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optimize IDCT of rows with mostly zero coefficients 

Originally committed as revision 7790 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Måns Rullgård 2007-01-31 23:04:56 +00:00
parent 4302963daa
commit 118a49b0b7
1 changed files with 55 additions and 2 deletions
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57
libavcodec/armv4l/simple_idct_armv6.S
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@ -89,6 +89,32 @@ w57: .long W57
smlsd v4, a3, ip, v4 /* A3 += W4*row[4] - W6*row[6] */
.endm
/*
Compute partial IDCT of half row.
shift = left-shift amount
a3 = row[2,0]
a4 = row[3,1]
Output in registers v1--v8
*/
.macro idct_row4 shift
ldr ip, [pc, #(w42-.-8)] /* ip = W4 | (W2 << 16) */
ldr lr, [pc, #(w46-.-8)] /* lr = W4 | (W6 << 16) */
ldr v7, [pc, #(w57-.-8)] /* v7 = W5 | (W7 << 16) */
mov a2, #(1<<(\shift-1))
smlad v1, a3, ip, a2
smlsd v4, a3, ip, a2
ldr ip, [pc, #(w13-.-8)] /* ip = W1 | (W3 << 16) */
smlad v2, a3, lr, a2
smlsd v3, a3, lr, a2
smusdx fp, a4, v7 /* fp = B3 = W7*row[1] - W5*row[3] */
smuad v5, a4, ip /* v5 = B0 = W1*row[1] + W3*row[3] */
pkhtb a3, ip, v7, asr #16 /* a4 = W7 | (W3 << 16) */
pkhbt a2, ip, v7, lsl #16 /* a2 = W1 | (W5 << 16) */
smusdx v6, a3, a4 /* v6 = -B1 = W7*row[3] - W3*row[1] */
smusdx v7, a4, a2 /* v7 = B2 = W5*row[1] - W1*row[3] */
.endm
/*
Compute final part of IDCT single row without shift.
Input in registers v1--v8
@ -167,10 +193,26 @@ w57: .long W57
.align
.func idct_row_armv6
idct_row_armv6:
stmfd sp!, {a2, lr}
str lr, [sp, #-4]!
ldr lr, [a1, #12] /* lr = row[7,5] */
ldr ip, [a1, #4] /* ip = row[6,4] */
ldr a4, [a1, #8] /* a4 = row[3,1] */
ldr a3, [a1] /* a3 = row[2,0] */
orrs lr, lr, ip
cmpeq lr, a4
cmpeq lr, a3, lsr #16
beq 1f
str a2, [sp, #-4]!
cmp lr, #0
beq 2f
idct_row ROW_SHIFT
ldr a2, [sp], #4
b 3f
2: idct_row4 ROW_SHIFT
3: ldr a2, [sp], #4
idct_finish_shift ROW_SHIFT
strh v1, [a2]
@ -183,6 +225,17 @@ idct_row_armv6:
strh v5, [a2, #(16*7)]
ldr pc, [sp], #4
1: mov a3, a3, lsl #3
strh a3, [a2]
strh a3, [a2, #(16*2)]
strh a3, [a2, #(16*4)]
strh a3, [a2, #(16*6)]
strh a3, [a2, #(16*1)]
strh a3, [a2, #(16*3)]
strh a3, [a2, #(16*5)]
strh a3, [a2, #(16*7)]
ldr pc, [sp], #4
.endfunc
/*