[CIR][CodeGen] Removed special handling for array of union #1780
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andykaylor
approved these changes
Aug 6, 2025
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Thanks for the review @andykaylor, I applied the requested changes. |
Special handling for array of union was forcing all non-union C arrays to be emitted as CIR arrays, which differs from OG CodeGen, where some arrays are emitted as structs.
…e handling result
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Rebased on top of latest rebase. |
| @@ -1159,8 +1117,7 @@ class ConstExprEmitter | |||
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| if (i == 0) | |||
| CommonElementType = C.getType(); | |||
| else if (isDesiredArrayOfUnionDirectly && | |||
| C.getType() != CommonElementType) | |||
| else if (C.getType() != CommonElementType) | |||
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It's worth adding a comment here to briefly mention how we deviate from OG (absence of isDesiredArrayOfUnionDirectly)
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From when I looked into this: this code isn't why we deviate from OG CodeGen. We deviate because OG 'optimizes' emission of structs with homogeneous field types to an array of the field type. I couldn't find a good heuristic for exactly when they do/don't do that so I didn't include a fix and just reverted the changes (to get rid of lowering crashes). I think a comment about that here may lead folks down the wrong road to fixing the issue, because it should to be handled when we lower to LLVM, not when we generate CIR.
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I noticed a linux failure, is that related? |
Looks like they're all errors in clang-tidy: I can look into it in the morning. |
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Special handling for array of unions was forcing all non-union C arrays to be emitted as CIR arrays, which differs from OG CodeGen, where array may be emitted as LLVM struct.
Closes #1315