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Work around LLVM PR30879, which is about a bad interaction between X86

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Call Frame Optimization on i386 and libunwind, by disallowing the
optimization for i386-freebsd12.

This should fix some instances of broken exception handling when frame
pointers are omitted, in particular some unittests run during the build
of editors/libreoffice.

This hack will be removed as soon as upstream has implemented a more
permanent fix for this problem.

Upstream PR:	https://llvm.org/bugs/show_bug.cgi?id=30879
Reviewed by:	emaste
PR:		212343
This commit is contained in:
Dimitry Andric 2016-11-19 21:05:17 +00:00
parent 67bc8c8b9e
commit f1d9b58cd4
1 changed files with 5 additions and 0 deletions
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5
contrib/llvm/lib/Target/X86/X86CallFrameOptimization.cpp
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@ -125,6 +125,11 @@ bool X86CallFrameOptimization::isLegal(MachineFunction &MF) {
if (NoX86CFOpt.getValue())
return false;
// Work around LLVM PR30879 (bad interaction between CFO and libunwind)
if (STI->isTargetFreeBSD() && STI->is32Bit() &&
STI->getTargetTriple().getOSMajorVersion() >= 12)
return false;
// We can't encode multiple DW_CFA_GNU_args_size or DW_CFA_def_cfa_offset
// in the compact unwind encoding that Darwin uses. So, bail if there
// is a danger of that being generated.