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[PowerPC] Change default for unaligned FP access for older subtargets
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Authored by nemanjai on Dec 27 2019, 8:14 PM.

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Summary

This is a fix for https://bugs.llvm.org/show_bug.cgi?id=40554

Some CPU's trap to the kernel on unaligned floating point access and there are kernels that do not handle the interrupt. The program then fails with a SIGBUS according to the PR. This just switches the default for unaligned access to only allow it on recent server CPUs that are known to allow this.

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nemanjai created this revision.Dec 27 2019, 8:14 PM
Herald added a project: Restricted Project. · View Herald TranscriptDec 27 2019, 8:14 PM
nemanjai updated this revision to Diff 235458.Dec 27 2019, 8:15 PM

Add the feature to the BG cores as well.

hfinkel accepted this revision as: hfinkel.Dec 28 2019, 8:49 AM

Add the feature to the BG cores as well.

BG did allow this, but IIRC, only some finite number of times (before it really slowed down by logging a lot from the kernel). Maybe this was just for the vector types, but regardless, I'd leave this off for the BG cores.

Otherwise, LGTM.

This revision is now accepted and ready to land.Dec 28 2019, 8:49 AM
This revision was automatically updated to reflect the committed changes.