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FFmpeg/libavutil/cpu_internal.h
Andreas Rheinhardt ac322ec214 avutil/cpu_internal: Fix check for SSE2SLOW
For SSE2 and SSE3, there are four states that the two flags
involved (AV_CPU_FLAG_SSE[23] and AV_CPU_FLAG_SSE[23]SLOW) can convey.
When ordered from worst to best they are:
1. both flags unset (SSE[23] unavailable)
2. the slow flag set, the ordinary flag unset (this is designed
for cases where SSE2 is available, but so slow that MMX(EXT)/SSE
code is usually faster)
3. both flags set (SSE2 is available, but there might be scenarios
where MMX(EXT)/SSE code is faster)
4. the ordinary flag set, the slow flag unset (this is the normal case)

The ordinary macros for checking cpuflags return true
in the latter two cases; the fast macros only return true for
the latter case. Yet the macros to check for slow currently
only return true in case three.

This seems unintended. In fact, the only uses of the slow macros
are all of the form
if (EXTERNAL_SSE2(cpu_flags) || EXTERNAL_SSE2_SLOW(cpu_flags))
where the check for EXTERNAL_SSE2_SLOW is completely redundant.
Even more importantly, it is not what was intended. Before
6369ba3c9c, the checks passed
in cases 2 to 4. Said commit changed this to something that
only passes for the third case. Commits
7fb758cd8e and
c1913064e3 restored the old behaviour,
yet merging 4efab89332 (in commit
ac774cfa57) broke this again
by changing it to what it is now.*

This commit changes the macros to make the slow macros check
whether a specific instruction is supported, even if slow.
This restores the intended meaning to all uses of the SLOW macros
and is generally more natural.

*: Libav only checks for EXTERNAL_SSE2_SLOW, i.e. for the third case
only.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-06-18 19:25:03 +02:00

62 lines
2.4 KiB
C

/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVUTIL_CPU_INTERNAL_H
#define AVUTIL_CPU_INTERNAL_H
#include "config.h"
#include "cpu.h"
#define CPUEXT_SUFFIX(flags, suffix, cpuext) \
(HAVE_ ## cpuext ## suffix && ((flags) & AV_CPU_FLAG_ ## cpuext))
#define CPUEXT_SUFFIX_FAST2(flags, suffix, cpuext, slow_cpuext) \
(HAVE_ ## cpuext ## suffix && ((flags) & AV_CPU_FLAG_ ## cpuext) && \
!((flags) & AV_CPU_FLAG_ ## slow_cpuext ## SLOW))
#define CPUEXT_SUFFIX_SLOW(flags, suffix, cpuext) \
(HAVE_ ## cpuext ## suffix && \
((flags) & (AV_CPU_FLAG_ ## cpuext | AV_CPU_FLAG_ ## cpuext ## SLOW)))
#define CPUEXT_SUFFIX_SLOW2(flags, suffix, cpuext, slow_cpuext) \
(HAVE_ ## cpuext ## suffix && ((flags) & AV_CPU_FLAG_ ## cpuext) && \
((flags) & (AV_CPU_FLAG_ ## slow_cpuext | AV_CPU_FLAG_ ## slow_cpuext ## SLOW)))
#define CPUEXT_SUFFIX_FAST(flags, suffix, cpuext) CPUEXT_SUFFIX_FAST2(flags, suffix, cpuext, cpuext)
#define CPUEXT(flags, cpuext) CPUEXT_SUFFIX(flags, , cpuext)
#define CPUEXT_FAST(flags, cpuext) CPUEXT_SUFFIX_FAST(flags, , cpuext)
#define CPUEXT_SLOW(flags, cpuext) CPUEXT_SUFFIX_SLOW(flags, , cpuext)
int ff_get_cpu_flags_mips(void);
int ff_get_cpu_flags_aarch64(void);
int ff_get_cpu_flags_arm(void);
int ff_get_cpu_flags_ppc(void);
int ff_get_cpu_flags_x86(void);
int ff_get_cpu_flags_loongarch(void);
size_t ff_get_cpu_max_align_mips(void);
size_t ff_get_cpu_max_align_aarch64(void);
size_t ff_get_cpu_max_align_arm(void);
size_t ff_get_cpu_max_align_ppc(void);
size_t ff_get_cpu_max_align_x86(void);
size_t ff_get_cpu_max_align_loongarch(void);
#endif /* AVUTIL_CPU_INTERNAL_H */