Port CompileMathFloorCall from ia32 to x64

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 8969d89a6a75db3b8a021ea666db81cffb4c9033..e82eca875f2b44dc834aa994e007addac6e2c2b2 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -2992,6 +2992,17 @@ void Assembler::ucomisd(XMMRegister dst, const Operand& src) {
 }
 
 
+void Assembler::cmpltsd(XMMRegister dst, XMMRegister src) {
+  EnsureSpace ensure_space(this);
+  emit(0xF2);
+  emit_optional_rex_32(dst, src);
+  emit(0x0F);
+  emit(0xC2);
+  emit_sse_operand(dst, src);
+  emit(0x01);  // LT == 1
+}
+
+
 void Assembler::roundsd(XMMRegister dst, XMMRegister src,
                         Assembler::RoundingMode mode) {
   ASSERT(IsEnabled(SSE4_1));