[llvm] ba1255d - [DAG] Use FoldConstantArithmetic to constant fold (and (ext (and V, c1)), c2) -> (and (ext V), (and c1, (ext c2)))

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2024-10-20T13:05:23+01:00
New Revision: ba1255def64a9c3c68d97ace051eec76f546eeb0

URL: https://github.com/llvm/llvm-project/commit/ba1255def64a9c3c68d97ace051eec76f546eeb0
DIFF: https://github.com/llvm/llvm-project/commit/ba1255def64a9c3c68d97ace051eec76f546eeb0.diff

LOG: [DAG] Use FoldConstantArithmetic to constant fold (and (ext (and V, c1)), c2) -> (and (ext V), (and c1, (ext c2)))

Noticed while triaging the regression from #112710 noticed by @mstorsjo - don't rely on isConstantIntBuildVectorOrConstantInt+getNode to guarantee constant folding (if it fails to constant fold it will infinite loop), use FoldConstantArithmetic instead.

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 f89734fb43e983..2527bb269643bb 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7159,15 +7159,16 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
     SDValue N0Op0 = N0.getOperand(0);
     if (N0Op0.getOpcode() == ISD::AND &&
         (ExtOpc != ISD::ZERO_EXTEND || !TLI.isZExtFree(N0Op0, VT)) &&
-        DAG.isConstantIntBuildVectorOrConstantInt(N1) &&
-        DAG.isConstantIntBuildVectorOrConstantInt(N0Op0.getOperand(1)) &&
         N0->hasOneUse() && N0Op0->hasOneUse()) {
-      SDValue NewMask =
-          DAG.getNode(ISD::AND, DL, VT, N1,
-                      DAG.getNode(ExtOpc, DL, VT, N0Op0.getOperand(1)));
-      return DAG.getNode(ISD::AND, DL, VT,
-                         DAG.getNode(ExtOpc, DL, VT, N0Op0.getOperand(0)),
-                         NewMask);
+      if (SDValue NewExt = DAG.FoldConstantArithmetic(ExtOpc, DL, VT,
+                                                      {N0Op0.getOperand(1)})) {
+        if (SDValue NewMask =
+                DAG.FoldConstantArithmetic(ISD::AND, DL, VT, {N1, NewExt})) {
+          return DAG.getNode(ISD::AND, DL, VT,
+                             DAG.getNode(ExtOpc, DL, VT, N0Op0.getOperand(0)),
+                             NewMask);
+        }
+      }
     }
   }