Fix Math.pow(-0, 0.5) and Math.pow(-0, -0.5). These are not equal to sqrt(-0...

src/x64/codegen-x64.cc

 // Copyright 2010 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 6951 matching lines @@
   // Test for -0.5.
   // Load xmm2 with -0.5.
   __ movl(answer.reg(), Immediate(0xBF000000));
   __ movd(xmm2, answer.reg());
   __ cvtss2sd(xmm2, xmm2);
   // xmm2 now has -0.5.
   __ ucomisd(xmm2, xmm1);
   __ j(not_equal, &not_minus_half);
 
   // Calculates reciprocal of square root.
-  // Note that 1/sqrt(x) = sqrt(1/x))
-  __ divsd(xmm3, xmm0);
+  // sqrtsd returns -0 when input is -0.  ECMA spec requires +0.
+  __ xorpd(xmm1, xmm1);
+  __ addsd(xmm1, xmm0);
+  __ sqrtsd(xmm1, xmm1);
+  __ divsd(xmm3, xmm1);
   __ movsd(xmm1, xmm3);
-  __ sqrtsd(xmm1, xmm1);
   __ jmp(&allocate_return);
 
   // Test for 0.5.
   __ bind(&not_minus_half);
   // Load xmm2 with 0.5.
   // Since xmm3 is 1 and xmm2 is -0.5 this is simply xmm2 + xmm3.
   __ addsd(xmm2, xmm3);
   // xmm2 now has 0.5.
   __ ucomisd(xmm2, xmm1);
   call_runtime.Branch(not_equal);
 
   // Calculates square root.
-  __ movsd(xmm1, xmm0);
+  // sqrtsd returns -0 when input is -0.  ECMA spec requires +0.
+  __ xorpd(xmm1, xmm1);
+  __ addsd(xmm1, xmm0);
   __ sqrtsd(xmm1, xmm1);
 
   JumpTarget done;
   Label failure, success;
   __ bind(&allocate_return);
   // Make a copy of the frame to enable us to handle allocation
   // failure after the JumpTarget jump.
   VirtualFrame* clone = new VirtualFrame(frame());
   __ AllocateHeapNumber(answer.reg(), exponent.reg(), &failure);
   __ movsd(FieldOperand(answer.reg(), HeapNumber::kValueOffset), xmm1);
@@ skipping 1799 matching lines @@
 }
 
 #endif
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64