falkTX
/
FFmpeg
mirror of https://github.com/falkTX/FFmpeg.git
1
0
Fork 0
Code Issues 0 Releases 338 Wiki Activity
Browse Source

h264: assembly version of get_cabac for x86_64 with PIC (v4) 

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.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
tags/n0.11
Roland Scheidegger Michael Niedermayer 13 years ago
parent
3194ab78a6
commit
a812b599b5
3 changed files with 125 additions and 25 deletions
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. +1
    -1
      libavcodec/h264_cabac.c
  2. +82
    -8
      libavcodec/x86/cabac.h
  3. +42
    -16
      libavcodec/x86/h264_i386.h

+ 1
- 1
libavcodec/h264_cabac.c View File

@@ -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 {


+ 82
- 8
libavcodec/x86/cabac.h View File

@@ -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 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 ff_h264_norm_shift-1b("rip", "rangeq"), %%ecx \n\t"\
"shl %%cl , "range" \n\t"\
"movzbl 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 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
int *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)


+ 42
- 16
libavcodec/x86/h264_i386.h View File

@@ -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
int *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
int *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"

"movzbl "MANGLE(last_coeff_flag_offset_8x8)"(%k6), %k6\n\t"
#ifdef BROKEN_RELOCATIONS
"movzbl last_coeff_flag_offset_8x8-1b(%14, %q6), %k6\n\t"
#else
"movzbl 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;


Write Preview
Loading…
Cancel
Save