Fix three bugs with handling negative zero in the optimizing compiler.

src/x64/lithium-codegen-x64.cc

 // Copyright 2011 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 2755 matching lines @@
       // Deoptimize if minus zero.
       __ movq(output_reg, input_reg);
       __ subq(output_reg, Immediate(1));
       DeoptimizeIf(overflow, instr->environment());
     }
     __ roundsd(xmm_scratch, input_reg, Assembler::kRoundDown);
     __ cvttsd2si(output_reg, xmm_scratch);
     __ cmpl(output_reg, Immediate(0x80000000));
     DeoptimizeIf(equal, instr->environment());
   } else {
+    // Deoptimize on negative inputs.
     __ xorps(xmm_scratch, xmm_scratch);  // Zero the register.
     __ ucomisd(input_reg, xmm_scratch);
-
+    DeoptimizeIf(below, instr->environment());
     if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
-      DeoptimizeIf(below_equal, instr->environment());
-    } else {
-      DeoptimizeIf(below, instr->environment());
+      // Check for negative zero.
+      __ j(above, &positive_sign, Label::kNear);
+      __ movmskpd(output_reg, input_reg);
+      __ testq(output_reg, Immediate(1));
+      DeoptimizeIf(not_zero, instr->environment());
+      __ Set(output_reg, Immediate(0));
+      __ jmp(&done);
+      __ bind(&positive_sign);
     }
 
     // Use truncating instruction (OK because input is positive).
     __ cvttsd2si(output_reg, input_reg);
 
     // Overflow is signalled with minint.
     __ cmpl(output_reg, Immediate(0x80000000));
     DeoptimizeIf(equal, instr->environment());
   }
+  __ bind(&done);
 }
 
 
 void LCodeGen::DoMathRound(LUnaryMathOperation* instr) {
   const XMMRegister xmm_scratch = xmm0;
   Register output_reg = ToRegister(instr->result());
   XMMRegister input_reg = ToDoubleRegister(instr->InputAt(0));
 
   Label done;
   // xmm_scratch = 0.5
@@ skipping 1382 matching lines @@
   RegisterEnvironmentForDeoptimization(environment);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64