Merge revision 6500-6600 from bleeding_edge to the isolates branch.

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
===================================================================
--- src/x64/codegen-x64.cc	(revision 7030)
+++ src/x64/codegen-x64.cc	(working copy)
@@ -6970,10 +6970,12 @@
   __ 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.
@@ -6986,7 +6988,9 @@
   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;