this is a shame, the pragma option seemed super clean if clang worked with
it. ad hoc library seems like a close second given we can't change CFLAGS
without changing the whole repo
On Sat, Dec 21, 2024, 23:14 Bruno Haible <br...@clisp.org> wrote:
> The gnulib CIs also exercise compilation with clang, and it failed today:
>
> clang -DHAVE_CONFIG_H -I. -I../../gllib -I.. -DGNULIB_STRICT_CHECKING=1
> -I/media/develdata/devel/inst-x86_64-64/include -Wall -g -O2 -MT
> crc-x86_64-pclmul.o -MD -MP -MF .deps/crc-x86_64-pclmul.Tpo -c -o
> crc-x86_64-pclmul.o ../../gllib/crc-x86_64-pclmul.c
> ../../gllib/crc-x86_64-pclmul.c:27:13: warning: unknown pragma ignored
> [-Wunknown-pragmas]
> #pragma GCC push_options
> ^
> ../../gllib/crc-x86_64-pclmul.c:28:13: warning: unknown pragma ignored
> [-Wunknown-pragmas]
> #pragma GCC target("pclmul,avx")
> ^
> ../../gllib/crc-x86_64-pclmul.c:208:13: warning: unknown pragma ignored
> [-Wunknown-pragmas]
> #pragma GCC pop_options
> ^
> ../../gllib/crc-x86_64-pclmul.c:83:16: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_high = _mm_clmulepi64_si128 (in1, shift544_shift480, 0x11);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:84:15: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_low = _mm_clmulepi64_si128 (in1, shift544_shift480, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:87:16: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_high = _mm_clmulepi64_si128 (in2, shift544_shift480, 0x11);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:88:15: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_low = _mm_clmulepi64_si128 (in2, shift544_shift480, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:91:16: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_high = _mm_clmulepi64_si128 (in3, shift544_shift480, 0x11);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:92:15: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_low = _mm_clmulepi64_si128 (in3, shift544_shift480, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:95:16: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_high = _mm_clmulepi64_si128 (in4, shift544_shift480, 0x11);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:96:15: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_low = _mm_clmulepi64_si128 (in4, shift544_shift480, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:133:19: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_high = _mm_clmulepi64_si128 (in1, shift160_shift96, 0x11);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:134:18: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_low = _mm_clmulepi64_si128 (in1, shift160_shift96, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:164:19: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_high = _mm_clmulepi64_si128 (in1, shift160_shift96, 0x11);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:165:18: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> fold_low = _mm_clmulepi64_si128 (in1, shift160_shift96, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:180:9: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> in1 = _mm_clmulepi64_si128 (shift96_shift64, in1, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:187:9: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> in1 = _mm_clmulepi64_si128 (shift96_shift64, in2, 0x01);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:194:9: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> in2 = _mm_clmulepi64_si128 (mu_poly, in2, 0x00);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> ../../gllib/crc-x86_64-pclmul.c:198:9: error:
> '__builtin_ia32_pclmulqdq128' needs target feature pclmul
> in2 = _mm_clmulepi64_si128 (mu_poly, in2, 0x01);
> ^
> /clang/14.0.0/include/__wmmintrin_pclmul.h:45:13: note: expanded from
> macro '_mm_clmulepi64_si128'
> ((__m128i)__builtin_ia32_pclmulqdq128((__v2di)(__m128i)(X), \
> ^
> 3 warnings and 16 errors generated.
> make[3]: *** [Makefile:1123: crc-x86_64-pclmul.o] Error 1
>
>
> This is reproducible with clang versions 7 to 19 (the newest one), for
> example
> in a testdir:
>
> $ ./gnulib-tool --create-testdir --dir=../testdir1 --single-configure
> crc crc-x86_64
>
> The reason is that clang does not support the '#pragma GCC target(...)'.
>
>
> Three approaches to fix this are possible:
>
> a) As suggested by Simon in
> <https://lists.gnu.org/archive/html/bug-gnulib/2024-12/msg00112.html>:
> Use the '#pragma GCC target(...)' also in configure.ac.
> Drawback: This means to disable the optimization when clang is used to
> build the package.
>
> b) Use the per-object flag syntax from
>
> https://www.gnu.org/software/make/manual/html_node/Target_002dspecific.html
> :
>
> crc-x86_64-pclmul.o: CFLAGS += -mavx -mpclmul
>
> Drawback: This works with GNU make, FreeBSD make, NetBSD make, but not
> with
> OpenBSD make.
>
> c) Use an ad-hoc library in the Makefile. This is well supported in
> Automake
> and thus does not cause portability problems.
> Drawback: It requires changes in gnulib-tool.
>
> I picked approach c), and committed the two attached patches. Tested both
> without libtool (in a testdir) and with libtool (in some package that uses
> gnulib for some shared library).
>
>
> 2024-12-21 Bruno Haible <br...@clisp.org>
>
> crc-x86_64: Fix compilation error with clang.
> * modules/crc-x86_64 (Makefile.am): Declare a separate library
> libpclmul.{a,la}.
> * lib/crc-x86_64-pclmul.c: Remove the GCC pragmas.
>
> gnulib-tool: Recognize @LT@, @la@, @lo@ tokens in module
> descriptions.
> * gnulib-tool.sh (func_emit_lib_Makefile_am): Replace @LT@, @la@,
> @lo@
> tokens.
> (func_emit_tests_Makefile_am): Likewise.
> * pygnulib/GLEmiter.py (GLEmiter.lib_Makefile_am): Likewise.
> (GLEmiter.tests_Makefile_am): Likewise.
>
>
