Increase efficiency of sign_extend_inreg by using subregisters for truncation. As the README suggests sign_extend_subreg is selected to (sext(trunc)).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41010 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 184e355..11b5662 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -157,9 +157,9 @@
   setOperationAction(ISD::SELECT_CC        , MVT::Other, Expand);
   setOperationAction(ISD::MEMMOVE          , MVT::Other, Expand);
   if (Subtarget->is64Bit())
-    setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i32, Expand);
-  setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i16  , Expand);
-  setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i8   , Expand);
+    setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i32, Legal);
+  setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i16  , Legal);
+  setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i8   , Legal);
   setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1   , Expand);
   setOperationAction(ISD::FP_ROUND_INREG   , MVT::f32  , Expand);
   setOperationAction(ISD::FREM             , MVT::f64  , Expand);