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[CMake][Release] Statically link clang with stage1 runtimes #127268

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Merged
merged 12 commits into from
Feb 20, 2025
Merged

[CMake][Release] Statically link clang with stage1 runtimes #127268

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a705acf
[CMake][Release] Statically link clang with stage1 runtimes
tstellar Feb 14, 2025
c568022
Fix linker usage
tstellar Feb 15, 2025
88e8ad4
flang: Fix build with latest libc++
tstellar Feb 15, 2025
92d6389
Fix typo in flang fix
tstellar Feb 15, 2025
8ddc8a9
Drop -static-libgcc option on Darwin
tstellar Feb 15, 2025
9701c52
flang fix
tstellar Feb 15, 2025
ff19330
Better fix
tstellar Feb 17, 2025
73460af
Merge remote-tracking branch 'origin/main' into HEAD
tstellar Feb 17, 2025
cd61d6e
Fix formatting
tstellar Feb 17, 2025
b2a3e82
Merge branch 'main' into release-static
tstellar Feb 19, 2025
9cc8223
Document why we can't use LLVM_ENABLE_LTO
tstellar Feb 20, 2025
345092f
Update comments
tstellar Feb 20, 2025
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27 changes: 23 additions & 4 deletions clang/cmake/caches/Release.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -48,10 +48,8 @@ set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")

set(STAGE1_PROJECTS "clang")

# Building Flang on Windows requires compiler-rt, so we need to build it in
# stage1. compiler-rt is also required for building the Flang tests on
# macOS.
set(STAGE1_RUNTIMES "compiler-rt")
# Build all runtimes so we can statically link them into the stage2 compiler.
set(STAGE1_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind")

if (LLVM_RELEASE_ENABLE_PGO)
list(APPEND STAGE1_PROJECTS "lld")
Expand Down Expand Up @@ -90,9 +88,20 @@ else()
set(CLANG_BOOTSTRAP_TARGETS ${LLVM_RELEASE_FINAL_STAGE_TARGETS} CACHE STRING "")
endif()

if (LLVM_RELEASE_ENABLE_LTO)
# Enable LTO for the runtimes. We need to configure stage1 clang to default
# to using lld as the linker because the stage1 toolchain will be used to
# build and link the runtimes.
# FIXME: We can't use LLVM_ENABLE_LTO=Thin here, because it causes the CMake
# step for the libcxx build to fail. CMAKE_INTERPROCEDURAL_OPTIMIZATION does
# enable ThinLTO, though.
set(RUNTIMES_CMAKE_ARGS "-DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON -DLLVM_ENABLE_LLD=ON" CACHE STRING "")
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Is there a reason we can't use LLVM_ENABLE_LTO=Thin here? It would be more explicit that we enable ThinLTO over whatever CMake deems good in that case.

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LLVM_ENABLE_LTO=Thin causes some of the CMake checks for the runtime build to fail which fails the whole build. -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON does enable ThinLTO, so it's effectively the same.

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That's odd. Maybe we could at least say why we are not using that flag there since that's the one that's documented in the llvm documentation.

endif()

# Stage 1 Common Config
set(LLVM_ENABLE_RUNTIMES ${STAGE1_RUNTIMES} CACHE STRING "")
set(LLVM_ENABLE_PROJECTS ${STAGE1_PROJECTS} CACHE STRING "")
set(LIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY ON CACHE STRING "")

# stage2-instrumented and Final Stage Config:
# Options that need to be set in both the instrumented stage (if we are doing
Expand All @@ -102,6 +111,16 @@ set_instrument_and_final_stage_var(LLVM_ENABLE_LTO "${LLVM_RELEASE_ENABLE_LTO}"
if (LLVM_RELEASE_ENABLE_LTO)
set_instrument_and_final_stage_var(LLVM_ENABLE_LLD "ON" BOOL)
endif()
set_instrument_and_final_stage_var(LLVM_ENABLE_LIBCXX "ON" BOOL)
set_instrument_and_final_stage_var(LLVM_STATIC_LINK_CXX_STDLIB "ON" BOOL)
set(RELEASE_LINKER_FLAGS "-rtlib=compiler-rt --unwindlib=libunwind")
if(NOT ${CMAKE_HOST_SYSTEM_NAME} MATCHES "Darwin")
set(RELEASE_LINKER_FLAGS "${RELEASE_LINKER_FLAGS} -static-libgcc")
endif()

set_instrument_and_final_stage_var(CMAKE_EXE_LINKER_FLAGS ${RELEASE_LINKER_FLAGS} STRING)
set_instrument_and_final_stage_var(CMAKE_SHARED_LINKER_FLAGS ${RELEASE_LINKER_FLAGS} STRING)
set_instrument_and_final_stage_var(CMAKE_MODULE_LINKER_FLAGS ${RELEASE_LINKER_FLAGS} STRING)

# Final Stage Config (stage2)
set_final_stage_var(LLVM_ENABLE_RUNTIMES "${LLVM_RELEASE_ENABLE_RUNTIMES}" STRING)
Expand Down
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