[x64] Use vcvtlsi2sd when AVX is enabled

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index ad3827aba572e60eff81d0e83357704bd6bee525..461e097cd67c0131531d9945ba0dd06b530b5a8a 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -788,14 +788,26 @@ void MacroAssembler::PopCallerSaved(SaveFPRegsMode fp_mode,
 
 
 void MacroAssembler::Cvtlsi2sd(XMMRegister dst, Register src) {
-  xorps(dst, dst);
-  cvtlsi2sd(dst, src);
+  if (CpuFeatures::IsSupported(AVX)) {
+    CpuFeatureScope scope(this, AVX);
+    vxorpd(dst, dst, dst);
+    vcvtlsi2sd(dst, dst, src);
+  } else {
+    xorps(dst, dst);

[Benedikt Meurer, 2015/10/15 05:13:47]

Nit: Use xorpd for consistency here?

[alph, 2015/10/15 05:20:07]

Ok.
I didn't want to touch legacy code in this patch.
In general I plan to replace all these xorps'es across entire code. I remember
from my previous compiler experience that mixing float types has some
performance penalties on certain AMD CPUs. 

+    cvtlsi2sd(dst, src);
+  }
 }
 
 
 void MacroAssembler::Cvtlsi2sd(XMMRegister dst, const Operand& src) {
-  xorps(dst, dst);
-  cvtlsi2sd(dst, src);
+  if (CpuFeatures::IsSupported(AVX)) {
+    CpuFeatureScope scope(this, AVX);
+    vxorpd(dst, dst, dst);
+    vcvtlsi2sd(dst, dst, src);
+  } else {
+    xorps(dst, dst);

[Benedikt Meurer, 2015/10/15 05:13:47]

Nit: Use xorpd for consistency here?

+    cvtlsi2sd(dst, src);
+  }
 }