Subzero: Use cvttss2si and similar instead of cvtss2si for fp->int casts.

src/IceTargetLoweringX8632.h

Index: src/IceTargetLoweringX8632.h
diff --git a/src/IceTargetLoweringX8632.h b/src/IceTargetLoweringX8632.h
index 6f8ee02f96cf4023896a053cf4e5d3530db83e5e..251baa205cd661b46db01ae802128aa621428939 100644
--- a/src/IceTargetLoweringX8632.h
+++ b/src/IceTargetLoweringX8632.h
@@ -264,7 +264,12 @@ protected:
     Context.insert(InstFakeDef::create(Func, Eax));
   }
   void _cvt(Variable *Dest, Operand *Src0) {
-    Context.insert(InstX8632Cvt::create(Func, Dest, Src0));
+    const bool Trunc = false;
+    Context.insert(InstX8632Cvt::create(Func, Dest, Src0, Trunc));
+  }
+  void _cvtt(Variable *Dest, Operand *Src0) {
+    const bool Trunc = true;
+    Context.insert(InstX8632Cvt::create(Func, Dest, Src0, Trunc));
   }
   void _div(Variable *Dest, Operand *Src0, Operand *Src1) {
     Context.insert(InstX8632Div::create(Func, Dest, Src0, Src1));