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[SelectionDAGISel] Don't merge input chains if it would put a token factor in the way of a glue. #167805

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Merged
topperc merged 5 commits into from
Nov 13, 2025
Merged

[SelectionDAGISel] Don't merge input chains if it would put a token factor in the way of a glue. #167805

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712fd9f
[SelectionDAGISel] Don't merge input chains if it would put a token f…
topperc Nov 13, 2025
2caeb4a
fixup! clang-format
topperc Nov 13, 2025
4e40c83
Merge remote-tracking branch 'origin/main' into pr/63790
topperc Nov 13, 2025
1c7edce
fixup! Add CHECK lines
topperc Nov 13, 2025
0f7f551
fixup! Adjust comment
topperc Nov 13, 2025
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18 changes: 13 additions & 5 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2782,8 +2782,8 @@ void SelectionDAGISel::UpdateChains(
/// induce cycles in the DAG) and if so, creating a TokenFactor node. that will
/// be used as the input node chain for the generated nodes.
static SDValue
HandleMergeInputChains(SmallVectorImpl<SDNode*> &ChainNodesMatched,
SelectionDAG *CurDAG) {
HandleMergeInputChains(SmallVectorImpl<SDNode *> &ChainNodesMatched,
SDValue InputGlue, SelectionDAG *CurDAG) {

SmallPtrSet<const SDNode *, 16> Visited;
SmallVector<const SDNode *, 8> Worklist;
Expand Down Expand Up @@ -2826,8 +2826,16 @@ HandleMergeInputChains(SmallVectorImpl<SDNode*> &ChainNodesMatched,
// node that is both the predecessor and successor of the
// to-be-merged nodes. Fail.
Visited.clear();
for (SDValue V : InputChains)
for (SDValue V : InputChains) {
// If we need to create a TokenFactor, and any of the input chains will
// also be glued to the output, we cannot merge the chains. The TokenFactor
// would prevent the glue from being honored.
if (InputChains.size() != 1 &&
V->getValueType(V->getNumValues() - 1) == MVT::Glue &&
InputGlue.getNode() == V.getNode())
return SDValue();
Worklist.push_back(V.getNode());
}

for (auto *N : ChainNodesMatched)
if (SDNode::hasPredecessorHelper(N, Visited, Worklist, Max, true))
Expand Down Expand Up @@ -3989,7 +3997,7 @@ void SelectionDAGISel::SelectCodeCommon(SDNode *NodeToMatch,
}

// Merge the input chains if they are not intra-pattern references.
InputChain = HandleMergeInputChains(ChainNodesMatched, CurDAG);
InputChain = HandleMergeInputChains(ChainNodesMatched, InputGlue, CurDAG);

if (!InputChain.getNode())
break; // Failed to merge.
Expand Down Expand Up @@ -4033,7 +4041,7 @@ void SelectionDAGISel::SelectCodeCommon(SDNode *NodeToMatch,
break;

// Merge the input chains if they are not intra-pattern references.
InputChain = HandleMergeInputChains(ChainNodesMatched, CurDAG);
InputChain = HandleMergeInputChains(ChainNodesMatched, InputGlue, CurDAG);

if (!InputChain.getNode())
break; // Failed to merge.
Expand Down
10 changes: 10 additions & 0 deletions llvm/test/CodeGen/X86/pr63790.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
; RUN: llc < %s -mtriple=x86_64 | FileCheck %s

define void @f(ptr %0, i64 %1) {
BB:
%fps = load <2 x ptr>, ptr %0
%fp = extractelement <2 x ptr> %fps, i64 %1
%p = call ptr %fp(i32 42)
store <2 x ptr> %fps, ptr %p
ret void
}
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