[turbofan] Add RoundUint32ToFloat32 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 68aba0d371c523cdb0ee68b4a9999efecbceccde..a5b9d17cebc243972888daa34371e89d8e4ffd11 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -1251,6 +1251,14 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       }
       __ Cvtqsi2sd(i.OutputDoubleRegister(), kScratchRegister);
       break;
+    case kSSEUint32ToFloat32:
+      if (instr->InputAt(0)->IsRegister()) {
+        __ movl(kScratchRegister, i.InputRegister(0));
+      } else {
+        __ movl(kScratchRegister, i.InputOperand(0));
+      }
+      __ Cvtqsi2ss(i.OutputDoubleRegister(), kScratchRegister);
+      break;
     case kSSEFloat64ExtractLowWord32:
       if (instr->InputAt(0)->IsDoubleStackSlot()) {
         __ movl(i.OutputRegister(), i.InputOperand(0));