ref: 8188096640e843767efa11b7d66d37eede807072
dir: /vp8/common/arm/neon/idct_dequant_full_2x_neon.asm/
;
; Copyright (c) 2010 The Webm project authors. All Rights Reserved.
;
; Use of this source code is governed by a BSD-style license
; that can be found in the LICENSE file in the root of the source
; tree. An additional intellectual property rights grant can be found
; in the file PATENTS. All contributing project authors may
; be found in the AUTHORS file in the root of the source tree.
;
EXPORT |idct_dequant_full_2x_neon|
ARM
REQUIRE8
PRESERVE8
AREA ||.text||, CODE, READONLY, ALIGN=2
;void idct_dequant_full_2x_neon(short *q, short *dq,
; unsigned char *dst, int stride);
; r0 *q,
; r1 *dq,
; r2 *dst
; r3 stride
|idct_dequant_full_2x_neon| PROC
vpush {d8-d15}
vld1.16 {q0, q1}, [r1] ; dq (same l/r)
vld1.16 {q2, q3}, [r0] ; l q
add r0, r0, #32
vld1.16 {q4, q5}, [r0] ; r q
add r12, r2, #4
; interleave the predictors
vld1.32 {d28[0]}, [r2], r3 ; l pre
vld1.32 {d28[1]}, [r12], r3 ; r pre
vld1.32 {d29[0]}, [r2], r3
vld1.32 {d29[1]}, [r12], r3
vld1.32 {d30[0]}, [r2], r3
vld1.32 {d30[1]}, [r12], r3
vld1.32 {d31[0]}, [r2], r3
vld1.32 {d31[1]}, [r12]
adr r1, cospi8sqrt2minus1 ; pointer to the first constant
; dequant: q[i] = q[i] * dq[i]
vmul.i16 q2, q2, q0
vmul.i16 q3, q3, q1
vmul.i16 q4, q4, q0
vmul.i16 q5, q5, q1
vld1.16 {d0}, [r1]
; q2: l0r0 q3: l8r8
; q4: l4r4 q5: l12r12
vswp d5, d8
vswp d7, d10
; _CONSTANTS_ * 4,12 >> 16
; q6: 4 * sinpi : c1/temp1
; q7: 12 * sinpi : d1/temp2
; q8: 4 * cospi
; q9: 12 * cospi
vqdmulh.s16 q6, q4, d0[2] ; sinpi8sqrt2
vqdmulh.s16 q7, q5, d0[2]
vqdmulh.s16 q8, q4, d0[0] ; cospi8sqrt2minus1
vqdmulh.s16 q9, q5, d0[0]
vqadd.s16 q10, q2, q3 ; a1 = 0 + 8
vqsub.s16 q11, q2, q3 ; b1 = 0 - 8
; vqdmulh only accepts signed values. this was a problem because
; our constant had the high bit set, and was treated as a negative value.
; vqdmulh also doubles the value before it shifts by 16. we need to
; compensate for this. in the case of sinpi8sqrt2, the lowest bit is 0,
; so we can shift the constant without losing precision. this avoids
; shift again afterward, but also avoids the sign issue. win win!
; for cospi8sqrt2minus1 the lowest bit is 1, so we lose precision if we
; pre-shift it
vshr.s16 q8, q8, #1
vshr.s16 q9, q9, #1
; q4: 4 + 4 * cospi : d1/temp1
; q5: 12 + 12 * cospi : c1/temp2
vqadd.s16 q4, q4, q8
vqadd.s16 q5, q5, q9
; c1 = temp1 - temp2
; d1 = temp1 + temp2
vqsub.s16 q2, q6, q5
vqadd.s16 q3, q4, q7
; [0]: a1+d1
; [1]: b1+c1
; [2]: b1-c1
; [3]: a1-d1
vqadd.s16 q4, q10, q3
vqadd.s16 q5, q11, q2
vqsub.s16 q6, q11, q2
vqsub.s16 q7, q10, q3
; rotate
vtrn.32 q4, q6
vtrn.32 q5, q7
vtrn.16 q4, q5
vtrn.16 q6, q7
; idct loop 2
; q4: l 0, 4, 8,12 r 0, 4, 8,12
; q5: l 1, 5, 9,13 r 1, 5, 9,13
; q6: l 2, 6,10,14 r 2, 6,10,14
; q7: l 3, 7,11,15 r 3, 7,11,15
; q8: 1 * sinpi : c1/temp1
; q9: 3 * sinpi : d1/temp2
; q10: 1 * cospi
; q11: 3 * cospi
vqdmulh.s16 q8, q5, d0[2] ; sinpi8sqrt2
vqdmulh.s16 q9, q7, d0[2]
vqdmulh.s16 q10, q5, d0[0] ; cospi8sqrt2minus1
vqdmulh.s16 q11, q7, d0[0]
vqadd.s16 q2, q4, q6 ; a1 = 0 + 2
vqsub.s16 q3, q4, q6 ; b1 = 0 - 2
; see note on shifting above
vshr.s16 q10, q10, #1
vshr.s16 q11, q11, #1
; q10: 1 + 1 * cospi : d1/temp1
; q11: 3 + 3 * cospi : c1/temp2
vqadd.s16 q10, q5, q10
vqadd.s16 q11, q7, q11
; q8: c1 = temp1 - temp2
; q9: d1 = temp1 + temp2
vqsub.s16 q8, q8, q11
vqadd.s16 q9, q10, q9
; a1+d1
; b1+c1
; b1-c1
; a1-d1
vqadd.s16 q4, q2, q9
vqadd.s16 q5, q3, q8
vqsub.s16 q6, q3, q8
vqsub.s16 q7, q2, q9
; +4 >> 3 (rounding)
vrshr.s16 q4, q4, #3 ; lo
vrshr.s16 q5, q5, #3
vrshr.s16 q6, q6, #3 ; hi
vrshr.s16 q7, q7, #3
vtrn.32 q4, q6
vtrn.32 q5, q7
vtrn.16 q4, q5
vtrn.16 q6, q7
; adding pre
; input is still packed. pre was read interleaved
vaddw.u8 q4, q4, d28
vaddw.u8 q5, q5, d29
vaddw.u8 q6, q6, d30
vaddw.u8 q7, q7, d31
vmov.i16 q14, #0
vmov q15, q14
vst1.16 {q14, q15}, [r0] ; write over high input
sub r0, r0, #32
vst1.16 {q14, q15}, [r0] ; write over low input
sub r2, r2, r3, lsl #2 ; dst - 4*stride
add r1, r2, #4 ; hi
;saturate and narrow
vqmovun.s16 d0, q4 ; lo
vqmovun.s16 d1, q5
vqmovun.s16 d2, q6 ; hi
vqmovun.s16 d3, q7
vst1.32 {d0[0]}, [r2], r3 ; lo
vst1.32 {d0[1]}, [r1], r3 ; hi
vst1.32 {d1[0]}, [r2], r3
vst1.32 {d1[1]}, [r1], r3
vst1.32 {d2[0]}, [r2], r3
vst1.32 {d2[1]}, [r1], r3
vst1.32 {d3[0]}, [r2]
vst1.32 {d3[1]}, [r1]
vpop {d8-d15}
bx lr
ENDP ; |idct_dequant_full_2x_neon|
; Constant Pool
cospi8sqrt2minus1 DCD 0x4e7b
; because the lowest bit in 0x8a8c is 0, we can pre-shift this
sinpi8sqrt2 DCD 0x4546
END