Disable neon for armhf if not supported by C/C++ compiler #2672
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jemc
approved these changes
Apr 30, 2018
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We discussed at sync and no one felt knowledgeable enough to merge. @sylvanc or @Praetonus perhaps. |
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This looks good! Thank you @ikavalio |
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Hi, this minor PR is a workaround for llvm's bug 30842. The issue is that
neoninstructions are enabled by default for armhf even if target CPU doesn't support them. As a result llvm backend may generate code that has unsupported instructions and program can crash with SIGILL.It's not a big issue for ponyc as neon can be disabled with
ponyc --features=-neon, but it's problematic forlibponycunit tests as compilation target is configured automatically and neon can't be disabled easily for such cases. As a result unit tests are failing on tests likeBoxedTupleIsBoxedTuplewhere vectorisation is used which isn't great.My current solution is to disable neon by default (setting
--features=for ponyc explicitly will revert the behavior) if neon instruction set was disabled for C/C++ compiler. I created a new var in Makefilefputhat corresponds to-mfpuflag and can be redefined for arm targets, otherwise it doesn't have any effect.I hope it makes sense.