[PATCH] D80391: [Driver] Don't make -gsplit-dwarf imply -g2

[Bob Haarman via Phabricator via cfe-commits]

inglorion added a comment.

For Chrome on Chrome OS, this is https://crbug.com/1158215

Here, we saw our links fail with "output file too large". Investigation revealed that debug info was being included in the binary, instead of in .dwo files as expected. That turned out to be caused by this change.

It seems that there are cases where -gsplit-dwarf is passed, but it does not take effect because there isn't also a -g (or -g<level>) option:

  clang -c -fthinlto-index=foo.o.thinlto.bc -gsplit-dwarf foo.o -o foo.bin.o

Shows no .dwo file and debug info in foo.bin.o, whereas

  clang -c -fthinlto-index=foo.o.thinlto.bc -gsplit-dwarf -g foo.o -o foo.bin.o

shows a .dwo file which is referenced from foo.bin.o

The only thing that is different here is that the latter command has "-g" whereas the former doesn't.

In other words, the new implementation still doesn't make -g and -gsplit-dwarf fully orthogonal; instead of -gsplit-dwarf always turning on debug fission, it *only* turns it on when there is also a -g or -g<level> option - at least in distributed ThinLTO code generation.

It seems that orthogonality was the motivation for this change, and that -gsplit-dwarf without -g is supposed to work in the linker (per MaskRay's comment about -g being ignored by the linker).

Can we make it so that -gsplit-dwarf turns on debug fission and we then use that even if no -g options were passed?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80391/new/

https://reviews.llvm.org/D80391