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CMake: Autodetect unaligned access support on LoongArch

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This still relies on CMAKE_SYSTEM_PROCESSOR. CMake 4.1 added more
CMAKE_<LANG>_COMPILER_ARCHITECTURE_ID values to detect the arch in
a more defined manner, but 4.1 is too new to require for now.

Thanks-to: Li Chenggang <lichenggang@deepin.org>
Closes: https://github.com/tukaani-project/xz/pull/186
This commit is contained in:
Lasse Collin 2025-12-09 12:13:36 +02:00
parent 7971566247
commit 1ec43aa781
No known key found for this signature in database
GPG Key ID: 38EE757D69184620
1 changed files with 81 additions and 0 deletions
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81
cmake/tuklib_integer.cmake
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@ -14,6 +14,69 @@ include(CheckCSourceCompiles)
include(CheckIncludeFile)
include(CheckSymbolExists)
# An internal helper for tuklib_integer that attempts to detect if
# -mstrict-align or -mno-strict-align is in effect. This sets the
# cache variable TUKLIB_INTEGER_STRICT_ALIGN to ON if OBJDUMP_REGEX
# matches the objdump output of a check program. Otherwise it is set to OFF.
function(tuklib_integer_internal_strict_align OBJDUMP_REGEX)
if(NOT DEFINED TUKLIB_INTEGER_STRICT_ALIGN)
# Build a static library because then the function won't be optimized
# away, and there won't be any unrelated startup code either.
set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
# CMake >= 3.25 wouldn't require us to create a temporary file,
# but the following method is compatible with 3.20.
file(WRITE "${CMAKE_BINARY_DIR}/tuklib_integer_strict_align.c" "
#include <string.h>
unsigned int check_strict_align(const void *p)
{
unsigned int i;
memcpy(&i, p, sizeof(i));
return i;
}
")
# Force -O2 because memcpy() won't be optimized out if optimizations
# are disabled.
try_compile(
TRY_COMPILE_RESULT
"${CMAKE_BINARY_DIR}"
"${CMAKE_BINARY_DIR}/tuklib_integer_strict_align.c"
COMPILE_DEFINITIONS "${CMAKE_REQUIRED_DEFINITIONS}"
CMAKE_FLAGS "-DCOMPILE_DEFINITIONS=${CMAKE_REQUIRED_FLAGS} -O2"
COPY_FILE "${CMAKE_BINARY_DIR}/tuklib_integer_strict_align.a"
)
if(NOT TRY_COMPILE_RESULT)
message(FATAL_ERROR
"Compilation of the strict align check failed. "
"Either the specified compiler flags are broken "
"or ${CMAKE_CURRENT_FUNCTION_LIST_FILE} has a bug.")
endif()
# Use WORKING_DIRECTORY instead of passing the full path to objdump.
# This ensures that the pathname won't affect the objdump output,
# which could result in an unwanted regex match in the next step.
execute_process(
COMMAND "${CMAKE_OBJDUMP}" -d "tuklib_integer_strict_align.a"
WORKING_DIRECTORY "${CMAKE_BINARY_DIR}"
OUTPUT_VARIABLE OBJDUMP_OUTPUT
RESULT_VARIABLE OBJDUMP_RESULT
)
# FIXME? Should we remove the temporary files here?
# Look for instructions that load unsigned bytes. If none are found,
# assume that -mno-strict-align is in effect.
if(OBJDUMP_RESULT STREQUAL "0" AND
OBJDUMP_OUTPUT MATCHES "${OBJDUMP_REGEX}")
set(TUKLIB_INTEGER_STRICT_ALIGN ON CACHE INTERNAL "")
else()
set(TUKLIB_INTEGER_STRICT_ALIGN OFF CACHE INTERNAL "")
endif()
endif()
endfunction()
function(tuklib_integer TARGET_OR_ALL)
# Check for endianness. Unlike the Autoconf's AC_C_BIGENDIAN, this doesn't
# support Apple universal binaries. The CMake module will leave the
@ -64,10 +127,22 @@ function(tuklib_integer TARGET_OR_ALL)
# - 32/64-bit x86 / x86-64
# - 32/64-bit big endian PowerPC
# - 64-bit little endian PowerPC
# - 32/64-bit Loongarch (*)
# - Some 32-bit ARM
# - Some 64-bit ARM64 (AArch64)
# - Some 32/64-bit RISC-V
#
# (*) See sections 7.4, 8.1, and 8.2:
# https://github.com/loongson/la-softdev-convention/blob/v0.2/la-softdev-convention.adoc
#
# That is, desktop and server processors likely support
# unaligned access in hardware but embedded processors
# might not. GCC defaults to -mno-strict-align and so
# do majority of GNU/Linux distributions. As of
# GCC 15.2, there is no predefined macro to detect
# if -mstrict-align or -mno-strict-align is in effect.
# We use heuristics based on compiler output.
#
# CMake doesn't provide a standardized/normalized list of processor arch
# names. For example, x86-64 may be "x86_64" (Linux), "AMD64" (Windows),
# or even "EM64T" (64-bit WinXP).
@ -116,6 +191,12 @@ function(tuklib_integer TARGET_OR_ALL)
if(TUKLIB_FAST_UNALIGNED_DEFINED_BY_PREPROCESSOR)
set(FAST_UNALIGNED_GUESS ON)
endif()
elseif(PROCESSOR MATCHES "^loongarch")
tuklib_integer_internal_strict_align("[ \t]ld\\.bu[ \t]")
if(NOT TUKLIB_INTEGER_STRICT_ALIGN)
set(FAST_UNALIGNED_GUESS ON)
endif()
endif()
option(TUKLIB_FAST_UNALIGNED_ACCESS