[all-commits] [llvm/llvm-project] 1fb24f: Reland [clang] Pass -clear-ast-before-backend in C...

[aeubanks via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1fb24fe85a19ae71b00875ff6c96ef1831dcf7e3
      https://github.com/llvm/llvm-project/commit/1fb24fe85a19ae71b00875ff6c96ef1831dcf7e3
  Author: Arthur Eubanks <aeubanks at google.com>
  Date:   2021-10-18 (Mon, 18 Oct 2021)

  Changed paths:
    M clang/lib/Driver/ToolChains/Clang.cpp
    M clang/lib/Interpreter/Interpreter.cpp

  Log Message:
  -----------
  Reland [clang] Pass -clear-ast-before-backend in Clang::ConstructJob()

This clears the memory used for the Clang AST before we run LLVM passes.

https://llvm-compile-time-tracker.com/compare.php?from=d0a5f61c4f6fccec87fd5207e3fcd9502dd59854&to=b7437fee79e04464dd968e1a29185495f3590481&stat=max-rss
shows significant memory savings with no slowdown (in fact -O0 slightly speeds up).

For more background, see
https://lists.llvm.org/pipermail/cfe-dev/2021-September/068930.html.

Turn this off for the interpreter since it does codegen multiple times.

Relanding with fix for -print-stats: D111973

Differential Revision: https://reviews.llvm.org/D111270