[X86] Replace action Promote with Expand for operation ISD::SINT_TO_FP

Summary:
If attribute "use-soft-float"="true" is set then X86ISelLowering.cpp sets
'Promote' action for ISD::SINT_TO_FP operation on type i32.

But 'Promote' action is not proper in this case since lib function
__floatsidf is available for casting from signed int to float type.
Thus Expand action is more suitable here.

The Expand action should be set for ISD::UINT_TO_FP for soft float as well.

If function attribute "use-soft-float"="true" is set then infinite looping
can happen in DAG combining, function visitSINT_TO_FP() replaces SINT_TO_FP
node with UINT_TO_FP node and function combineUIntToFP() replace vice versa in cycle.
The fix prevents it.

Patch by vrybalov

Differential Revision: https://reviews.llvm.org/D45572

llvm-svn: 330711

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9ca25657270..1e6fb923fea 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -216,6 +216,8 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     // We have an algorithm for SSE2, and we turn this into a 64-bit
     // FILD or VCVTUSI2SS/SD for other targets.
     setOperationAction(ISD::UINT_TO_FP     , MVT::i32  , Custom);
+  } else {
+    setOperationAction(ISD::UINT_TO_FP     , MVT::i32  , Expand);
   }
 
   // Promote i1/i8 SINT_TO_FP to larger SINT_TO_FP's, as X86 doesn't have
@@ -235,7 +237,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     }
   } else {
     setOperationAction(ISD::SINT_TO_FP     , MVT::i16  , Promote);
-    setOperationAction(ISD::SINT_TO_FP     , MVT::i32  , Promote);
+    setOperationAction(ISD::SINT_TO_FP     , MVT::i32  , Expand);
   }
 
   // Promote i1/i8 FP_TO_SINT to larger FP_TO_SINTS's, as X86 doesn't have