[llvm] d037445 - [DAG] visitSHL - use FoldConstantArithmetic to fold constants in (shl (add x, c1), c2) -> (add (shl x, c2), c1 << c2) fold

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2023-08-29T18:52:24+01:00
New Revision: d037445f3a2c6dc1842b5bfc1d5d81988c2f223d

URL: https://github.com/llvm/llvm-project/commit/d037445f3a2c6dc1842b5bfc1d5d81988c2f223d
DIFF: https://github.com/llvm/llvm-project/commit/d037445f3a2c6dc1842b5bfc1d5d81988c2f223d.diff

LOG: [DAG] visitSHL - use FoldConstantArithmetic to fold constants in (shl (add x, c1), c2) -> (add (shl x, c2), c1 << c2) fold

Matches what we do in the (shl (mul x, c1), c2) -> (mul x, c1 << c2) fold as well as inside visitShiftByConstant

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 b1612ae5a7f3ac..55de08bd4a357d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -9917,15 +9917,14 @@ SDValue DAGCombiner::visitSHL(SDNode *N) {
   // Variant of version done on multiply, except mul by a power of 2 is turned
   // into a shift.
   if ((N0.getOpcode() == ISD::ADD || N0.getOpcode() == ISD::OR) &&
-      N0->hasOneUse() &&
-      isConstantOrConstantVector(N1, /* No Opaques */ true) &&
-      isConstantOrConstantVector(N0.getOperand(1), /* No Opaques */ true) &&
-      TLI.isDesirableToCommuteWithShift(N, Level)) {
-    SDValue Shl0 = DAG.getNode(ISD::SHL, SDLoc(N0), VT, N0.getOperand(0), N1);
-    SDValue Shl1 = DAG.getNode(ISD::SHL, SDLoc(N1), VT, N0.getOperand(1), N1);
-    AddToWorklist(Shl0.getNode());
-    AddToWorklist(Shl1.getNode());
-    return DAG.getNode(N0.getOpcode(), SDLoc(N), VT, Shl0, Shl1);
+      N0->hasOneUse() && TLI.isDesirableToCommuteWithShift(N, Level)) {
+    SDValue N01 = N0.getOperand(1);
+    if (SDValue Shl1 =
+            DAG.FoldConstantArithmetic(ISD::SHL, SDLoc(N1), VT, {N01, N1})) {
+      SDValue Shl0 = DAG.getNode(ISD::SHL, SDLoc(N0), VT, N0.getOperand(0), N1);
+      AddToWorklist(Shl0.getNode());
+      return DAG.getNode(N0.getOpcode(), SDLoc(N), VT, Shl0, Shl1);
+    }
   }
 
   // fold (shl (mul x, c1), c2) -> (mul x, c1 << c2)