[PATCH] D57190: [MC] Teach the MachO object writer about N_FUNC_COLD

[Vedant Kumar via Phabricator via llvm-commits]

vsk created this revision.
vsk added reviewers: lhames, thegameg, kledzik.
Herald added subscribers: rupprecht, hiraditya, javed.absar.

N_FUNC_COLD is a new MachO symbol attribute. It's a hint to the linker
to order a symbol towards the end of its section, to improve locality.

Example:

  void a1() {}
  __attribute__((cold)) void a2() {}
  void a3() {}
  int main() {
    a1();
    a2();
    a3();
    return 0;
  }

A linker that supports N_FUNC_COLD will order _a2 to the end of the text
section. From `nm -njU` output, we see:

  _a1
  _a3
  _main
  _a2


https://reviews.llvm.org/D57190

Files:
  llvm/include/llvm/BinaryFormat/MachO.h
  llvm/include/llvm/MC/MCDirectives.h
  llvm/include/llvm/MC/MCSymbolMachO.h
  llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  llvm/lib/MC/MCAsmStreamer.cpp
  llvm/lib/MC/MCELFStreamer.cpp
  llvm/lib/MC/MCMachOStreamer.cpp
  llvm/test/tools/llvm-nm/AArch64/Inputs/cold-func.ll
  llvm/test/tools/llvm-nm/AArch64/macho-cold.test
  llvm/tools/llvm-nm/llvm-nm.cpp

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