[DAGCombiner] Limit steps in shouldCombineToPostInc #116030
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@llvm/pr-subscribers-llvm-selectiondag Author: Jonathan Cohen (jcohen-apple) ChangesCurrently the function will walk the entire DAG to find other candidates to perform a post-inc store. This leads to very long compilation times on large functions. Added a MaxSteps limit to avoid this, which is also aligned to how hasPredecessorHelper is used elsewhere in the code. Full diff: https://github.com/llvm/llvm-project/pull/116030.diff 1 Files Affected:
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 6059229cd6d9a4..cc51aed40003f0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -19089,7 +19089,8 @@ static bool shouldCombineToPostInc(SDNode *N, SDValue Ptr, SDNode *PtrUse,
IsMasked, OtherPtr, TLI)) {
SmallVector<const SDNode *, 2> Worklist;
Worklist.push_back(Use);
- if (SDNode::hasPredecessorHelper(N, Visited, Worklist))
+ constexpr unsigned int MaxSteps = 8192;
+ if (SDNode::hasPredecessorHelper(N, Visited, Worklist, MaxSteps))
return false;
}
}
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arsenm
reviewed
Nov 13, 2024
| SmallVector<const SDNode *, 2> Worklist; | ||
| Worklist.push_back(Use); | ||
| if (SDNode::hasPredecessorHelper(N, Visited, Worklist)) | ||
| constexpr unsigned int MaxSteps = 8192; |
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Big number to repeat multiple times. Move these to a common constant?
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I changed it to be a hidden cl option in case someone would like to play with it later, and defaulted to 8192. WDYT?
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Currently the function will walk the entire DAG to find other candidates to perform a post-inc store. This leads to very long compilation times on large functions. Added a MaxSteps limit to avoid this, which is also aligned to how hasPredecessorHelper is used elsewhere in the code.
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Currently the function will walk the entire DAG to find other candidates to perform a post-inc store. This leads to very long compilation times on large functions. Added a MaxSteps limit to avoid this, which is also aligned to how hasPredecessorHelper is used elsewhere in the code.