(Was: Re: [PATCH] wc: Add AVX2 optimization when counting only lines)
So, it looks like the check for avx2 support is broken - the build broke
for me after the update. Seems it is doing a compile check when a link
check is necessary.
I was seeing this in my build:
src/wc.c: In function 'avx2_supported':
src/wc.c:153:13: warning: implicit declaration of function
'__get_cpuid_count' [-Wimplicit-function-declaration]
if (! __get_cpuid_count (7, 0, &eax, &ebx, &ecx, &edx))
^
...
src/wc.o: In function `avx2_supported':
/.../coreutils/src/wc.c:153: undefined reference to `__get_cpuid_count'
collect2: error: ld returned 1 exit status
Makefile:9415: recipe for target 'src/wc' failed
My config.h has:
#define USE_AVX2_WC_LINECOUNT 1
My config.log has:
configure:77113: checking if __get_cpuid_count exists
configure:77129: gcc -c -g -O2 conftest.c >&5
conftest.c: In function 'main':
conftest.c:842:7: warning: implicit declaration of function
'__get_cpuid_count' [-Wimplicit-function-declaration]
__get_cpuid_count(7, 0, &eax, &ebx, &ecx, &edx);
^
configure:77129: $? = 0
configure:77131: result: yes
... So it looks like '__get_cpuid_count' not being declared is just
treated as a warning, and so the compile test succeeds. The actual
failure happens at link time. Would it be more appropriate to use
AC_LINK_IFELSE instead of AC_COMPILE_IFELSE ?
I tried swapping this out (as in the attached patch), and now it correctly
omits the #define for USE_AVX2_WC_LINECOUNT, and wc compiles & links
properly.