Fixing MathPowHalf on x64.

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 2834 matching lines @@
   XMMRegister input_reg = ToDoubleRegister(instr->InputAt(0));
   ASSERT(ToDoubleRegister(instr->result()).is(input_reg));
   __ sqrtsd(input_reg, input_reg);
 }
 
 
 void LCodeGen::DoMathPowHalf(LUnaryMathOperation* instr) {
   XMMRegister xmm_scratch = xmm0;
   XMMRegister input_reg = ToDoubleRegister(instr->InputAt(0));
   ASSERT(ToDoubleRegister(instr->result()).is(input_reg));
+
+  // Note that according to ECMA-262 15.8.2.13:
+  // Math.pow(-Infinity, 0.5) == Infinity
+  // Math.sqrt(-Infinity) == NaN
+  Label done, sqrt;
+  // Check base for -Infinity.  According to IEEE-754, single-precision

[ulan, 2011/12/05 16:32:41]

double-precision

+  // -Infinity has the highest 12 bits set and the lowest 52 bits cleared.
+  __ movq(kScratchRegister, V8_INT64_C(0xFFF0000000000000), RelocInfo::NONE);
+  __ movq(xmm_scratch, kScratchRegister);
+  __ ucomisd(xmm_scratch, input_reg);
+  __ j(not_equal, &sqrt, Label::kNear);
+  // If input is -Infinity, return Infinity.
+  __ xorps(input_reg, input_reg);
+  __ subsd(input_reg, xmm_scratch);
+  __ jmp(&done, Label::kNear);
+
+  // Square root.
+  __ bind(&sqrt);
   __ xorps(xmm_scratch, xmm_scratch);
   __ addsd(input_reg, xmm_scratch);  // Convert -0 to +0.
   __ sqrtsd(input_reg, input_reg);
+  __ bind(&done);
 }
 
 
 void LCodeGen::DoPower(LPower* instr) {
   LOperand* left = instr->InputAt(0);
   XMMRegister left_reg = ToDoubleRegister(left);
   ASSERT(!left_reg.is(xmm1));
   LOperand* right = instr->InputAt(1);
   XMMRegister result_reg = ToDoubleRegister(instr->result());
   Representation exponent_type = instr->hydrogen()->right()->representation();
@@ skipping 1456 matching lines @@
   RegisterEnvironmentForDeoptimization(environment, Safepoint::kNoLazyDeopt);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64