[PATCH] D70676: [DebugInfo] Don't repeatedly created undef DBG_VALUEs during machine-sinking

[Hans Wennborg via Phabricator via llvm-commits]

hans added a comment.

We're seeing non-determinism in Chromium builds after this commit. You can reproduce using the pre-processed source from https://bugs.chromium.org/p/chromium/issues/detail?id=1032241#c32 and running this (giant, sorry) command:

  $ for x in {1..25} ; do build.release/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -disable-llvm-verifier -discard-value-names -mrelocation-model pic -pic-level 2 -mthread-model posix -fmerge-all-constants -mframe-pointer=all -relaxed-aliasing -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -target-feature +sse2 -dwarf-column-info -debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb -O2 -std=c++14 -fno-operator-names -ftrivial-auto-var-init=pattern -fno-rtti -fgnuc-version=4.2.1 -Qn -vectorize-loops -vectorize-slp -fcomplete-member-pointers /tmp/a.ii -o /tmp/foo_$x.o & done && wait && sha1sum /tmp/foo_*.o

This should print 25 identical sha1 hashes for the 25 object files, but some of them have different hashes.

I believe this might be due to iteration over one of the DenseMaps, which is in non-deterministic order.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D70676/new/

https://reviews.llvm.org/D70676