[llvm] r302651 - [DAGCombiner] Dropped explicit (sra 0, x) -> 0 and (sra -1, x) -> 0 folds.

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Wed May 10 08:06:26 2017
New Revision: 302651

URL: http://llvm.org/viewvc/llvm-project?rev=302651&view=rev
Log:
[DAGCombiner] Dropped explicit (sra 0, x) -> 0 and (sra -1, x) -> 0 folds.

These are both handled (and tested) by the earlier ComputeNumSignBits == EltSizeInBits fold.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=302651&r1=302650&r2=302651&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Wed May 10 08:06:26 2017
@@ -5534,6 +5534,8 @@ SDValue DAGCombiner::visitSRA(SDNode *N)
   }
 
   // Arithmetic shifting an all-sign-bit value is a no-op.
+  // fold (sra 0, x) -> 0
+  // fold (sra -1, x) -> -1
   if (DAG.ComputeNumSignBits(N0) == OpSizeInBits)
     return N0;
 
@@ -5548,12 +5550,6 @@ SDValue DAGCombiner::visitSRA(SDNode *N)
   ConstantSDNode *N0C = getAsNonOpaqueConstant(N0);
   if (N0C && N1C && !N1C->isOpaque())
     return DAG.FoldConstantArithmetic(ISD::SRA, SDLoc(N), VT, N0C, N1C);
-  // fold (sra 0, x) -> 0
-  if (isNullConstant(N0))
-    return N0;
-  // fold (sra -1, x) -> -1
-  if (isAllOnesConstant(N0))
-    return N0;
   // fold (sra x, c >= size(x)) -> undef
   if (N1C && N1C->getAPIntValue().uge(OpSizeInBits))
     return DAG.getUNDEF(VT);