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[CMake] Support per-target linker flags #68393

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merged 3 commits into from
Oct 17, 2023
Merged

[CMake] Support per-target linker flags #68393

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cc83200
[CMake] Support per-target linker flags
thevinster Oct 6, 2023
5decd59
fixup! [CMake] Support per-target linker flags
thevinster Oct 6, 2023
ac470a0
fixup! [CMake] Support per-target linker flags
thevinster Oct 16, 2023
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11 changes: 11 additions & 0 deletions llvm/cmake/modules/AddLLVM.cmake
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Original file line number Diff line number Diff line change
Expand Up @@ -726,6 +726,8 @@ function(llvm_add_library name)
endforeach()
endif()

add_custom_linker_flags(${name})

if(ARG_SHARED OR ARG_MODULE)
llvm_externalize_debuginfo(${name})
llvm_codesign(${name} ENTITLEMENTS ${ARG_ENTITLEMENTS} BUNDLE_PATH ${ARG_BUNDLE_PATH})
Expand Down Expand Up @@ -1019,6 +1021,8 @@ macro(add_llvm_executable name)
endforeach()
endif( LLVM_COMMON_DEPENDS )

add_custom_linker_flags(${name})

if(NOT ARG_IGNORE_EXTERNALIZE_DEBUGINFO)
llvm_externalize_debuginfo(${name})
endif()
Expand Down Expand Up @@ -1524,6 +1528,13 @@ macro(add_llvm_tool_subdirectory name)
add_llvm_external_project(${name})
endmacro(add_llvm_tool_subdirectory)

macro(add_custom_linker_flags name)
if (LLVM_${name}_LINKER_FLAGS)
message(STATUS "Applying ${LLVM_${name}_LINKER_FLAGS} to ${name}")
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I'd omit this to avoid the extra build spam (or make it optional).

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What did you mean by optional here? Like a CMake flag that enables the message? In general, I find this message to be quite helpful when debug whether targets were applied with custom flags without needing to go into the CMakeCache.txt.

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I'm going to land this as is, and if this becomes very build spammy, we can figure out other approaches to disable it.

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An alternative to an option would be to use the DEBUG mode instead of STATUS so developers can use CMAKE_MESSAGE_LOG_LEVEL to suppress the output if desired.

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#69497

target_link_options(${name} PRIVATE ${LLVM_${name}_LINKER_FLAGS})
endif()
endmacro()

function(get_project_name_from_src_var var output)
string(REGEX MATCH "LLVM_EXTERNAL_(.*)_SOURCE_DIR"
MACHED_TOOL "${var}")
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3 changes: 3 additions & 0 deletions llvm/docs/CMake.rst
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Expand Up @@ -428,6 +428,9 @@ enabled sub-projects. Nearly all of these variable names begin with
$CMAKE_INSTALL_PREFIX/Toolchains containing an xctoolchain directory which can
be used to override the default system tools.

**LLVM_<target>_LINKER_FLAGS**:STRING
Defines the set of linker flags that should be applied to a <target>.

**LLVM_DEFAULT_TARGET_TRIPLE**:STRING
LLVM target to use for code generation when no target is explicitly specified.
It defaults to "host", meaning that it shall pick the architecture
Expand Down