MIPS: Fixed Hydrogen environment handling for mul-i ARM and ARM64.

src/mips64/lithium-mips64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sstream>
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_MIPS64
 
@@ skipping 1483 matching lines @@
   if (instr->representation().IsSmiOrInteger32()) {
     DCHECK(instr->left()->representation().Equals(instr->representation()));
     DCHECK(instr->right()->representation().Equals(instr->representation()));
     HValue* left = instr->BetterLeftOperand();
     HValue* right = instr->BetterRightOperand();
     LOperand* left_op;
     LOperand* right_op;
     bool can_overflow = instr->CheckFlag(HValue::kCanOverflow);
     bool bailout_on_minus_zero = instr->CheckFlag(HValue::kBailoutOnMinusZero);
 
+    int32_t constant_value = 0;
     if (right->IsConstant()) {
       HConstant* constant = HConstant::cast(right);
-      int32_t constant_value = constant->Integer32Value();
+      constant_value = constant->Integer32Value();
       // Constants -1, 0 and 1 can be optimized if the result can overflow.
       // For other constants, it can be optimized only without overflow.
       if (!can_overflow || ((constant_value >= -1) && (constant_value <= 1))) {
         left_op = UseRegisterAtStart(left);
         right_op = UseConstant(right);
       } else {
         if (bailout_on_minus_zero) {
           left_op = UseRegister(left);
         } else {
           left_op = UseRegisterAtStart(left);
         }
         right_op = UseRegister(right);
       }
     } else {
       if (bailout_on_minus_zero) {
         left_op = UseRegister(left);
       } else {
         left_op = UseRegisterAtStart(left);
       }
       right_op = UseRegister(right);
     }
     LMulI* mul = new(zone()) LMulI(left_op, right_op);
-    if (can_overflow || bailout_on_minus_zero) {
+    if (right_op->IsConstantOperand()
+            ? ((can_overflow && constant_value == -1) ||
+               (bailout_on_minus_zero && constant_value <= 0))
+            : (can_overflow || bailout_on_minus_zero)) {
       AssignEnvironment(mul);
     }
     return DefineAsRegister(mul);
 
   } else if (instr->representation().IsDouble()) {
     if (kArchVariant == kMips64r2) {
       if (instr->HasOneUse() && instr->uses().value()->IsAdd()) {
         HAdd* add = HAdd::cast(instr->uses().value());
         if (instr == add->left()) {
           // This mul is the lhs of an add. The add and mul will be folded
@@ skipping 1057 matching lines @@
   LOperand* function = UseRegisterAtStart(instr->function());
   LAllocateBlockContext* result =
       new(zone()) LAllocateBlockContext(context, function);
   return MarkAsCall(DefineFixed(result, cp), instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS64