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# ------------------------------------------------------------------------------
# Cpu features definition and flags
# ------------------------------------------------------------------------------
if(${LIBC_TARGET_MACHINE} MATCHES "x86|x86_64")
set(ALL_CPU_FEATURES SSE SSE2 AVX AVX2 AVX512F)
list(SORT ALL_CPU_FEATURES)
endif()
# Function to check whether the host supports the provided set of features.
# Usage:
# host_supports(
# <output variable>
# <list of cpu features>
# )
function(host_supports output_var features)
_intersection(a "${HOST_CPU_FEATURES}" "${features}")
if("${a}" STREQUAL "${features}")
set(${output_var} TRUE PARENT_SCOPE)
else()
unset(${output_var} PARENT_SCOPE)
endif()
endfunction()
# Function to compute the flags to pass down to the compiler.
# Usage:
# compute_flags(
# <output variable>
# MARCH <arch name or "native">
# REQUIRE <list of mandatory features to enable>
# REJECT <list of features to disable>
# )
function(compute_flags output_var)
cmake_parse_arguments(
"COMPUTE_FLAGS"
"" # Optional arguments
"MARCH" # Single value arguments
"REQUIRE;REJECT" # Multi value arguments
${ARGN})
# Check that features are not required and rejected at the same time.
if(COMPUTE_FLAGS_REQUIRE AND COMPUTE_FLAGS_REJECT)
_intersection(var ${COMPUTE_FLAGS_REQUIRE} ${COMPUTE_FLAGS_REJECT})
if(var)
message(FATAL_ERROR "Cpu Features REQUIRE and REJECT ${var}")
endif()
endif()
# Generate the compiler flags in `current`.
if(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang|GNU")
if(COMPUTE_FLAGS_MARCH)
list(APPEND current "-march=${COMPUTE_FLAGS_MARCH}")
endif()
foreach(feature IN LISTS COMPUTE_FLAGS_REQUIRE)
string(TOLOWER ${feature} lowercase_feature)
list(APPEND current "-m${lowercase_feature}")
endforeach()
foreach(feature IN LISTS COMPUTE_FLAGS_REJECT)
string(TOLOWER ${feature} lowercase_feature)
list(APPEND current "-mno-${lowercase_feature}")
endforeach()
else()
# In future, we can extend for other compilers.
message(FATAL_ERROR "Unkown compiler ${CMAKE_CXX_COMPILER_ID}.")
endif()
# Export the list of flags.
set(${output_var} "${current}" PARENT_SCOPE)
endfunction()
# ------------------------------------------------------------------------------
# Internal helpers and utilities.
# ------------------------------------------------------------------------------
# Computes the intersection between two lists.
function(_intersection output_var list1 list2)
foreach(element IN LISTS list1)
if("${list2}" MATCHES "(^|;)${element}(;|$)")
list(APPEND tmp "${element}")
endif()
endforeach()
set(${output_var} ${tmp} PARENT_SCOPE)
endfunction()
# Generates a cpp file to introspect the compiler defined flags.
function(_generate_check_code)
foreach(feature IN LISTS ALL_CPU_FEATURES)
set(DEFINITIONS
"${DEFINITIONS}
#ifdef __${feature}__
\"${feature}\",
#endif")
endforeach()
configure_file(
"${LIBC_SOURCE_DIR}/cmake/modules/cpu_features/check_cpu_features.cpp.in"
"cpu_features/check_cpu_features.cpp" @ONLY)
endfunction()
_generate_check_code()
# Compiles and runs the code generated above with the specified requirements.
# This is helpful to infer which features a particular target supports or if
# a specific features implies other features (e.g. BMI2 implies SSE2 and SSE).
function(_check_defined_cpu_feature output_var)
cmake_parse_arguments(
"CHECK_DEFINED"
"" # Optional arguments
"MARCH" # Single value arguments
"REQUIRE;REJECT" # Multi value arguments
${ARGN})
compute_flags(
flags
MARCH ${CHECK_DEFINED_MARCH}
REQUIRE ${CHECK_DEFINED_REQUIRE}
REJECT ${CHECK_DEFINED_REJECT})
try_run(
run_result compile_result "${CMAKE_CURRENT_BINARY_DIR}/check_${feature}"
"${CMAKE_CURRENT_BINARY_DIR}/cpu_features/check_cpu_features.cpp"
COMPILE_DEFINITIONS ${flags}
COMPILE_OUTPUT_VARIABLE compile_output
RUN_OUTPUT_VARIABLE run_output)
if(${compile_result} AND ("${run_result}" EQUAL 0))
set(${output_var}
"${run_output}"
PARENT_SCOPE)
else()
message(FATAL_ERROR "${compile_output}")
endif()
endfunction()
# Populates the HOST_CPU_FEATURES list.
# Use -march=native only when the compiler supports it.
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-march=native" COMPILER_SUPPORTS_MARCH_NATIVE)
if(COMPILER_SUPPORTS_MARCH_NATIVE)
_check_defined_cpu_feature(HOST_CPU_FEATURES MARCH native)
else()
_check_defined_cpu_feature(HOST_CPU_FEATURES)
endif()
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