llvm: change data layout bug to an error and make it trigger more #120062
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Don't skip the inconsistent data layout check for custom LLVMs. With rust-lang#118708, all targets will have a simple test that would trigger this check if LLVM's data layouts do change - so data layouts would be corrected during the LLVM upgrade. Therefore, with builtin targets, this check won't trigger with our LLVM because each target will have been confirmed to work. With non-builtin targets, this check is probably useful to have because you can change the data layout in your target and if its wrong then that could lead to bugs. When using a custom LLVM, the same justification makes sense for non-builtin targets as with our LLVM, the user can update their target to match their LLVM and that's probably a good thing to do. However, with a custom LLVM, the user cannot change the builtin target data layouts if they don't match - though given that the compiler's data layout is used for layout computation and a bunch of other things - you could get some bugs because of the mismatch and probably want to know about that. `CFG_LLVM_ROOT` was also always set during local development with `download-ci-llvm` so this bug would never trigger locally. Signed-off-by: David Wood <david@davidtw.co>
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Thanks @davidtwco! @bors r+ |
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Finished benchmarking commit (8af70c7): comparison URL. Overall result: no relevant changes - no action needed@rustbot label: -perf-regression Instruction countThis benchmark run did not return any relevant results for this metric. Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
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Fixes #33446.
Don't skip the inconsistent data layout check for custom LLVMs or non-built-in targets.
With #118708, all targets will have a simple test that would trigger this error if LLVM's data layouts do change - so data layouts would be corrected during the LLVM upgrade. Therefore, with builtin targets, this error won't happen with our LLVM because each target will have been confirmed to work. With non-builtin targets, this error is probably useful to have because you can change the data layout in your target and if it is wrong then that could lead to bugs.
When using a custom LLVM, the same justification makes sense for non-builtin targets as with our LLVM, the user can update their target to match their LLVM and that's probably a good thing to do. However, with a custom LLVM, the user cannot change the builtin target data layouts if they don't match - though given that the compiler's data layout is used for layout computation and a bunch of other things - you could get some bugs because of the mismatch and probably want to know about that. I'm not sure if this is something that people do and is okay, but I doubt it?
CFG_LLVM_ROOTwas also always set during local development withdownload-ci-llvmso this bug would never trigger locally.In #33446, two points are raised:
bug!to a proper error is what is suggested, by usingisCompatibleDataLayoutfrom LLVM, but that function still just does the same thing that we do and check for equality, so I've avoided the additional code necessary to do that FFI call.