Refactor Math.min/max to be a single HInstruction.

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 8dd58a2ae6d26efcfa8245a3da6320b3cb5bacb3..6552904f3cd9839f9e091d509253a83ed83673b5 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1393,6 +1393,67 @@ void LCodeGen::DoAddI(LAddI* instr) {
 }
 
 
+void LCodeGen::DoMathMinMax(LMathMinMax* instr) {
+  LOperand* left = instr->InputAt(0);
+  LOperand* right = instr->InputAt(1);
+  ASSERT(left->Equals(instr->result()));
+  HMathMinMax::Operation operation = instr->hydrogen()->operation();
+  if (instr->hydrogen()->representation().IsInteger32()) {
+    Label return_left;
+    Condition condition = (operation == HMathMinMax::kMathMin)
+        ? less_equal
+        : greater_equal;
+    Register left_reg = ToRegister(left);
+    if (right->IsConstantOperand()) {
+      Immediate right_imm =
+          Immediate(ToInteger32(LConstantOperand::cast(right)));
+      __ cmpq(left_reg, right_imm);
+      __ j(condition, &return_left, Label::kNear);
+      __ movq(left_reg, right_imm);
+    } else {
+      Operand right_op = ToOperand(right);
+      __ cmpq(left_reg, right_op);
+      __ j(condition, &return_left, Label::kNear);
+      __ movq(left_reg, right_op);
+    }
+    __ bind(&return_left);
+  } else {
+    ASSERT(instr->hydrogen()->representation().IsDouble());
+    Label check_nan_left, check_zero, return_left, return_right;
+    Condition condition = (operation == HMathMinMax::kMathMin) ? below : above;
+    XMMRegister left_reg = ToDoubleRegister(left);
+    XMMRegister right_reg = ToDoubleRegister(right);
+    __ ucomisd(left_reg, right_reg);
+    __ j(parity_even, &check_nan_left, Label::kNear);  // At least one NaN.
+    __ j(equal, &check_zero, Label::kNear);  // left == right.
+    __ j(condition, &return_left, Label::kNear);
+    __ jmp(&return_right, Label::kNear);
+
+    __ bind(&check_zero);
+    XMMRegister xmm_scratch = xmm0;
+    __ xorps(xmm_scratch, xmm_scratch);
+    __ ucomisd(left_reg, xmm_scratch);
+    __ j(not_equal, &return_left, Label::kNear);  // left == right != 0.
+    // At this point, both left and right are either 0 or -0.
+    if (operation == HMathMinMax::kMathMin) {
+      __ orpd(left_reg, right_reg);
+    } else {
+      // Since we operate on +0 and/or -0, addsd and andsd have the same effect.
+      __ addsd(left_reg, right_reg);
+    }
+    __ jmp(&return_left, Label::kNear);
+
+    __ bind(&check_nan_left);
+    __ ucomisd(left_reg, left_reg);  // NaN check.
+    __ j(parity_even, &return_left, Label::kNear);
+    __ bind(&return_right);
+    __ movsd(left_reg, right_reg);
+
+    __ bind(&return_left);
+  }
+}
+
+
 void LCodeGen::DoArithmeticD(LArithmeticD* instr) {
   XMMRegister left = ToDoubleRegister(instr->InputAt(0));
   XMMRegister right = ToDoubleRegister(instr->InputAt(1));