[FFmpeg-devel] [PATCH] h264: assembly version of get_cabac for x86_64 with PIC (v6)
Roland Scheidegger
rscheidegger_lists at hispeed.ch
Thu Apr 26 02:47:10 CEST 2012
Could someone please post the assembly generated on darwin for this?
I really have no idea why it doesn't work there.
(Though unless something obvious goes wrong with the mangling, I
probably won't see why it doesn't work on darwin neither when seeing the
assembly, but someone more versed with symbol resolve magic might.)
Roland
Am 26.04.2012 02:31, schrieb Roland Scheidegger:
> This adds a hand-optimized assembly version for get_cabac much like the
> existing one, but it works if the table offsets are RIP-relative.
> Compared to the non-RIP-relative version this adds 2 lea instructions
> and it needs one extra register.
> There is a surprisingly large performance improvement over the c version (more
> so than the generated assembly seems to suggest) just in get_cabac, I measured
> roughly 40% faster for get_cabac on a K8. However, overall the difference is
> not that big, I measured roughly 5% on a test clip on a K8 and a Core2.
> Hopefully it still compiles on x86 32bit...
> v2: incorporated feedback from Loren Merritt to avoid rip-relative movs
> for every table, and got rid of unnecessary @GOTPCREL.
> v3: apply similar fixes to the the decode_significance functions, and use
> same macro arguments for non-pic case.
> v4: prettify inline asm arguments, add a non-fast-cmov version (as I expect
> the c code to be faster otherwise since both cmov and sbb suck hard on a
> Prescott, even can't construct the mask with a 64bit shift as that's just as
> terrible - it's quite difficult to find usable instructions on that chip...).
> This is tested to work but not on a P4, in theory it _should_ be fast there.
> v5: based on suggestion by Reimar Döffinger add LABEL_MANGLE macros. Should
> hopefully fix compilation on Darwin (untested).
> v6: fixed and changed back mangle for non-pic case, whitespace, use void ptr
> ---
> libavcodec/h264_cabac.c | 2 +-
> libavcodec/x86/cabac.h | 90 ++++++++++++++++++++++++++++++++++++++++----
> libavcodec/x86/h264_i386.h | 56 ++++++++++++++++++++-------
> 3 files changed, 124 insertions(+), 24 deletions(-)
>
> diff --git a/libavcodec/h264_cabac.c b/libavcodec/h264_cabac.c
> index 65f2cb4..6c59d17 100644
> --- a/libavcodec/h264_cabac.c
> +++ b/libavcodec/h264_cabac.c
> @@ -1659,7 +1659,7 @@ decode_cabac_residual_internal(H264Context *h, DCTELEM *block,
> index[coeff_count++] = last;\
> }
> const uint8_t *sig_off = significant_coeff_flag_offset_8x8[MB_FIELD];
> -#if ARCH_X86 && HAVE_7REGS && !defined(BROKEN_RELOCATIONS)
> +#if ARCH_X86 && HAVE_7REGS
> coeff_count= decode_significance_8x8_x86(CC, significant_coeff_ctx_base, index,
> last_coeff_ctx_base, sig_off);
> } else {
> diff --git a/libavcodec/x86/cabac.h b/libavcodec/x86/cabac.h
> index 0c4419b..1dc1915 100644
> --- a/libavcodec/x86/cabac.h
> +++ b/libavcodec/x86/cabac.h
> @@ -24,8 +24,71 @@
> #include "libavcodec/cabac.h"
> #include "libavutil/attributes.h"
> #include "libavutil/x86_cpu.h"
> +#include "libavutil/internal.h"
> #include "config.h"
>
> +#ifdef BROKEN_RELOCATIONS
> +#define RIP_ARG , "r"(rip)
> +
> +#if HAVE_FAST_CMOV
> +#define BRANCHLESS_GET_CABAC_UPDATE(ret, retq, low, range, tmp) \
> + "cmp "low" , "tmp" \n\t"\
> + "cmova %%ecx , "range" \n\t"\
> + "sbb %%rcx , %%rcx \n\t"\
> + "and %%ecx , "tmp" \n\t"\
> + "xor %%rcx , "retq" \n\t"\
> + "sub "tmp" , "low" \n\t"
> +#else /* HAVE_FAST_CMOV */
> +#define BRANCHLESS_GET_CABAC_UPDATE(ret, retq, low, range, tmp) \
> +/* P4 Prescott has crappy cmov,sbb,64bit shift so avoid them */ \
> + "sub "low" , "tmp" \n\t"\
> + "sar $31 , "tmp" \n\t"\
> + "sub %%ecx , "range" \n\t"\
> + "and "tmp" , "range" \n\t"\
> + "add %%ecx , "range" \n\t"\
> + "shl $17 , %%ecx \n\t"\
> + "and "tmp" , %%ecx \n\t"\
> + "sub %%ecx , "low" \n\t"\
> + "xor "tmp" , "ret" \n\t"\
> + "movslq "ret" , "retq" \n\t"
> +#endif /* HAVE_FAST_CMOV */
> +
> +#define BRANCHLESS_GET_CABAC(ret, retq, statep, low, lowword, range, rangeq, tmp, tmpbyte, byte, end, rip) \
> + "movzbl "statep" , "ret" \n\t"\
> + "mov "range" , "tmp" \n\t"\
> + "and $0xC0 , "range" \n\t"\
> + "lea ("ret", "range", 2), %%ecx \n\t"\
> + "movzbl "LABEL_MANGLE(ff_h264_lps_range)"-1b("rip", %%rcx), "range" \n\t"\
> + "sub "range" , "tmp" \n\t"\
> + "mov "tmp" , %%ecx \n\t"\
> + "shl $17 , "tmp" \n\t"\
> + BRANCHLESS_GET_CABAC_UPDATE(ret, retq, low, range, tmp) \
> + "movzbl "LABEL_MANGLE(ff_h264_norm_shift)"-1b("rip", "rangeq"), %%ecx \n\t"\
> + "shl %%cl , "range" \n\t"\
> + "movzbl "LABEL_MANGLE(ff_h264_mlps_state)"-1b+128("rip", "retq"), "tmp" \n\t"\
> + "shl %%cl , "low" \n\t"\
> + "mov "tmpbyte" , "statep" \n\t"\
> + "test "lowword" , "lowword" \n\t"\
> + "jnz 2f \n\t"\
> + "mov "byte" , %%"REG_c" \n\t"\
> + "add"OPSIZE" $2 , "byte" \n\t"\
> + "movzwl (%%"REG_c") , "tmp" \n\t"\
> + "lea -1("low") , %%ecx \n\t"\
> + "xor "low" , %%ecx \n\t"\
> + "shr $15 , %%ecx \n\t"\
> + "bswap "tmp" \n\t"\
> + "shr $15 , "tmp" \n\t"\
> + "movzbl "LABEL_MANGLE(ff_h264_norm_shift)"-1b("rip", %%rcx), %%ecx \n\t"\
> + "sub $0xFFFF , "tmp" \n\t"\
> + "neg %%ecx \n\t"\
> + "add $7 , %%ecx \n\t"\
> + "shl %%cl , "tmp" \n\t"\
> + "add "tmp" , "low" \n\t"\
> + "2: \n\t"
> +
> +#else /* BROKEN_RELOCATIONS */
> +#define RIP_ARG
> +
> #if HAVE_FAST_CMOV
> #define BRANCHLESS_GET_CABAC_UPDATE(ret, statep, low, range, tmp)\
> "mov "tmp" , %%ecx \n\t"\
> @@ -51,7 +114,7 @@
> "xor "tmp" , "ret" \n\t"
> #endif /* HAVE_FAST_CMOV */
>
> -#define BRANCHLESS_GET_CABAC(ret, statep, low, lowword, range, tmp, tmpbyte, byte, end) \
> +#define BRANCHLESS_GET_CABAC(ret, retq, statep, low, lowword, range, rangeq, tmp, tmpbyte, byte, end, rip) \
> "movzbl "statep" , "ret" \n\t"\
> "mov "range" , "tmp" \n\t"\
> "and $0xC0 , "range" \n\t"\
> @@ -81,28 +144,39 @@
> "add "tmp" , "low" \n\t"\
> "2: \n\t"
>
> +#endif /* BROKEN_RELOCATIONS */
>
> -#if HAVE_7REGS && !defined(BROKEN_RELOCATIONS) && !(defined(__i386) && defined(__clang__) && (__clang_major__<2 || (__clang_major__==2 && __clang_minor__<10)))\
> - && !(defined(__i386) && !defined(__clang__) && defined(__llvm__) && __GNUC__==4 && __GNUC_MINOR__==2 && __GNUC_PATCHLEVEL__<=1)
> +
> +#if HAVE_7REGS && !(defined(__i386) && defined(__clang__) && (__clang_major__<2 || (__clang_major__==2 && __clang_minor__<10)))\
> + && !(defined(__i386) && !defined(__clang__) && defined(__llvm__) && __GNUC__==4 && __GNUC_MINOR__==2 && __GNUC_PATCHLEVEL__<=1)
> #define get_cabac_inline get_cabac_inline_x86
> static av_always_inline int get_cabac_inline_x86(CABACContext *c,
> uint8_t *const state)
> {
> int bit, tmp;
> +#ifdef BROKEN_RELOCATIONS
> + void *rip;
> +
> + __asm__ volatile(
> + "1: \n\t"
> + "lea 1b(%%rip), %0 \n\t"
> + : "=&r"(rip)
> + );
> +#endif
>
> __asm__ volatile(
> - BRANCHLESS_GET_CABAC("%0", "(%4)", "%1", "%w1",
> - "%2", "%3", "%b3",
> - "%a6(%5)", "%a7(%5)")
> + BRANCHLESS_GET_CABAC("%0", "%q0", "(%4)", "%1", "%w1",
> + "%2", "%q2", "%3", "%b3",
> + "%a6(%5)", "%a7(%5)", "%8")
> : "=&r"(bit), "+&r"(c->low), "+&r"(c->range), "=&q"(tmp)
> : "r"(state), "r"(c),
> "i"(offsetof(CABACContext, bytestream)),
> - "i"(offsetof(CABACContext, bytestream_end))
> + "i"(offsetof(CABACContext, bytestream_end)) RIP_ARG
> : "%"REG_c, "memory"
> );
> return bit & 1;
> }
> -#endif /* HAVE_7REGS && !defined(BROKEN_RELOCATIONS) */
> +#endif /* HAVE_7REGS */
>
> #define get_cabac_bypass_sign get_cabac_bypass_sign_x86
> static av_always_inline int get_cabac_bypass_sign_x86(CABACContext *c, int val)
> diff --git a/libavcodec/x86/h264_i386.h b/libavcodec/x86/h264_i386.h
> index 6aa2d07..eed94e9 100644
> --- a/libavcodec/x86/h264_i386.h
> +++ b/libavcodec/x86/h264_i386.h
> @@ -36,7 +36,7 @@
>
> //FIXME use some macros to avoid duplicating get_cabac (cannot be done yet
> //as that would make optimization work hard)
> -#if HAVE_7REGS && !defined(BROKEN_RELOCATIONS)
> +#if HAVE_7REGS
> static int decode_significance_x86(CABACContext *c, int max_coeff,
> uint8_t *significant_coeff_ctx_base,
> int *index, x86_reg last_off){
> @@ -45,20 +45,31 @@ static int decode_significance_x86(CABACContext *c, int max_coeff,
> int minusindex= 4-(intptr_t)index;
> int bit;
> x86_reg coeff_count;
> +
> +#ifdef BROKEN_RELOCATIONS
> + void *rip;
> +
> + __asm__ volatile(
> + "1: \n\t"
> + "lea 1b(%%rip), %0 \n\t"
> + : "=&r"(rip)
> + );
> +#endif
> +
> __asm__ volatile(
> "3: \n\t"
>
> - BRANCHLESS_GET_CABAC("%4", "(%1)", "%3", "%w3",
> - "%5", "%k0", "%b0",
> - "%a11(%6)", "%a12(%6)")
> + BRANCHLESS_GET_CABAC("%4", "%q4", "(%1)", "%3", "%w3",
> + "%5", "%q5", "%k0", "%b0",
> + "%a11(%6)", "%a12(%6)", "%13")
>
> "test $1, %4 \n\t"
> " jz 4f \n\t"
> "add %10, %1 \n\t"
>
> - BRANCHLESS_GET_CABAC("%4", "(%1)", "%3", "%w3",
> - "%5", "%k0", "%b0",
> - "%a11(%6)", "%a12(%6)")
> + BRANCHLESS_GET_CABAC("%4", "%q4", "(%1)", "%3", "%w3",
> + "%5", "%q5", "%k0", "%b0",
> + "%a11(%6)", "%a12(%6)", "%13")
>
> "sub %10, %1 \n\t"
> "mov %2, %0 \n\t"
> @@ -86,7 +97,7 @@ static int decode_significance_x86(CABACContext *c, int max_coeff,
> "+&r"(c->low), "=&r"(bit), "+&r"(c->range)
> : "r"(c), "m"(minusstart), "m"(end), "m"(minusindex), "m"(last_off),
> "i"(offsetof(CABACContext, bytestream)),
> - "i"(offsetof(CABACContext, bytestream_end))
> + "i"(offsetof(CABACContext, bytestream_end)) RIP_ARG
> : "%"REG_c, "memory"
> );
> return coeff_count;
> @@ -100,6 +111,17 @@ static int decode_significance_8x8_x86(CABACContext *c,
> x86_reg coeff_count;
> x86_reg last=0;
> x86_reg state;
> +
> +#ifdef BROKEN_RELOCATIONS
> + void *rip;
> +
> + __asm__ volatile(
> + "1: \n\t"
> + "lea 1b(%%rip), %0 \n\t"
> + : "=&r"(rip)
> + );
> +#endif
> +
> __asm__ volatile(
> "mov %1, %6 \n\t"
> "3: \n\t"
> @@ -108,20 +130,24 @@ static int decode_significance_8x8_x86(CABACContext *c,
> "movzbl (%0, %6), %k6 \n\t"
> "add %9, %6 \n\t"
>
> - BRANCHLESS_GET_CABAC("%4", "(%6)", "%3", "%w3",
> - "%5", "%k0", "%b0",
> - "%a12(%7)", "%a13(%7)")
> + BRANCHLESS_GET_CABAC("%4", "%q4", "(%6)", "%3", "%w3",
> + "%5", "%q5", "%k0", "%b0",
> + "%a12(%7)", "%a13(%7)", "%14")
>
> "mov %1, %k6 \n\t"
> "test $1, %4 \n\t"
> " jz 4f \n\t"
>
> +#ifdef BROKEN_RELOCATIONS
> + "movzbl "LABEL_MANGLE(last_coeff_flag_offset_8x8)"-1b(%14, %q6), %k6\n\t"
> +#else
> "movzbl "MANGLE(last_coeff_flag_offset_8x8)"(%k6), %k6\n\t"
> +#endif
> "add %11, %6 \n\t"
>
> - BRANCHLESS_GET_CABAC("%4", "(%6)", "%3", "%w3",
> - "%5", "%k0", "%b0",
> - "%a12(%7)", "%a13(%7)")
> + BRANCHLESS_GET_CABAC("%4", "%q4", "(%6)", "%3", "%w3",
> + "%5", "%q5", "%k0", "%b0",
> + "%a12(%7)", "%a13(%7)", "%14")
>
> "mov %2, %0 \n\t"
> "mov %1, %k6 \n\t"
> @@ -147,7 +173,7 @@ static int decode_significance_8x8_x86(CABACContext *c,
> : "r"(c), "m"(minusindex), "m"(significant_coeff_ctx_base),
> "m"(sig_off), "m"(last_coeff_ctx_base),
> "i"(offsetof(CABACContext, bytestream)),
> - "i"(offsetof(CABACContext, bytestream_end))
> + "i"(offsetof(CABACContext, bytestream_end)) RIP_ARG
> : "%"REG_c, "memory"
> );
> return coeff_count;
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