[llvm] r319640 - [X86] Don't turn UINT_TO_FP into SINT_TO_FP during lowering.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Sun Dec  3 21:38:44 2017
New Revision: 319640

URL: http://llvm.org/viewvc/llvm-project?rev=319640&view=rev
Log:
[X86] Don't turn UINT_TO_FP into SINT_TO_FP during lowering.

We already do this as a DAG combine. The version during lowering can only trigger if known bits changes something that improves known bits analysis. But this means we should be improving known bits analysis to work on the unlowered form instead.

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=319640&r1=319639&r2=319640&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Sun Dec  3 21:38:44 2017
@@ -15820,12 +15820,6 @@ SDValue X86TargetLowering::LowerUINT_TO_
   SDLoc dl(Op);
   auto PtrVT = getPointerTy(DAG.getDataLayout());
 
-  // Since UINT_TO_FP is legal (it's marked custom), dag combiner won't
-  // optimize it to a SINT_TO_FP when the sign bit is known zero. Perform
-  // the optimization here.
-  if (DAG.SignBitIsZero(N0))
-    return DAG.getNode(ISD::SINT_TO_FP, dl, Op.getValueType(), N0);
-
   if (Op.getSimpleValueType().isVector())
     return lowerUINT_TO_FP_vec(Op, DAG);