Re: [PATCH] Fix PR81921

[Uros Bizjak <ubizjak at gmail dot com>]

On Wed, Aug 23, 2017 at 11:40 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
> On Wed, Aug 23, 2017 at 11:22 AM, Richard Biener <rguenther@suse.de> wrote:
>>> >  /* If the machine does not have a case insn that compares the bounds,
>>> > Index: gcc/config/i386/i386.c
>>> > ===================================================================
>>> > --- gcc/config/i386/i386.c      (revision 251275)
>>> > +++ gcc/config/i386/i386.c      (working copy)
>>> > @@ -7369,7 +7369,8 @@ ix86_valid_target_attribute_tree (tree a
>>> >        || opts->x_target_flags != def->x_target_flags
>>> >        || option_strings[IX86_FUNCTION_SPECIFIC_ARCH]
>>> >        || option_strings[IX86_FUNCTION_SPECIFIC_TUNE]
>>> > -      || enum_opts_set.x_ix86_fpmath)
>>> > +      || enum_opts_set.x_ix86_fpmath
>>> > +      || !TARGET_64BIT_P (opts->x_ix86_isa_flags))
>>>
>>> You should use (!TARGET_64BIT_P ... && TARGET_SSE_P ...) to match the
>>> condition in the special fpmath processing part. (BTW: The comment in
>>> that part is wrong, we need SSE, not sse2 on 32-bit targets to use SSE
>>> math.)
>>
>> Hmpf, with the change I again run into the libgo bootstrap fail
>> (appearantly my reduced testcase is incomplete)
>>
>> libtool: compile:  /abuild/rguenther/obj2/./gcc/xgcc
>> -B/abuild/rguenther/obj2/./gcc/ -B/usr/local/x86_64-pc-linux-gnu/bin/
>> -B/usr/local/x86_64-pc-linux-gnu/lib/ -isystem
>> /usr/local/x86_64-pc-linux-gnu/include -isystem
>> /usr/local/x86_64-pc-linux-gnu/sys-include -m32 -DHAVE_CONFIG_H -I.
>> -I/space/rguenther/src/svn/trunk2/libgo -I
>> /space/rguenther/src/svn/trunk2/libgo/runtime
>> -I/space/rguenther/src/svn/trunk2/libgo/../libffi/include
>> -I../libffi/include -pthread -fexceptions -fnon-call-exceptions
>> -fplan9-extensions -fsplit-stack -Wall -Wextra -Wwrite-strings -Wcast-qual
>> -Werror -minline-all-stringops -D_GNU_SOURCE -D_LARGEFILE_SOURCE
>> -D_FILE_OFFSET_BITS=64 -I /space/rguenther/src/svn/trunk2/libgo/../libgcc
>> -I /space/rguenther/src/svn/trunk2/libgo/../libbacktrace -I
>> ../../../gcc/include -g -O2 -m32 -MT aeshash.lo -MD -MP -MF
>> .deps/aeshash.Tpo -c
>> /space/rguenther/src/svn/trunk2/libgo/runtime/aeshash.c  -fPIC -DPIC -o
>> .libs/aeshash.o
>> In file included from
>> /space/rguenther/src/svn/trunk2/libgo/runtime/aeshash.c:17:0:
>> /space/rguenther/src/svn/trunk2/libgo/runtime/aeshash.c: In function
>> ‘aeshashbody’:
>> /abuild/rguenther/obj2/./gcc/include/emmintrin.h:700:1: error: inlining
>> failed in call to always_inline ‘_mm_loadu_si128’: target specific option
>> mismatch
>>  _mm_loadu_si128 (__m128i_u const *__P)
>>  ^~~~~~~~~~~~~~~
>> /space/rguenther/src/svn/trunk2/libgo/runtime/aeshash.c:387:11: note:
>> called from here
>>   mseed ^= _mm_loadu_si128(aeskeysched.__values);
>>            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> that appens even with making the if a if (1).  The check we run into
>> is somehow still
>>
>>   else if (caller_opts->x_ix86_fpmath != callee_opts->x_ix86_fpmath)
>>     ret = false;
>>
>> ah ...
>>
>> #ifndef __SSE__
>> #pragma GCC push_options
>> #pragma GCC target("sse")
>> #define __DISABLE_SSE__
>> #endif /* __SSE__ */
>>
>> but on x86_64 when building with -m32 we _do_ have __SSE__ set so
>> the intrinsics get target_option_default_node which doesn't have
>> fmpath=sse.  So x86_64 -m32 -march=i586 enables SSE math for
>> the intrinsics while x86_64 -m32 [-march=x86-64] does not...
>
> IMO target_default_node should already enable fpmath=sse. When SSE is
> available, fpmath should be set to SSE, unless there is fpmath option
> specified.

Following part from ix86_option_override_internal looks a bit mismatched:

--cut here--
  /* For all chips supporting SSE2, -mfpmath=sse performs better than
     fpmath=387.  The second is however default at many targets since the
     extra 80bit precision of temporaries is considered to be part of ABI.
     Overwrite the default at least for -ffast-math.
     TODO: -mfpmath=both seems to produce same performing code with bit
     smaller binaries.  It is however not clear if register allocation is
     ready for this setting.
     Also -mfpmath=387 is overall a lot more compact (bout 4-5%) than SSE
     codegen.  We may switch to 387 with -ffast-math for size optimized
     functions. */
  else if (fast_math_flags_set_p (&global_options)
       && TARGET_SSE2_P (opts->x_ix86_isa_flags))
    opts->x_ix86_fpmath = FPMATH_SSE;
--cut here--

We probably have to set fpmath to SSE also for (!TARGET_64BIT_P ... &&
TARGET_SSE_P ...).

Uros.