[libc-commits] [libc] [libc] [startup] add cmake function to merge separated crt1 objects (PR #75413)
Schrodinger ZHU Yifan via libc-commits
libc-commits at lists.llvm.org
Thu Dec 14 13:21:25 PST 2023
https://github.com/SchrodingerZhu updated https://github.com/llvm/llvm-project/pull/75413
>From d76bb7ff45ab0aa687b4ec9ddc51f88e95c5d0dc Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Wed, 13 Dec 2023 19:16:34 -0500
Subject: [PATCH 1/4] [libc] [startup] add cmake function to merge separated
crt1 objects
As part of startup refactoring, this patch adds a function to merge multiple objects into a single relocatable object:
cc -r obj1.o obj2.o -o obj.o
A relocatable object is an object file that is not fully linked into an executable or a shared library. It is an intermediate file format that can be passed into the linker.
A crt object can have arch-specific code and arch-agnostic code. To reduce code cohesion, the implementation is splitted into multiple units. As a result, we need to merge them into a single relocatable object.
---
libc/startup/linux/CMakeLists.txt | 46 ++++++++++++++++++++++++++++---
1 file changed, 42 insertions(+), 4 deletions(-)
diff --git a/libc/startup/linux/CMakeLists.txt b/libc/startup/linux/CMakeLists.txt
index 007aa30c17d6ab..5ca5010f6b1fe4 100644
--- a/libc/startup/linux/CMakeLists.txt
+++ b/libc/startup/linux/CMakeLists.txt
@@ -1,3 +1,42 @@
+# This function merges multiple objects into a single relocatable object
+# cc -r obj1.o obj2.o -o obj.o
+# A relocatable object is an object file that is not fully linked into an
+# executable or a shared library. It is an intermediate file format that can
+# be passed into the linker.
+# A crt object have arch-specific code and arch-agnostic code. To reduce code
+# cohesion, the implementation is splitted into multiple units. As a result,
+# we need to merge them into a single relocatable object.
+function(merge_relocatable_object name)
+ set(obj_list "")
+ set(fq_link_libraries "")
+ get_fq_deps_list(fq_dep_list ${ARGN})
+ foreach(target IN LISTS fq_dep_list)
+ list(APPEND obj_list "$<TARGET_OBJECTS:${target}>")
+ get_target_property(libs ${target} DEPS)
+ list(APPEND fq_link_libraries "${libs}")
+ endforeach()
+ get_fq_target_name(${name} fq_name)
+ add_custom_command(
+ OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
+ COMMAND ${CMAKE_CXX_COMPILER} -r ${obj_list} -o ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
+ DEPENDS ${obj_list}
+ COMMAND_EXPAND_LISTS
+ )
+ add_custom_target(${fq_name}.relocatable DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${name}.o)
+ add_library(${fq_name} OBJECT IMPORTED GLOBAL)
+ add_dependencies(${fq_name} ${fq_name}.relocatable)
+ target_link_libraries(${fq_name} INTERFACE ${fq_link_libraries})
+ set_target_properties(
+ ${fq_name}
+ PROPERTIES
+ LINKER_LANGUAGE CXX
+ OBJECT_FILES ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
+ IMPORTED_OBJECTS ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
+ TARGET_TYPE ${OBJECT_LIBRARY_TARGET_TYPE}
+ DEPS "${fq_link_libraries}"
+ )
+endfunction()
+
function(add_startup_object name)
cmake_parse_arguments(
"ADD_STARTUP_OBJECT"
@@ -34,11 +73,10 @@ endif()
add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
-add_startup_object(
+# TODO: factor out crt1 into multiple objects
+merge_relocatable_object(
crt1
- ALIAS
- DEPENDS
- .${LIBC_TARGET_ARCHITECTURE}.crt1
+ .${LIBC_TARGET_ARCHITECTURE}.crt1
)
add_startup_object(
>From b122d1bc22db6e220bab58ac7d50d6f06602837a Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Wed, 13 Dec 2023 19:20:38 -0500
Subject: [PATCH 2/4] fix typo
---
libc/startup/linux/CMakeLists.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libc/startup/linux/CMakeLists.txt b/libc/startup/linux/CMakeLists.txt
index 5ca5010f6b1fe4..33bd18e4f126a8 100644
--- a/libc/startup/linux/CMakeLists.txt
+++ b/libc/startup/linux/CMakeLists.txt
@@ -3,7 +3,7 @@
# A relocatable object is an object file that is not fully linked into an
# executable or a shared library. It is an intermediate file format that can
# be passed into the linker.
-# A crt object have arch-specific code and arch-agnostic code. To reduce code
+# A crt object has arch-specific code and arch-agnostic code. To reduce code
# cohesion, the implementation is splitted into multiple units. As a result,
# we need to merge them into a single relocatable object.
function(merge_relocatable_object name)
>From 644b22993f3a1c04f783aee03046bf915c18ff09 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Wed, 13 Dec 2023 19:22:38 -0500
Subject: [PATCH 3/4] remove alias related code
---
libc/startup/linux/CMakeLists.txt | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/libc/startup/linux/CMakeLists.txt b/libc/startup/linux/CMakeLists.txt
index 33bd18e4f126a8..52b677b49137d8 100644
--- a/libc/startup/linux/CMakeLists.txt
+++ b/libc/startup/linux/CMakeLists.txt
@@ -40,19 +40,14 @@ endfunction()
function(add_startup_object name)
cmake_parse_arguments(
"ADD_STARTUP_OBJECT"
- "ALIAS" # Option argument
+ "" # Option argument
"SRC" # Single value arguments
"DEPENDS;COMPILE_OPTIONS" # Multi value arguments
${ARGN}
)
get_fq_target_name(${name} fq_target_name)
- if(ADD_STARTUP_OBJECT_ALIAS)
- get_fq_deps_list(fq_dep_list ${ADD_STARTUP_OBJECT_DEPENDS})
- add_library(${fq_target_name} ALIAS ${fq_dep_list})
- return()
- endif()
-
+
add_object_library(
${name}
SRCS ${ADD_STARTUP_OBJECT_SRC}
>From 8028db1f56a9783971dda863525d456f5acc98d8 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Thu, 14 Dec 2023 16:21:10 -0500
Subject: [PATCH 4/4] use dd_executable instead
---
libc/startup/linux/CMakeLists.txt | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/libc/startup/linux/CMakeLists.txt b/libc/startup/linux/CMakeLists.txt
index 52b677b49137d8..b89eacbf346928 100644
--- a/libc/startup/linux/CMakeLists.txt
+++ b/libc/startup/linux/CMakeLists.txt
@@ -15,14 +15,26 @@ function(merge_relocatable_object name)
get_target_property(libs ${target} DEPS)
list(APPEND fq_link_libraries "${libs}")
endforeach()
+ list(REMOVE_DUPLICATES obj_list)
+ list(REMOVE_DUPLICATES fq_link_libraries)
get_fq_target_name(${name} fq_name)
- add_custom_command(
- OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
- COMMAND ${CMAKE_CXX_COMPILER} -r ${obj_list} -o ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
- DEPENDS ${obj_list}
- COMMAND_EXPAND_LISTS
+ add_executable(
+ ${fq_name}.relocatable
+ ${obj_list}
+ )
+ target_link_options(
+ ${fq_name}.relocatable
+ PRIVATE
+ -nostdlib
+ -ffreestanding
+ -no-pie
+ -nostartfiles
+ -Wl,-r)
+ set_target_properties(
+ ${fq_name}.relocatable
+ PROPERTIES
+ OUTPUT_NAME ${name}.o
)
- add_custom_target(${fq_name}.relocatable DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${name}.o)
add_library(${fq_name} OBJECT IMPORTED GLOBAL)
add_dependencies(${fq_name} ${fq_name}.relocatable)
target_link_libraries(${fq_name} INTERFACE ${fq_link_libraries})
@@ -30,7 +42,6 @@ function(merge_relocatable_object name)
${fq_name}
PROPERTIES
LINKER_LANGUAGE CXX
- OBJECT_FILES ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
IMPORTED_OBJECTS ${CMAKE_CURRENT_BINARY_DIR}/${name}.o
TARGET_TYPE ${OBJECT_LIBRARY_TARGET_TYPE}
DEPS "${fq_link_libraries}"
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