Ensure consistency of Math.sqrt on Intel platforms.

src/ia32/codegen-ia32.cc

Index: src/ia32/codegen-ia32.cc
diff --git a/src/ia32/codegen-ia32.cc b/src/ia32/codegen-ia32.cc
index de6901f9cdbe34d84066b317fd5fb9af5950da80..f717f059bbc10dc36a3fa88f03cf52a2105f2f1f 100644
--- a/src/ia32/codegen-ia32.cc
+++ b/src/ia32/codegen-ia32.cc
@@ -57,8 +57,7 @@ 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,
@@ -99,7 +98,44 @@ 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]

Using !CpuFeatures::IsSupported(SSE2) here would guarantee consistency between
runs with Crankshaft and without it on SSE2 platforms.

+  MacroAssembler masm(NULL, buffer, static_cast<int>(actual_size));
+  // esp[1 * kPointerSize]: raw double input
+  // esp[0 * kPointerSize]: return address
+  // Move double input into registers.
+
+  // Crankshaft cannot be enabled without SSE2.
+  ASSERT(CpuFeatures::IsSupported(SSE2));
+  {
+    CpuFeatures::Scope use_sse2(SSE2);
+    __ movdbl(xmm0, Operand(esp, 1 * kPointerSize));
+    __ sqrtsd(xmm0, xmm0);
+    __ movdbl(Operand(esp, 1 * kPointerSize), xmm0);
+    // Load result into floating point register as return value.
+    __ fld_d(Operand(esp, 1 * kPointerSize));
+    __ 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);
 }