Avoid wrong imul deopt on ia32 and x64 (fixes v8 bug 2339).

src/x64/lithium-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1105 matching lines @@
   }
 
   if (can_overflow) {
     DeoptimizeIf(overflow, instr->environment());
   }
 
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     // Bail out if the result is supposed to be negative zero.
     Label done;
     __ testl(left, left);
     __ j(not_zero, &done, Label::kNear);

[Vyacheslav Egorov (Google), 2012/09/26 10:07:36]

This code is redundant if right is 0. (left is always zero).

     if (right->IsConstantOperand()) {
-      if (ToInteger32(LConstantOperand::cast(right)) <= 0) {
+      if (ToInteger32(LConstantOperand::cast(right)) < 0) {
         DeoptimizeIf(no_condition, instr->environment());
+      } else if (ToInteger32(LConstantOperand::cast(right)) == 0) {
+        __ cmpl(kScratchRegister, Immediate(0));
+        DeoptimizeIf(less, instr->environment());
       }
     } else if (right->IsStackSlot()) {
       __ orl(kScratchRegister, ToOperand(right));
       DeoptimizeIf(sign, instr->environment());
     } else {
       // Test the non-zero operand for negative sign.
       __ orl(kScratchRegister, ToRegister(right));
       DeoptimizeIf(sign, instr->environment());
     }
     __ bind(&done);
@@ skipping 4179 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64