[all-commits] [llvm/llvm-project] efcb07: [llvm][Support] Avoid intermediate heap allocation...

[Jan Svoboda via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: efcb07bf6e5fb0ff12e5855ab0ad86cd534d5578
      https://github.com/llvm/llvm-project/commit/efcb07bf6e5fb0ff12e5855ab0ad86cd534d5578
  Author: Jan Svoboda <jan_svoboda at apple.com>
  Date:   2023-08-03 (Thu, 03 Aug 2023)

  Changed paths:
    M llvm/include/llvm/Support/StringSaver.h
    M llvm/lib/Support/StringSaver.cpp

  Log Message:
  -----------
  [llvm][Support] Avoid intermediate heap allocations in `StringSaver`

The `Twine::str()` function currently always allocates heap memory via `std::string`. However, some instances of `Twine` don't need an intermediate buffer at all, and the rest can attempt to print into a stack buffer first.

This is intentionally not making use of `Twine::isSingleStringLiteral()` from D157010 to skip saving the string in the bump-pointer allocator, since the `StringSaver` documentation suggests that MUST happen for every given string.

Reviewed By: benlangmuir

Differential Revision: https://reviews.llvm.org/D157015