[turbofan] Implemented the TruncateFloat32ToInt64 TurboFan operator.

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 84542b60991f9c9323a6babeb3a74f1ca673358c..af8f8e8aa7b167c56371cee42c79469823ed0a5d 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -1043,6 +1043,13 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ AssertZeroExtended(i.OutputRegister());
       break;
     }
+    case kSSEFloat32ToInt64:
+      if (instr->InputAt(0)->IsDoubleRegister()) {
+        __ Cvttss2siq(i.OutputRegister(), i.InputDoubleRegister(0));
+      } else {
+        __ Cvttss2siq(i.OutputRegister(), i.InputOperand(0));
+      }
+      break;
     case kSSEFloat64ToInt64:
       if (instr->InputAt(0)->IsDoubleRegister()) {
         __ Cvttsd2siq(i.OutputRegister(), i.InputDoubleRegister(0));