[PATCH] D155790: PreISelIntrinsicLowering: don't expand memcpys in minsize functions, even with no-builtins.

Sun Jul 23 20:21:43 PDT 2023

efriedma added a comment.

As far as I know, before 3c848194f28decca41b7362f9dd35d4939797724 <https://reviews.llvm.org/rG3c848194f28decca41b7362f9dd35d4939797724>, things worked the following way:

- LLVM optimizations wouldn't introduce llvm.memcpy calls into nobuiltin functions.
- Any llvm.memcpy calls written explicitly in the input IR expand to "memcpy" (which we assume the user provides if necessary).

Maybe you could argue the latter behavior is a "bug", but it's behavior we provided for many years, and users depend on it.  (And it's gcc-compatible.)

3c848194f28decca41b7362f9dd35d4939797724 <https://reviews.llvm.org/rG3c848194f28decca41b7362f9dd35d4939797724> changes things so that instead of calling "memcpy", we generate a bunch of terrible inline code.  This apparently landed without review?

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D155790/new/

https://reviews.llvm.org/D155790