[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 02:31:33 CEST 2012
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;
--
1.7.1
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