These tests just don't check the output written to the current directory. The
current directory may be write protected e.g. in a sandboxed environment.
The Testcases that use -emit-llvm and -verify only care about stdout/stderr
and are in this patch changed to use -emit-llvm-only to avoid writing to an
output file. The verify-inlineasmbr.mir testcase that also only care about
stdout/stderr is in this patch changed to throw away the output file and just
write to /dev/null.
Test for a case we observed after the initial implementation of D129997
landed, in which case we observed a crash while building the ppc64le
Linux kernel. In that case, we had one block with two exits, both to the
same successor. Removing one of the exits corrupted the
successor/predecessor lists.
So when we have an INLINEASM_BR, check a few things for each indirect
target:
1. that it exists.
2. that it is listed in our successors.
3. that its predecessor list contains the parent MBB of INLINEASM_BR.
This would have caught the regression discovered after D129997 landed,
after the pass that was problematic (early-tailduplication) rather than
getting a stack trace in a later pass (regalloc) that doesn't understand
the anomaly and crashes.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D130290
