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[CMake] Add a cache file for building a highly-optimized LLVM toolchain #117802

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[CMake] Add a cache file for building a highly-optimized LLVM toolchain #117802

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3bddb3c
[CMake] Add a cache file for building a highly-optimized LLVM toolchain
tstellar Sep 23, 2024
d188a03
Fix documentation
tstellar Nov 26, 2024
7d1bf4d
Use 3stages
tstellar Nov 27, 2024
ed2ba87
Update clang/cmake/caches/llvm-toolchain/stage1.cmake
tstellar Jan 9, 2025
3c26cba
Stage 1
tstellar Jan 10, 2025
3425cc6
stage2
tstellar Jan 10, 2025
bf3e961
Stage2-instrumented
tstellar Jan 10, 2025
5845f09
Add Module Linker flags
tstellar Jan 10, 2025
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13 changes: 13 additions & 0 deletions clang/cmake/caches/llvm-toolchain/stage1.cmake
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# Stage 1:
# * Build the prerequisites for stage 2.
# * We will be building an LTO optimized libcxx in stage 2, so we need to
# build clang and lld.


set(CMAKE_BUILD_TYPE Release CACHE STRING "")
set(LLVM_TARGETS_TO_BUILD Native CACHE STRING "")
set(LLVM_ENABLE_PROJECTS "clang;lld" CACHE STRING "")

set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")
set(CLANG_BOOTSTRAP_CMAKE_ARGS -C ${CMAKE_CURRENT_LIST_DIR}/stage2.cmake CACHE BOOL "")
set(CLANG_BOOTSTRAP_TARGETS stage3-check-all stage3-distribution stage3-install-distribution stage3-clang stage3-clang-bolt CACHE BOOL "")
20 changes: 20 additions & 0 deletions clang/cmake/caches/llvm-toolchain/stage2.cmake
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# Stage 2:
# * Build an LTO optimized libcxx, so we can staticially link it into stage 3
# clang.
# * Stage 3 will be PGO optimized, so we need to build clang, lld, and
# compiler-rt in stage 2.


set(CMAKE_BUILD_TYPE Release CACHE STRING "")
set(LLVM_TARGETS_TO_BUILD Native CACHE STRING "")
set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "" FORCE)
set(LLVM_ENABLE_PROJECTS "clang;lld" CACHE STRING "" FORCE)

set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")
set(CLANG_BOOTSTRAP_CMAKE_ARGS -C ${CMAKE_CURRENT_LIST_DIR}/stage3-instrumented.cmake CACHE BOOL "")
set(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED IR CACHE BOOL "")
set(CLANG_BOOTSTRAP_TARGETS stage3-check-all stage3-distribution stage3-install-distribution stage3-clang stage3-clang-bolt CACHE BOOL "")
set(LIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY ON CACHE STRING "")
set(RUNTIMES_CMAKE_ARGS "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON" CACHE STRING "")
set(LLVM_ENABLE_LLD ON CACHE STRING "")
#set(CLANG_DEFAULT_RTLIB compiler-rt CACHE STRING "")
10 changes: 10 additions & 0 deletions clang/cmake/caches/llvm-toolchain/stage3-instrumented.cmake
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# Stage 3 instrumented:
# * Build an instrumented clang, so we can generate profile data for stage 3.


set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")
set(CLANG_BOOTSTRAP_CMAKE_ARGS -C ${CMAKE_CURRENT_LIST_DIR}/stage3.cmake CACHE BOOL "")
set(CLANG_BOOTSTRAP_TARGETS clang check-all distribution install-distribution clang-bolt CACHE BOOL "")
set(CLANG_BOLT OFF CACHE STRING "")

include(${CMAKE_CURRENT_LIST_DIR}/stage3.cmake)
16 changes: 16 additions & 0 deletions clang/cmake/caches/llvm-toolchain/stage3.cmake
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# Stage 3:
# * This is the final stage.
# * The goals is to have a clang that is LTO, PGO, and bolt optimized and also
# statically linked to libcxx and compiler-rt.

set(LLVM_TARGETS_TO_BUILD Native CACHE STRING "")
set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "" FORCE)
set(LLVM_ENABLE_PROJECTS "clang;lld;bolt;" CACHE STRING "" FORCE)
set(LLVM_ENABLE_LLD ON CACHE STRING "")
set(LLVM_ENABLE_LTO THIN CACHE STRING "")
set(LLVM_ENABLE_LIBCXX ON CACHE STRING "")
set(LLVM_STATIC_LINK_CXX_STDLIB ON CACHE STRING "")
set(CLANG_BOLT "INSTRUMENT" CACHE STRING "")
set(CMAKE_EXE_LINKER_FLAGS "-Wl,--emit-relocs,-znow -rtlib=compiler-rt --unwindlib=libunwind -static-libgcc" CACHE STRING "")
set(CMAKE_SHARED_LINKER_FLAGS "-rtlib=compiler-rt --unwindlib=libunwind -static-libgcc" CACHE STRING "")
set(LLVM_DISTRIBUTION_COMPONENTS "clang;lld;runtimes;clang-resource-headers" CACHE STRING "")
21 changes: 21 additions & 0 deletions clang/cmake/caches/llvm-toolchain/usage.rst
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# LLVM Toolchain Build

This directory contains cache files for building a complete LLVM-based toolchain.
The resulting clang build will be LTO, PGO, and BOLT optimized and statically
linked against libc++ and compiler-rt.

The build is done in 4 stages:

* Stage 1: Build clang/lld.
* Stage 2: Build an LTO optimized libc++ with Stage 1 clang/lld.
* Stage 3 Instrumented: Build clang with instrumentation in order to generate
profile data for PGO.
* Stage 3: Build clang with LTO, PGO, and BOLT optimizations and statically link
with stage2 libc++ and compiler-rt.

## Usage

::

$ cmake -S llvm -B build -C clang/cmake/caches/llvm-toolchain/stage1.cmake
$ ninja stage3-install-distribution