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I am trying to compile a C program using cmake which uses SIMD intrinsics. When I try to compile it, I get two errors

/usr/lib/gcc/x86_64-linux-gnu/5/include/smmintrin.h:326:1: error: inlining failed in call to always_inline ‘_mm_mullo_epi32’: target specific option mismatch _mm_mullo_epi32 (__m128i __X, __m128i __Y)

/usr/lib/gcc/x86_64-linux-gnu/5/include/tmmintrin.h:136:1: error: inlining failed in call to always_inline ‘_mm_shuffle_epi8’: target specific option mismatch _mm_shuffle_epi8 (__m128i __X, __m128i __Y)

This issue has already been solved here StackOverflow by setting 

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse4.1")

I try the very same and many other options. But my project still fails to compile. 

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse4.1") set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -sse4_1") set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=nehalem") set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse4.1 -msse4.2") set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=native") set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -ssse3")
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1

2 Answers 2

Reset to default
29

A general method to find the instruction switch for gcc

File intrin.sh:

#!/bin/bash get_instruction () { [ -z "$1" ] && exit func_name="$1[^1-9a-zA-Z_]" header_file=`grep --include=\*intrin.h -Rl "$func_name" /usr/lib/gcc | head -n1` [ -z "$header_file" ] && exit >&2 echo "found in: $header_file" target_directive=`grep "#pragma GCC target(\|$func_name" $header_file | grep -B 1 "$func_name" | head -n1` echo $target_directive | grep -o '"[^,]*[,"]' | sed 's/"//g' | sed 's/,//g' } instruction=`get_instruction $1` if [ -z "$instruction" ]; then echo "Error: function not found: $1" else echo "add this option to gcc: -m$instruction" fi

Usage:

./intrin.sh _mm_shuffle_epi8 # output: -mssse3 ./intrin.sh _mm_cvtepu8_epi32 # output: -msse4.1 ./intrin.sh _mm_loadu_ps # output: -msse ./intrin.sh _mm_clmulepi64_si128 # output: -mpclmul ./intrin.sh _mm256_loadu_si256 # output: -mavx ./intrin.sh _mm512_and_ps # output: -mavx512dq ./intrin.sh _mm_shl_epi8 # output: -mxop
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4 Comments

Note that it's usually a good idea to use something like -march=haswell, not just -mavx2 -mfma. Or at least add -mtune=znver2 (Zen 2) or something onto your -m ISA options. The "generic" tuning can be pretty poor for possibly-unaligned 256-bit vectors, especially when your data is usually aligned at runtime but the compiler just doesn't know that. See Why doesn't gcc resolve _mm256_loadu_pd as single vmovupd?. Or if you want to make a binary for your own machine, -march=native.
Excellent answer!
This wont work for some functions, like _mm_shl_epi8, as function definition in include file is directly followed by an opening parenthesis, and not a space. Possible fix: in get_instruction (), replace func_name="$1 " with func_name="$1[^[:alnum:]]".
@Bruno Thank you for the reminder, it has been corrected.
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Since you are compiling C code, not C++, you need:

set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -msse4.1")

You can get rid of all the other -march XXX and -msseXXX settings.

If you're using a mix of C and C++ then you could also add:

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse4.1")
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2 Comments

I had to add also -maes or ti did not work for me set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -msse4.1 -maes")
Or better, use -march=native if compiling for your own machine. That will enable everything your CPU has, and set tuning options.

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