[turbofan] Add the RoundInt32ToFloat32 operator to turbofan.

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index be406fbad26d5ee0b59e870d7b66a589660bf865..4154e923836edf46dbb3ab58d5577583f5649c94 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -1197,6 +1197,13 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
         __ Cvtlsi2sd(i.OutputDoubleRegister(), i.InputOperand(0));
       }
       break;
+    case kSSEInt32ToFloat32:
+      if (instr->InputAt(0)->IsRegister()) {
+        __ Cvtlsi2ss(i.OutputDoubleRegister(), i.InputRegister(0));
+      } else {
+        __ Cvtlsi2ss(i.OutputDoubleRegister(), i.InputOperand(0));
+      }
+      break;
     case kSSEInt64ToFloat32:
       if (instr->InputAt(0)->IsRegister()) {
         __ Cvtqsi2ss(i.OutputDoubleRegister(), i.InputRegister(0));