Port r11517 (not deopt Math.floor on negative input) to x64, sse2.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 57db277577ef3d9ca3258731893664add185809b..808c4d87355f3626d5829df45f62745d893f236c 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3031,7 +3031,6 @@ void LCodeGen::DoMathFloor(LUnaryMathOperation* instr) {
   XMMRegister xmm_scratch = xmm0;
   Register output_reg = ToRegister(instr->result());
   XMMRegister input_reg = ToDoubleRegister(instr->InputAt(0));
-  Label done;
 
   if (CpuFeatures::IsSupported(SSE4_1)) {
     CpuFeatures::Scope scope(SSE4_1);
@@ -3046,10 +3045,13 @@ void LCodeGen::DoMathFloor(LUnaryMathOperation* instr) {
     __ cmpl(output_reg, Immediate(0x80000000));
     DeoptimizeIf(equal, instr->environment());
   } else {
+    Label negative_sign, done;
     // Deoptimize on negative inputs.
     __ xorps(xmm_scratch, xmm_scratch);  // Zero the register.
     __ ucomisd(input_reg, xmm_scratch);
-    DeoptimizeIf(below, instr->environment());
+    DeoptimizeIf(parity_even, instr->environment());
+    __ j(below, &negative_sign, Label::kNear);
+
     if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
       // Check for negative zero.
       Label positive_sign;
@@ -3064,12 +3066,23 @@ void LCodeGen::DoMathFloor(LUnaryMathOperation* instr) {
 
     // Use truncating instruction (OK because input is positive).
     __ cvttsd2si(output_reg, input_reg);
-
     // Overflow is signalled with minint.
     __ cmpl(output_reg, Immediate(0x80000000));
     DeoptimizeIf(equal, instr->environment());
+    __ jmp(&done, Label::kNear);
+
+    // Non-zero negative reaches here.
+    __ bind(&negative_sign);
+    // Truncate, then compare and compensate.
+    __ cvttsd2si(output_reg, input_reg);
+    __ cvtlsi2sd(xmm_scratch, output_reg);
+    __ ucomisd(input_reg, xmm_scratch);
+    __ j(equal, &done, Label::kNear);
+    __ subl(output_reg, Immediate(1));
+    DeoptimizeIf(overflow, instr->environment());
+
+    __ bind(&done);
   }
-  __ bind(&done);
 }