993 - Part 5: Avoid running out of registers in branchWithCode. r=spidermonkey-reviewers,iain

Pass an optional scratch register to avoid running out of registers.

This is a regression from bug 1988679.

Differential Revision: https://phabricator.services.mozilla.com/D267793

Diffstat:
M
js/src/jit/mips-shared/MacroAssembler-mips-shared.cpp
 | 
6
++++--
M
js/src/jit/mips64/MacroAssembler-mips64.cpp
 | 
17
++++++++++++++---
M
js/src/jit/mips64/MacroAssembler-mips64.h
 | 
3
++-

3 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/js/src/jit/mips-shared/MacroAssembler-mips-shared.cpp b/js/src/jit/mips-shared/MacroAssembler-mips-shared.cpp
@@ -952,7 +952,8 @@ void MacroAssemblerMIPSShared::ma_b(Register lhs, Register rhs, Label* label,
       UseScratchRegisterScope temps(*this);
       Register scratch = temps.Acquire();
       Condition cond = ma_cmp(scratch, lhs, rhs, c);
-      asMasm().branchWithCode(getBranchCode(scratch, cond), label, jumpKind);
+      asMasm().branchWithCode(getBranchCode(scratch, cond), label, jumpKind,
+                              scratch);
     } break;
   }
 }
@@ -979,7 +980,8 @@ void MacroAssemblerMIPSShared::ma_b(Register lhs, Imm32 imm, Label* label,
         break;
       default:
         Condition cond = ma_cmp(scratch, lhs, imm, c);
-        asMasm().branchWithCode(getBranchCode(scratch, cond), label, jumpKind);
+        asMasm().branchWithCode(getBranchCode(scratch, cond), label, jumpKind,
+                                scratch);
     }
   }
 }
diff --git a/js/src/jit/mips64/MacroAssembler-mips64.cpp b/js/src/jit/mips64/MacroAssembler-mips64.cpp
@@ -1050,7 +1050,8 @@ void MacroAssemblerMIPS64::ma_bal(Label* label, DelaySlotFill delaySlotFill) {
 }
 
 void MacroAssemblerMIPS64::branchWithCode(InstImm code, Label* label,
-                                          JumpKind jumpKind) {
+                                          JumpKind jumpKind,
+                                          Register branchCodeScratch) {
   // simply output the pointer of one label as its id,
   // notice that after one label destructor, the pointer will be reused.
   spew("branch .Llabel %p", label);
@@ -1080,7 +1081,12 @@ void MacroAssemblerMIPS64::branchWithCode(InstImm code, Label* label,
       UseScratchRegisterScope temps(*this);
       // Handle long jump
       addLongJump(nextOffset(), BufferOffset(label->offset()));
-      Register scratch = temps.Acquire();
+      Register scratch = branchCodeScratch;
+      if (scratch == InvalidReg) {
+        // Request a new scratch register if |branchCodeScratch| is invalid.
+        // NB: |branchCodeScratch| must not be used before encoding |code|.
+        scratch = temps.Acquire();
+      }
       ma_liPatchable(scratch, ImmWord(LabelBase::INVALID_OFFSET));
       as_jr(scratch);
       as_nop();
@@ -1098,7 +1104,12 @@ void MacroAssemblerMIPS64::branchWithCode(InstImm code, Label* label,
     UseScratchRegisterScope temps(*this);
     // No need for a "nop" here because we can clobber scratch.
     addLongJump(nextOffset(), BufferOffset(label->offset()));
-    Register scratch = temps.Acquire();
+    Register scratch = branchCodeScratch;
+    if (scratch == InvalidReg) {
+      // Request a new scratch register if |branchCodeScratch| is invalid.
+      // NB: |branchCodeScratch| must not be used before encoding |code|.
+      scratch = temps.Acquire();
+    }
     ma_liPatchable(scratch, ImmWord(LabelBase::INVALID_OFFSET));
     as_jr(scratch);
     as_nop();
diff --git a/js/src/jit/mips64/MacroAssembler-mips64.h b/js/src/jit/mips64/MacroAssembler-mips64.h
@@ -193,7 +193,8 @@ class MacroAssemblerMIPS64 : public MacroAssemblerMIPSShared {
   void ma_pop(Register r);
   void ma_push(Register r);
 
-  void branchWithCode(InstImm code, Label* label, JumpKind jumpKind);
+  void branchWithCode(InstImm code, Label* label, JumpKind jumpKind,
+                      Register branchCodeScratch = InvalidReg);
   // branches when done from within mips-specific code
   void ma_b(Register lhs, ImmWord imm, Label* l, Condition c,
             JumpKind jumpKind = LongJump);