[llvm] 15e2be2 - [DAG] visitMULHS/MULHU/AND - remove some redundant LHS constant checks

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2022-01-25T11:54:23Z
New Revision: 15e2be291f7fc8a694f796dd494e4f14d7f5a982

URL: https://github.com/llvm/llvm-project/commit/15e2be291f7fc8a694f796dd494e4f14d7f5a982
DIFF: https://github.com/llvm/llvm-project/commit/15e2be291f7fc8a694f796dd494e4f14d7f5a982.diff

LOG: [DAG] visitMULHS/MULHU/AND - remove some redundant LHS constant checks

Now that we constant fold and canonicalize constants to the RHS, we don't need to check both LHS and RHS for specific constants

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c3d2ed2dcf85..082e2508aa4b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4470,15 +4470,15 @@ SDValue DAGCombiner::visitMULHS(SDNode *N) {
       return FoldedVOp;
 
     // fold (mulhs x, 0) -> 0
-    // do not return N0/N1, because undef node may exist.
-    if (ISD::isConstantSplatVectorAllZeros(N0.getNode()) ||
-        ISD::isConstantSplatVectorAllZeros(N1.getNode()))
+    // do not return N1, because undef node may exist.
+    if (ISD::isConstantSplatVectorAllZeros(N1.getNode()))
       return DAG.getConstant(0, DL, VT);
   }
 
   // fold (mulhs x, 0) -> 0
   if (isNullConstant(N1))
     return N1;
+
   // fold (mulhs x, 1) -> (sra x, size(x)-1)
   if (isOneConstant(N1))
     return DAG.getNode(ISD::SRA, DL, N0.getValueType(), N0,
@@ -4530,18 +4530,19 @@ SDValue DAGCombiner::visitMULHU(SDNode *N) {
       return FoldedVOp;
 
     // fold (mulhu x, 0) -> 0
-    // do not return N0/N1, because undef node may exist.
-    if (ISD::isConstantSplatVectorAllZeros(N0.getNode()) ||
-        ISD::isConstantSplatVectorAllZeros(N1.getNode()))
+    // do not return N1, because undef node may exist.
+    if (ISD::isConstantSplatVectorAllZeros(N1.getNode()))
       return DAG.getConstant(0, DL, VT);
   }
 
   // fold (mulhu x, 0) -> 0
   if (isNullConstant(N1))
     return N1;
+
   // fold (mulhu x, 1) -> 0
   if (isOneConstant(N1))
     return DAG.getConstant(0, DL, N0.getValueType());
+
   // fold (mulhu x, undef) -> 0
   if (N0.isUndef() || N1.isUndef())
     return DAG.getConstant(0, DL, VT);
@@ -5815,18 +5816,12 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
       return FoldedVOp;
 
     // fold (and x, 0) -> 0, vector edition
-    if (ISD::isConstantSplatVectorAllZeros(N0.getNode()))
-      // do not return N0, because undef node may exist in N0
-      return DAG.getConstant(APInt::getZero(N0.getScalarValueSizeInBits()),
-                             SDLoc(N), N0.getValueType());
     if (ISD::isConstantSplatVectorAllZeros(N1.getNode()))
       // do not return N1, because undef node may exist in N1
       return DAG.getConstant(APInt::getZero(N1.getScalarValueSizeInBits()),
                              SDLoc(N), N1.getValueType());
 
     // fold (and x, -1) -> x, vector edition
-    if (ISD::isConstantSplatVectorAllOnes(N0.getNode()))
-      return N1;
     if (ISD::isConstantSplatVectorAllOnes(N1.getNode()))
       return N0;