[FFmpeg-cvslog] armv6: Accelerate ff_fft_calc for general case (nbits != 4)
Ben Avison
git at videolan.org
Fri Jul 18 03:12:14 CEST 2014
ffmpeg | branch: master | Ben Avison <bavison at riscosopen.org> | Wed Jul 16 16:02:01 2014 +0100| [87552d54d3337c3241e8a9e1a05df16eaa821496] | committer: Martin Storsjö
armv6: Accelerate ff_fft_calc for general case (nbits != 4)
The previous implementation targeted DTS Coherent Acoustics, which only
requires nbits == 4 (fft16()). This case was (and still is) linked directly
rather than being indirected through ff_fft_calc_vfp(), but now the full
range from radix-4 up to radix-65536 is available. This benefits other codecs
such as AAC and AC3.
The implementaion is based upon the C version, with each routine larger than
radix-16 calling a hierarchy of smaller FFT functions, then performing a
post-processing pass. This pass benefits a lot from loop unrolling to
counter the long pipelines in the VFP. A relaxed calling standard also
reduces the overhead of the call hierarchy, and avoiding the excessive
inlining performed by GCC probably helps with I-cache utilisation too.
I benchmarked the result by measuring the number of gperftools samples that
hit anywhere in the AAC decoder (starting from aac_decode_frame()) or
specifically in the FFT routines (fft4() to fft512() and pass()) for the
same sample AAC stream:
Before After
Mean StdDev Mean StdDev Confidence Change
Audio decode 2245.5 53.1 1599.6 43.8 100.0% +40.4%
FFT routines 940.6 22.0 348.1 20.8 100.0% +170.2%
Signed-off-by: Martin Storsjö <martin at martin.st>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=87552d54d3337c3241e8a9e1a05df16eaa821496
---
libavcodec/arm/fft_init_arm.c | 8 +-
libavcodec/arm/fft_vfp.S | 264 ++++++++++++++++++++++++++++++++++++++---
2 files changed, 255 insertions(+), 17 deletions(-)
diff --git a/libavcodec/arm/fft_init_arm.c b/libavcodec/arm/fft_init_arm.c
index 3a3d1a7..bc143c1 100644
--- a/libavcodec/arm/fft_init_arm.c
+++ b/libavcodec/arm/fft_init_arm.c
@@ -23,6 +23,8 @@
#include "libavcodec/rdft.h"
#include "libavcodec/synth_filter.h"
+void ff_fft_calc_vfp(FFTContext *s, FFTComplex *z);
+
void ff_fft_permute_neon(FFTContext *s, FFTComplex *z);
void ff_fft_calc_neon(FFTContext *s, FFTComplex *z);
@@ -38,10 +40,10 @@ av_cold void ff_fft_init_arm(FFTContext *s)
{
int cpu_flags = av_get_cpu_flags();
- if (have_vfp(cpu_flags)) {
+ if (have_vfp(cpu_flags) && !have_vfpv3(cpu_flags)) {
+ s->fft_calc = ff_fft_calc_vfp;
#if CONFIG_MDCT
- if (!have_vfpv3(cpu_flags))
- s->imdct_half = ff_imdct_half_vfp;
+ s->imdct_half = ff_imdct_half_vfp;
#endif
}
diff --git a/libavcodec/arm/fft_vfp.S b/libavcodec/arm/fft_vfp.S
index 7845ebb..130d529 100644
--- a/libavcodec/arm/fft_vfp.S
+++ b/libavcodec/arm/fft_vfp.S
@@ -21,8 +21,39 @@
#include "libavutil/arm/asm.S"
-@ TODO: * FFTs wider than 16
-@ * dispatch code
+@ The fftx_internal_vfp versions of the functions obey a modified AAPCS:
+@ VFP is in RunFast mode, vector length 4, stride 1 thoroughout, and
+@ all single-precision VFP registers may be corrupted on exit. The a2
+@ register may not be clobbered in these functions, as it holds the
+@ stored original FPSCR.
+
+function ff_fft_calc_vfp, export=1
+ ldr ip, [a1, #0] @ nbits
+ mov a1, a2
+A ldr pc, [pc, ip, lsl #2]
+A .word 0
+A .word 0
+A .word 0
+T movrel a2, (fft_tab_vfp - 8)
+T ldr pc, [a2, ip, lsl #2]
+T endfunc
+T const fft_tab_vfp
+ .word fft4_vfp
+ .word fft8_vfp
+ .word X(ff_fft16_vfp) @ this one alone is exported
+ .word fft32_vfp
+ .word fft64_vfp
+ .word fft128_vfp
+ .word fft256_vfp
+ .word fft512_vfp
+ .word fft1024_vfp
+ .word fft2048_vfp
+ .word fft4096_vfp
+ .word fft8192_vfp
+ .word fft16384_vfp
+ .word fft32768_vfp
+ .word fft65536_vfp
+A endfunc
function fft4_vfp
vldr d0, [a1, #0*2*4] @ s0,s1 = z[0]
@@ -131,18 +162,22 @@ endfunc
vstr d9, [a1, #3 * 2*4]
.endm
+function .Lfft8_internal_vfp
+ macro_fft8_head
+ macro_fft8_tail
+ bx lr
+endfunc
+
function fft8_vfp
ldr a3, =0x03030000 @ RunFast mode, vector length 4, stride 1
fmrx a2, FPSCR
fmxr FPSCR, a3
vpush {s16-s31}
-
- macro_fft8_head
- macro_fft8_tail
-
+ mov ip, lr
+ bl .Lfft8_internal_vfp
vpop {s16-s31}
fmxr FPSCR, a2
- bx lr
+ bx ip
endfunc
.align 3
@@ -153,12 +188,7 @@ cos1pi8: @ cos(1*pi/8) = sqrt(2+sqrt(2))/2
cos3pi8: @ cos(2*pi/8) = sqrt(2-sqrt(2))/2
.float 0.3826834261417388916015625
-function ff_fft16_vfp, export=1
- ldr a3, =0x03030000 @ RunFast mode, vector length 4, stride 1
- fmrx a2, FPSCR
- fmxr FPSCR, a3
- vpush {s16-s31}
-
+function .Lfft16_internal_vfp
macro_fft8_head
@ FFT4(z+8)
vldr d10, [a1, #8 * 2*4]
@@ -292,7 +322,213 @@ function ff_fft16_vfp, export=1
vstr d8, [a1, #0 * 2*4]
vstr d9, [a1, #4 * 2*4]
+ bx lr
+endfunc
+
+function ff_fft16_vfp, export=1
+ ldr a3, =0x03030000 @ RunFast mode, vector length 4, stride 1
+ fmrx a2, FPSCR
+ fmxr FPSCR, a3
+ vpush {s16-s31}
+ mov ip, lr
+ bl .Lfft16_internal_vfp
vpop {s16-s31}
fmxr FPSCR, a2
- bx lr
+ bx ip
+endfunc
+
+.macro pass n, z0, z1, z2, z3
+ add v6, v5, #4*2*\n
+ @ TRANSFORM_ZERO(z[0],z[o1],z[o2],z[o3])
+ @ TRANSFORM(z[1],z[o1+1],z[o2+1],z[o3+1],wre[1],wim[-1])
+ @ TRANSFORM(z[0],z[o1],z[o2],z[o3],wre[0],wim[0])
+ @ TRANSFORM(z[1],z[o1+1],z[o2+1],z[o3+1],wre[1],wim[-1])
+ vldr d8, [\z2, #8*(o2+1)] @ s16,s17
+ vldmdb v6!, {s2}
+ vldr d9, [\z3, #8*(o3+1)] @ s18,s19
+ vldmia v5!, {s0,s1} @ s0 is unused
+ vldr s7, [\z2, #8*o2] @ t1
+ vmul.f s20, s16, s2 @ vector * scalar
+ vldr s0, [\z3, #8*o3] @ t5
+ vldr s6, [\z2, #8*o2+4] @ t2
+ vldr s3, [\z3, #8*o3+4] @ t6
+ vmul.f s16, s16, s1 @ vector * scalar
+ ldr a4, =\n-1
+1: add \z0, \z0, #8*2
+ .if \n*4*2 >= 512
+ add \z1, \z1, #8*2
+ .endif
+ .if \n*4*2 >= 256
+ add \z2, \z2, #8*2
+ .endif
+ .if \n*4*2 >= 512
+ add \z3, \z3, #8*2
+ .endif
+ @ up to 2 stalls (VFP vector issuing / waiting for s0)
+ @ depending upon whether this is the first iteration and
+ @ how many add instructions are inserted above
+ vadd.f s4, s0, s7 @ t5
+ vadd.f s5, s6, s3 @ t6
+ vsub.f s6, s6, s3 @ t4
+ vsub.f s7, s0, s7 @ t3
+ vldr d6, [\z0, #8*0-8*2] @ s12,s13
+ vadd.f s0, s16, s21 @ t1
+ vldr d7, [\z1, #8*o1-8*2] @ s14,s15
+ vsub.f s1, s18, s23 @ t5
+ vadd.f s8, s4, s12 @ vector + vector
+ @ stall (VFP vector issuing)
+ @ stall (VFP vector issuing)
+ @ stall (VFP vector issuing)
+ vsub.f s4, s12, s4
+ vsub.f s5, s13, s5
+ vsub.f s6, s14, s6
+ vsub.f s7, s15, s7
+ vsub.f s2, s17, s20 @ t2
+ vadd.f s3, s19, s22 @ t6
+ vstr d4, [\z0, #8*0-8*2] @ s8,s9
+ vstr d5, [\z1, #8*o1-8*2] @ s10,s11
+ @ stall (waiting for s5)
+ vstr d2, [\z2, #8*o2-8*2] @ s4,s5
+ vadd.f s4, s1, s0 @ t5
+ vstr d3, [\z3, #8*o3-8*2] @ s6,s7
+ vsub.f s7, s1, s0 @ t3
+ vadd.f s5, s2, s3 @ t6
+ vsub.f s6, s2, s3 @ t4
+ vldr d6, [\z0, #8*1-8*2] @ s12,s13
+ vldr d7, [\z1, #8*(o1+1)-8*2] @ s14,s15
+ vldr d4, [\z2, #8*o2] @ s8,s9
+ vldmdb v6!, {s2,s3}
+ vldr d5, [\z3, #8*o3] @ s10,s11
+ vadd.f s20, s4, s12 @ vector + vector
+ vldmia v5!, {s0,s1}
+ vldr d8, [\z2, #8*(o2+1)] @ s16,s17
+ @ stall (VFP vector issuing)
+ vsub.f s4, s12, s4
+ vsub.f s5, s13, s5
+ vsub.f s6, s14, s6
+ vsub.f s7, s15, s7
+ vmul.f s12, s8, s3 @ vector * scalar
+ vstr d10, [\z0, #8*1-8*2] @ s20,s21
+ vldr d9, [\z3, #8*(o3+1)] @ s18,s19
+ vstr d11, [\z1, #8*(o1+1)-8*2] @ s22,s23
+ vmul.f s8, s8, s0 @ vector * scalar
+ vstr d2, [\z2, #8*(o2+1)-8*2] @ s4,s5
+ @ stall (waiting for s7)
+ vstr d3, [\z3, #8*(o3+1)-8*2] @ s6,s7
+ vmul.f s20, s16, s2 @ vector * scalar
+ @ stall (VFP vector issuing)
+ @ stall (VFP vector issuing)
+ @ stall (VFP vector issuing)
+ vadd.f s7, s8, s13 @ t1
+ vsub.f s6, s9, s12 @ t2
+ vsub.f s0, s10, s15 @ t5
+ vadd.f s3, s11, s14 @ t6
+ vmul.f s16, s16, s1 @ vector * scalar
+ subs a4, a4, #1
+ bne 1b
+ @ What remains is identical to the first two indentations of
+ @ the above, but without the increment of z
+ vadd.f s4, s0, s7 @ t5
+ vadd.f s5, s6, s3 @ t6
+ vsub.f s6, s6, s3 @ t4
+ vsub.f s7, s0, s7 @ t3
+ vldr d6, [\z0, #8*0] @ s12,s13
+ vadd.f s0, s16, s21 @ t1
+ vldr d7, [\z1, #8*o1] @ s14,s15
+ vsub.f s1, s18, s23 @ t5
+ vadd.f s8, s4, s12 @ vector + vector
+ vsub.f s4, s12, s4
+ vsub.f s5, s13, s5
+ vsub.f s6, s14, s6
+ vsub.f s7, s15, s7
+ vsub.f s2, s17, s20 @ t2
+ vadd.f s3, s19, s22 @ t6
+ vstr d4, [\z0, #8*0] @ s8,s9
+ vstr d5, [\z1, #8*o1] @ s10,s11
+ vstr d2, [\z2, #8*o2] @ s4,s5
+ vadd.f s4, s1, s0 @ t5
+ vstr d3, [\z3, #8*o3] @ s6,s7
+ vsub.f s7, s1, s0 @ t3
+ vadd.f s5, s2, s3 @ t6
+ vsub.f s6, s2, s3 @ t4
+ vldr d6, [\z0, #8*1] @ s12,s13
+ vldr d7, [\z1, #8*(o1+1)] @ s14,s15
+ vadd.f s20, s4, s12 @ vector + vector
+ vsub.f s4, s12, s4
+ vsub.f s5, s13, s5
+ vsub.f s6, s14, s6
+ vsub.f s7, s15, s7
+ vstr d10, [\z0, #8*1] @ s20,s21
+ vstr d11, [\z1, #8*(o1+1)] @ s22,s23
+ vstr d2, [\z2, #8*(o2+1)] @ s4,s5
+ vstr d3, [\z3, #8*(o3+1)] @ s6,s7
+.endm
+
+.macro def_fft n, n2, n4
+function .Lfft\n\()_internal_vfp
+ .if \n >= 512
+ push {v1-v6,lr}
+ .elseif \n >= 256
+ push {v1-v2,v5-v6,lr}
+ .else
+ push {v1,v5-v6,lr}
+ .endif
+ mov v1, a1
+ bl .Lfft\n2\()_internal_vfp
+ add a1, v1, #8*(\n/4)*2
+ bl .Lfft\n4\()_internal_vfp
+ movrelx v5, X(ff_cos_\n), a1
+ add a1, v1, #8*(\n/4)*3
+ bl .Lfft\n4\()_internal_vfp
+ .if \n >= 512
+ .set o1, 0*(\n/4/2)
+ .set o2, 0*(\n/4/2)
+ .set o3, 0*(\n/4/2)
+ add v2, v1, #8*2*(\n/4/2)
+ add v3, v1, #8*4*(\n/4/2)
+ add v4, v1, #8*6*(\n/4/2)
+ pass (\n/4/2), v1, v2, v3, v4
+ pop {v1-v6,pc}
+ .elseif \n >= 256
+ .set o1, 2*(\n/4/2)
+ .set o2, 0*(\n/4/2)
+ .set o3, 2*(\n/4/2)
+ add v2, v1, #8*4*(\n/4/2)
+ pass (\n/4/2), v1, v1, v2, v2
+ pop {v1-v2,v5-v6,pc}
+ .else
+ .set o1, 2*(\n/4/2)
+ .set o2, 4*(\n/4/2)
+ .set o3, 6*(\n/4/2)
+ pass (\n/4/2), v1, v1, v1, v1
+ pop {v1,v5-v6,pc}
+ .endif
endfunc
+
+function fft\n\()_vfp
+ ldr a3, =0x03030000 /* RunFast mode, vector length 4, stride 1 */
+ fmrx a2, FPSCR
+ fmxr FPSCR, a3
+ vpush {s16-s31}
+ mov ip, lr
+ bl .Lfft\n\()_internal_vfp
+ vpop {s16-s31}
+ fmxr FPSCR, a2
+ bx ip
+endfunc
+
+.ltorg
+.endm
+
+ def_fft 32, 16, 8
+ def_fft 64, 32, 16
+ def_fft 128, 64, 32
+ def_fft 256, 128, 64
+ def_fft 512, 256, 128
+ def_fft 1024, 512, 256
+ def_fft 2048, 1024, 512
+ def_fft 4096, 2048, 1024
+ def_fft 8192, 4096, 2048
+ def_fft 16384, 8192, 4096
+ def_fft 32768, 16384, 8192
+ def_fft 65536, 32768, 16384
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