| Issue |
140745
|
| Summary |
[DAG] SDPatternMatch - m_Zero can't see through bitcasts
|
| Labels |
good first issue,
llvm:codegen
|
| Assignees |
|
| Reporter |
RKSimon
|
X86 uses ISD::isBuildVectorAllZeros to peek through bitcasts to match zero vectors in a large number of combines.
Ideally we'd use SDPatternMatch to match these combines and use m_Zero() instead, but regrettably this fails to match the zero vectors through bitcasts,
https://github.com/llvm/llvm-project/commit/84397c61f44e62231d1876a745a0c1f74ea8a5b8 shows an example of the regression
If we convert m_Zero() to something closer to m_AllOnes / AllOnes_match we might be able to make this work.
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