[llvm-branch-commits] [llvm] [llvm][IR] Treat memcmp and bcmp as libcalls (PR #135706)

[Eli Friedman via llvm-branch-commits]

efriedma-quic wrote:

I don't really want to start adding functions to RuntimeLibcalls.def piecemeal without documented criteria for what, exactly, should be added.  Do we need to add every single function that any transformation can generate under any circumstances?  Or is there some criteria we can use to restrict this?  I mean, we do memcmp->bcmp, yes, but we also touch a bunch of other math and I/O functions.  Do we need to add all the functions from BuildLibCalls.h?

Certain libcalls are special because we can generate calls to them even with -fno-builtins: there is no alternative implementation.  Like for memcpy, or __stack_chk_fail, or floating-point arithmetic on soft-float targets.  memcmp isn't special like this.

https://github.com/llvm/llvm-project/pull/135706