[all-commits] [llvm/llvm-project] a10300: [libc] Allow customization of memcpy via flags.

[Guillaume Chatelet via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a10300a2b27c426556f9266364337d5d546a3c14
      https://github.com/llvm/llvm-project/commit/a10300a2b27c426556f9266364337d5d546a3c14
  Author: Guillaume Chatelet <gchatelet at google.com>
  Date:   2021-01-15 (Fri, 15 Jan 2021)

  Changed paths:
    M libc/src/__support/common.h
    M libc/src/string/x86/memcpy.cpp

  Log Message:
  -----------
  [libc] Allow customization of memcpy via flags.

 - Adds LLVM_LIBC_IS_DEFINED macro to libc/src/__support/common.h
 - Adds a few knobs to memcpy to help with experimentations:
   - LLVM_LIBC_MEMCPY_X86_USE_ONLY_REPMOVSB replaces the implementation with a single call to rep;movsb
   - LLVM_LIBC_MEMCPY_X86_USE_REPMOVSB_FROM_SIZE customizes where the usage of rep;movsb

Differential Revision: https://reviews.llvm.org/D94692