I think you were looking at an older version of the patch. Newer version didn't have this. Anyhow, there's a new version I uploaded (v3).
On Thu, Feb 27, 2025 at 6:31 PM Lynne <d...@lynne.ee> wrote: > On 25/02/2025 22:37, Pranav Kant via ffmpeg-devel wrote: > > By default, all globals in C/C++ compiled by clang are allocated > > in non-large data sections. See [1] for background on code models. > > For PIC (Position independent code), this is fine as long as binary is > > small but as binary size increases, users maybe want to use medium/large > > code models (-mcmodel=medium) which moves data in to large sections. > > As data in these large sections cannot be accessed using PIC code > > anymore (as it may be too far away), compiler ends up using a different > > instruction sequence when building C/C++ code -- using GOT to access > > these globals (which can be relaxed by linker at link time if binary > > ends up being smaller). However, assembly files continue to access these > > globals defined in C/C++ files using older (and invalid instruction > > sequence). So, we mark all such globals with an attribute that forces > > them to be allocated in small sections allowing them to validly be > > accessed from the assembly code. > > > > This patch should not have any affect on builds that use small code > > model, which is the default mode. > > > > [1] > https://eli.thegreenplace.net/2012/01/03/understanding-the-x64-code-models > > --- > > libavcodec/ac3dsp.c | 2 +- > > libavcodec/cabac.c | 3 ++- > > libavcodec/x86/constants.c | 8 ++++++++ > > libavutil/attributes.h | 6 ++++++ > > 4 files changed, 17 insertions(+), 2 deletions(-) > > > > diff --git a/libavcodec/ac3dsp.c b/libavcodec/ac3dsp.c > > index 730fa70fff..43b4fcbda9 100644 > > --- a/libavcodec/ac3dsp.c > > +++ b/libavcodec/ac3dsp.c > > @@ -104,7 +104,7 @@ static void ac3_update_bap_counts_c(uint16_t > mant_cnt[16], uint8_t *bap, > > mant_cnt[bap[len]]++; > > } > > > > -DECLARE_ALIGNED(16, const uint16_t, ff_ac3_bap_bits)[16] = { > > +av_mcmodel_small DECLARE_ALIGNED(16, const uint16_t, > ff_ac3_bap_bits)[16] = { > > 0, 0, 0, 3, 0, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16 > > }; > > > > diff --git a/libavcodec/cabac.c b/libavcodec/cabac.c > > index 7d41cd2ae6..dfc3ba135a 100644 > > --- a/libavcodec/cabac.c > > +++ b/libavcodec/cabac.c > > @@ -24,12 +24,13 @@ > > * Context Adaptive Binary Arithmetic Coder. > > */ > > > > +#include "libavutil/attributes.h" > > #include "libavutil/error.h" > > #include "libavutil/mem_internal.h" > > > > #include "cabac.h" > > > > -DECLARE_ASM_ALIGNED(1, const uint8_t, ff_h264_cabac_tables)[512 + > 4*2*64 + 4*64 + 63] = { > > +av_mcmodel_small DECLARE_ASM_ALIGNED(1, const uint8_t, > ff_h264_cabac_tables)[512 + 4*2*64 + 4*64 + 63] = { > > 9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5, > > 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, > > 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3, > > diff --git a/libavcodec/x86/constants.c b/libavcodec/x86/constants.c > > index bc7f2b17b8..9a5af2871c 100644 > > --- a/libavcodec/x86/constants.c > > +++ b/libavcodec/x86/constants.c > > @@ -18,17 +18,21 @@ > > * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA > 02110-1301 USA > > */ > > > > +#include "libavutil/attributes.h" > > #include "libavutil/mem_internal.h" > > #include "libavutil/x86/asm.h" // for xmm_reg > > #include "constants.h" > > > > +av_mcmodel_small > > DECLARE_ALIGNED(32, const ymm_reg, ff_pw_1) = { > 0x0001000100010001ULL, 0x0001000100010001ULL, > > > 0x0001000100010001ULL, 0x0001000100010001ULL }; > > DECLARE_ALIGNED(32, const ymm_reg, ff_pw_2) = { > 0x0002000200020002ULL, 0x0002000200020002ULL, > > > 0x0002000200020002ULL, 0x0002000200020002ULL }; > > DECLARE_ASM_ALIGNED(16, const xmm_reg, ff_pw_3) = { > 0x0003000300030003ULL, 0x0003000300030003ULL }; > > +av_mcmodel_small > > DECLARE_ASM_ALIGNED(32, const ymm_reg, ff_pw_4) = { > 0x0004000400040004ULL, 0x0004000400040004ULL, > > > 0x0004000400040004ULL, 0x0004000400040004ULL }; > > +av_mcmodel_small > > DECLARE_ASM_ALIGNED(16, const xmm_reg, ff_pw_5) = { > 0x0005000500050005ULL, 0x0005000500050005ULL }; > > DECLARE_ALIGNED(16, const xmm_reg, ff_pw_8) = { > 0x0008000800080008ULL, 0x0008000800080008ULL }; > > DECLARE_ASM_ALIGNED(16, const xmm_reg, ff_pw_9) = { > 0x0009000900090009ULL, 0x0009000900090009ULL }; > > @@ -49,6 +53,7 @@ DECLARE_ALIGNED(32, const ymm_reg, ff_pw_256) = { > 0x0100010001000100ULL, 0x010 > > DECLARE_ALIGNED(32, const ymm_reg, ff_pw_512) = { > 0x0200020002000200ULL, 0x0200020002000200ULL, > > > 0x0200020002000200ULL, 0x0200020002000200ULL }; > > DECLARE_ALIGNED(16, const xmm_reg, ff_pw_1019) = { > 0x03FB03FB03FB03FBULL, 0x03FB03FB03FB03FBULL }; > > +av_mcmodel_small > > DECLARE_ALIGNED(32, const ymm_reg, ff_pw_1023) = { > 0x03ff03ff03ff03ffULL, 0x03ff03ff03ff03ffULL, > > > 0x03ff03ff03ff03ffULL, 0x03ff03ff03ff03ffULL}; > > DECLARE_ALIGNED(32, const ymm_reg, ff_pw_1024) = { > 0x0400040004000400ULL, 0x0400040004000400ULL, > > @@ -66,13 +71,16 @@ DECLARE_ALIGNED(32, const ymm_reg, ff_pw_m1) = { > 0xFFFFFFFFFFFFFFFFULL, 0xFFF > > > > DECLARE_ALIGNED(32, const ymm_reg, ff_pb_0) = { > 0x0000000000000000ULL, 0x0000000000000000ULL, > > > 0x0000000000000000ULL, 0x0000000000000000ULL }; > > +av_mcmodel_small > > DECLARE_ALIGNED(32, const ymm_reg, ff_pb_1) = { > 0x0101010101010101ULL, 0x0101010101010101ULL, > > > 0x0101010101010101ULL, 0x0101010101010101ULL }; > > DECLARE_ALIGNED(32, const ymm_reg, ff_pb_2) = { > 0x0202020202020202ULL, 0x0202020202020202ULL, > > > 0x0202020202020202ULL, 0x0202020202020202ULL }; > > +av_mcmodel_small > > DECLARE_ALIGNED(32, const ymm_reg, ff_pb_3) = { > 0x0303030303030303ULL, 0x0303030303030303ULL, > > > 0x0303030303030303ULL, 0x0303030303030303ULL }; > > DECLARE_ALIGNED(32, const xmm_reg, ff_pb_15) = { > 0x0F0F0F0F0F0F0F0FULL, 0x0F0F0F0F0F0F0F0FULL }; > > +av_mcmodel_small > > DECLARE_ALIGNED(32, const ymm_reg, ff_pb_80) = { > 0x8080808080808080ULL, 0x8080808080808080ULL, > > > 0x8080808080808080ULL, 0x8080808080808080ULL }; > > DECLARE_ALIGNED(32, const ymm_reg, ff_pb_FE) = { > 0xFEFEFEFEFEFEFEFEULL, 0xFEFEFEFEFEFEFEFEULL, > > diff --git a/libavutil/attributes.h b/libavutil/attributes.h > > index 04c615c952..704a7070db 100644 > > --- a/libavutil/attributes.h > > +++ b/libavutil/attributes.h > > @@ -104,6 +104,12 @@ > > # define attribute_deprecated > > #endif > > > > +#if defined(__clang__) && __has_attribute(model) > > +# define av_mcmodel_small __attribute__((model("small"))) > > +#else > > +# define av_mcmodel_small > > +#endif > > That's a bad macro name, moreover being a compiler-specific name. > Could you consider calling it simply av_global? > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
