r308867 | dim | 2016-11-19 22:05:17 +0100 (Sat, 19 Nov 2016) | 15 lines

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

Index: lib/Target/X86/X86CallFrameOptimization.cpp
===================================================================
--- lib/Target/X86/X86CallFrameOptimization.cpp	(revision 308866)
+++ lib/Target/X86/X86CallFrameOptimization.cpp	(revision 308867)
@@ -125,6 +125,11 @@ bool X86CallFrameOptimization::isLegal(MachineFunc
   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.