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[CMAKE] Enable FatLTO as a build option for LLVM #80480

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Merged
merged 4 commits into from
Mar 15, 2024
Merged

[CMAKE] Enable FatLTO as a build option for LLVM #80480

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c0f09d9
[CMAKE] Enable FatLTO as a build option for LLVM
ilovepi Aug 22, 2023
a2005ed
Add -ffat-lto-objects to CMAKE_C_FLAGS and CMAKE_CXX_FLAGS
ilovepi Feb 2, 2024
bce52e3
[cmake] Append -ffat-lto-objects to CMAKE_MODULE_LINKER_FLAGS
ilovepi Mar 5, 2024
10dceb4
Remove -fno-lto from COMPILE_FLAGS
ilovepi Mar 15, 2024
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1 change: 1 addition & 0 deletions clang/cmake/caches/Fuchsia-stage2.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ set(LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "

set(LLVM_ENABLE_BACKTRACES OFF CACHE BOOL "")
set(LLVM_ENABLE_DIA_SDK OFF CACHE BOOL "")
set(LLVM_ENABLE_FATLTO ON CACHE BOOL "")
set(LLVM_ENABLE_HTTPLIB ON CACHE BOOL "")
set(LLVM_ENABLE_LIBCXX ON CACHE BOOL "")
set(LLVM_ENABLE_LIBEDIT OFF CACHE BOOL "")
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10 changes: 8 additions & 2 deletions llvm/cmake/modules/AddLLVM.cmake
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Expand Up @@ -1637,8 +1637,14 @@ function(add_unittest test_suite test_name)
# The runtime benefits of LTO don't outweight the compile time costs for tests.
if(LLVM_ENABLE_LTO)
if((UNIX OR MINGW) AND LINKER_IS_LLD)
set_property(TARGET ${test_name} APPEND_STRING PROPERTY
LINK_FLAGS " -Wl,--lto-O0")
if(LLVM_ENABLE_FATLTO)
# When using FatLTO, just use relocatable linking.
set_property(TARGET ${test_name} APPEND_STRING PROPERTY
LINK_FLAGS " -Wl,--no-fat-lto-objects")
else()
set_property(TARGET ${test_name} APPEND_STRING PROPERTY
LINK_FLAGS " -Wl,--lto-O0")
endif()
elseif(LINKER_IS_LLD_LINK)
set_property(TARGET ${test_name} APPEND_STRING PROPERTY
LINK_FLAGS " /opt:lldlto=0")
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9 changes: 9 additions & 0 deletions llvm/cmake/modules/HandleLLVMOptions.cmake
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Expand Up @@ -32,6 +32,8 @@ endif()
set(LLVM_ENABLE_LTO OFF CACHE STRING "Build LLVM with LTO. May be specified as Thin or Full to use a particular kind of LTO")
string(TOUPPER "${LLVM_ENABLE_LTO}" uppercase_LLVM_ENABLE_LTO)

option(LLVM_ENABLE_FATLTO "Build LLVM with -ffat-lto-objects." OFF)

# Ninja Job Pool support
# The following only works with the Ninja generator in CMake >= 3.0.
set(LLVM_PARALLEL_COMPILE_JOBS "" CACHE STRING
Expand Down Expand Up @@ -1280,6 +1282,13 @@ elseif(LLVM_ENABLE_LTO)
endif()
endif()

if(LLVM_ENABLE_FATLTO AND (FUCHSIA OR UNIX))
append("-ffat-lto-objects" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
if(NOT LINKER_IS_LLD_LINK)
append("-ffat-lto-objects" CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS)
endif()
endif()

# Set an AIX default for LLVM_EXPORT_SYMBOLS_FOR_PLUGINS based on whether we are
# doing dynamic linking (see below).
set(LLVM_EXPORT_SYMBOLS_FOR_PLUGINS_AIX_default OFF)
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