[PATCH] D71639: [ELF][PPC64] Improve "call lacks nop" diagnostic and make it compatible with GCC<5.5 and GCC<6.4

[Sean Fertile via Phabricator via llvm-commits]

sfertile added a comment.

I can definitely see it from the opposite side: We want LLD to be usable on these systems that shipped with this bug in libstdc++ and gcc/gfortran. And adding a link option can be hard to do in some build setups so its not as simple as I make it sound. What worries me though is that one of the compilers could subtly break and with the linker[s] being sloppy with the error then we don't find out until long after the toolchain has shipped.

I  think you are right that this will only be triggered on handwritten assembly right now. That is still useful even though not many people write assembly now days. Even experts can mess up, for example taking code written for an executable, then linking it into a shared object since it //looks// like its already position independent could trigger this error because a tail-call that was valid in an exec isn't in the shared object. These kinds of details aren't really documented anywhere. They are difficult to figure out with the error, but much much worse when you are diagnosing runtime corruptions.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D71639/new/

https://reviews.llvm.org/D71639