Ensure consistency of Math.sqrt on Intel platforms.

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index 902f7e93a31536c04938ef2fcfdea749cb67f6d4..4b9217cec7f0026ae7fbeb00b0e5101a86e570ae 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -55,8 +55,7 @@ void StubRuntimeCallHelper::AfterCall(MacroAssembler* masm) const {
 #define __ masm.
 
 
-TranscendentalFunction CreateTranscendentalFunction(
-    TranscendentalCache::Type type) {
+UnaryMathFunction CreateTranscendentalFunction(TranscendentalCache::Type type) {
   size_t actual_size;
   // Allocate buffer in executable space.
   byte* buffer = static_cast<byte*>(OS::Allocate(1 * KB,
@@ -96,7 +95,34 @@ TranscendentalFunction CreateTranscendentalFunction(
 
   CPU::FlushICache(buffer, actual_size);
   OS::ProtectCode(buffer, actual_size);
-  return FUNCTION_CAST<TranscendentalFunction>(buffer);
+  return FUNCTION_CAST<UnaryMathFunction>(buffer);
+}
+
+
+UnaryMathFunction CreateSqrtFunction() {
+  size_t actual_size;
+  // Allocate buffer in executable space.
+  byte* buffer = static_cast<byte*>(OS::Allocate(1 * KB,
+                                                 &actual_size,
+                                                 true));
+
+  // If crankshaft is disabled, we can use libc's implementation to ensure
+  // consistency since fullcodegen's implementation always calls into runtime.
+  if (buffer == NULL || !V8::UseCrankshaft()) return &sqrt;

[Sven Panne, 2012/03/12 13:23:46]

To guarantee consistency between runs with and without "--nouse-crankshaft", it
would be better to remove this check. x64 always has SSE.

+
+  MacroAssembler masm(NULL, buffer, static_cast<int>(actual_size));
+  // xmm0: raw double input.
+  // Move double input into registers.
+  __ sqrtsd(xmm0, xmm0);
+  __ Ret();
+
+  CodeDesc desc;
+  masm.GetCode(&desc);
+  ASSERT(desc.reloc_size == 0);
+
+  CPU::FlushICache(buffer, actual_size);
+  OS::ProtectCode(buffer, actual_size);
+  return FUNCTION_CAST<UnaryMathFunction>(buffer);
 }