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llvm / llvm-project / 9186df9b088f425182c58c7eee23645a77d7591c
commit9186df9b088f425182c58c7eee23645a77d7591c[log] [tgz]
authorTobias Stadler <mail@stadler-tobias.de>Tue Jun 24 14:15:27 2025 +0100
committerGitHub <noreply@github.com>Tue Jun 24 14:15:27 2025 +0100
treea1c70494539b8563b8256281697b1af0c7032ddc
parente04c938cc08a90ae60440ce22d072ebc69d67ee8 [diff]
[InlineCost] Simplify extractvalue across callsite (#145054)

Motivation: When using libc++, `std::bitset<64>::count()` doesn't
optimize to a single popcount instruction on AArch64, because we fail to
inline the library code completely. Inlining fails, because the internal
bit_iterator struct is passed as a [2 x i64] %arg value on AArch64. The
value is built using insertvalue instructions and only one of the array
entries is constant. If we know that this entry is constant, we can
prove that half the function becomes dead. However, InlineCost only
considers operands for simplification if they are Constants, which %arg
is not. Without this simplification the function is too expensive to
inline.

Therefore, we had to teach InlineCost to support non-Constant simplified values
(PR #145083). Now, we enable this for extractvalue, because we want to simplify
the extractvalue with the insertvalues from the caller function. This is enough to
get bitset::count fully optimized.

There are similar opportunities we can explore for BinOps in the future
(e.g. cmp eq %arg1, %arg2 when the caller passes the same value into
both arguments), but we need to be careful here, because InstSimplify
isn't completely safe to use with operands owned by different functions.
2 files changed
tree: a1c70494539b8563b8256281697b1af0c7032ddc
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libunwind/
  16. lld/
  17. lldb/
  18. llvm/
  19. llvm-libgcc/
  20. mlir/
  21. offload/
  22. openmp/
  23. polly/
  24. pstl/
  25. runtimes/
  26. third-party/
  27. utils/
  28. .clang-format
  29. .clang-format-ignore
  30. .clang-tidy
  31. .git-blame-ignore-revs
  32. .gitattributes
  33. .gitignore
  34. .mailmap
  35. CODE_OF_CONDUCT.md
  36. CONTRIBUTING.md
  37. LICENSE.TXT
  38. pyproject.toml
  39. README.md
  40. SECURITY.md
README.md

The LLVM Compiler Infrastructure

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Welcome to the LLVM project!

This repository contains the source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The LLVM project has multiple components. The core of the project is itself called “LLVM”. This contains all of the tools, libraries, and header files needed to process intermediate representations and convert them into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer.

C-like languages use the Clang frontend. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

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