cyb70289 commented on code in PR #14515:
URL: https://github.com/apache/arrow/pull/14515#discussion_r1005763894
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cpp/cmake_modules/SetupCxxFlags.cmake:
##########
@@ -496,14 +494,24 @@ if(ARROW_CPU_FLAG STREQUAL "armv8")
endif()
set(CXX_COMMON_FLAGS "${CXX_COMMON_FLAGS} ${ARROW_ARMV8_ARCH_FLAG}")
+ set(ARROW_HAVE_NEON ON)
add_definitions(-DARROW_HAVE_NEON)
- if(ARROW_ARMV8_ARCH_FLAG MATCHES "\\+crypto")
- add_definitions(-DARROW_HAVE_ARMV8_CRYPTO)
- endif()
- # armv8.1+ implies crc support
- if(ARROW_ARMV8_ARCH_FLAG MATCHES "armv8\\.[1-9]|\\+crc")
- add_definitions(-DARROW_HAVE_ARMV8_CRC)
+ if(ARROW_SIMD_LEVEL MATCHES "SVE[0-9]*")
+ if(NOT ARROW_ARMV8_ARCH_FLAG MATCHES "\\+sve")
+ message(FATAL_ERROR "SIMD Level is set to ${ARROW_SIMD_LEVEL} but SVE
is not enabled in compiler options. "
+ "Add \"-DARROW_ARMV8_ARCH=armv8-a+sve\" to cmake
command line to enable SVE."
Review Comment:
I'm thinking about removing this cmake option `ARROW_ARMV8_ARCH`, and use
only `ARROW_SIMD_LEVEL`.
https://github.com/apache/arrow/blob/master/cpp/cmake_modules/DefineOptions.cmake#L204
`ARROW_ARMV8_ARCH` is append to `gcc -march=???`, it's only for Arm. x86
doesn't need `-march` as x86 has compiler options for each feature, e.g.,
`-msse4.2`, `-mavx2`, etc, to enable specific SIMD instructions.
But Arm doesn't have these compiler options, CPU features are set by
`-march` only, e.g., `-march=armv8-a+sve`, `-march=armv8.2-a+crypto`, etc.
Specify `-march` by cmake command line gives more flexibility, but looks
most of the time it also introduces unnecessary complexity.
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