[llvm] 03a2fe9 - [DAG] visitSUB - update the ABS matching code to use SDPatternMatch and hasOperation.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2024-06-06T10:06:57+01:00
New Revision: 03a2fe9a7574c0cff724666e713dead7009a9621

URL: https://github.com/llvm/llvm-project/commit/03a2fe9a7574c0cff724666e713dead7009a9621
DIFF: https://github.com/llvm/llvm-project/commit/03a2fe9a7574c0cff724666e713dead7009a9621.diff

LOG: [DAG] visitSUB - update the ABS matching code to use SDPatternMatch and hasOperation.

Avoids the need to explicitly test both commuted variants and doesn't match custom lowering after legalization.

Cleanup for #94504

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 9a5359015439e..02cd125eeff09 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4041,17 +4041,11 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
     return DAG.getNode(ISD::ADD, DL, VT, N0, SExt);
   }
 
-  // fold Y = sra (X, size(X)-1); sub (xor (X, Y), Y) -> (abs X)
-  if (TLI.isOperationLegalOrCustom(ISD::ABS, VT)) {
-    if (N0.getOpcode() == ISD::XOR && N1.getOpcode() == ISD::SRA) {
-      SDValue X0 = N0.getOperand(0), X1 = N0.getOperand(1);
-      SDValue S0 = N1.getOperand(0);
-      if ((X0 == S0 && X1 == N1) || (X0 == N1 && X1 == S0))
-        if (ConstantSDNode *C = isConstOrConstSplat(N1.getOperand(1)))
-          if (C->getAPIntValue() == (BitWidth - 1))
-            return DAG.getNode(ISD::ABS, DL, VT, S0);
-    }
-  }
+  // fold B = sra (A, size(A)-1); sub (xor (A, B), B) -> (abs A)
+  if (hasOperation(ISD::ABS, VT) &&
+      sd_match(N1, m_Sra(m_Value(A), m_SpecificInt(BitWidth - 1))) &&
+      sd_match(N0, m_Xor(m_Specific(A), m_Specific(N1))))
+    return DAG.getNode(ISD::ABS, DL, VT, A);
 
   // If the relocation model supports it, consider symbol offsets.
   if (GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(N0))