--- /dev/null
+;
+; Copyright (c) 2013 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 |vp9_short_idct4x4_add_neon|
+ ARM
+ REQUIRE8
+ PRESERVE8
+
+ AREA ||.text||, CODE, READONLY, ALIGN=2
+
+ AREA Block, CODE, READONLY ; name this block of code
+;void vp9_short_idct4x4_add_neon(int16_t *input, uint8_t *dest, int dest_stride)
+;
+; r0 int16_t input
+; r1 uint8_t *dest
+; r2 int dest_stride)
+
+|vp9_short_idct4x4_add_neon| PROC
+
+ ; The 2D transform is done with two passes which are actually pretty
+ ; similar. We first transform the rows. This is done by transposing
+ ; the inputs, doing an SIMD column transform (the columns are the
+ ; transposed rows) and then transpose the results (so that it goes back
+ ; in normal/row positions). Then, we transform the columns by doing
+ ; another SIMD column transform.
+ ; So, two passes of a transpose followed by a column transform.
+
+ ; load the inputs into q8-q9, d16-d19
+ vld1.s16 {q8}, [r0]!
+ vld1.s16 {q9}, [r0]!
+
+ ; generate scalar constants
+ ; cospi_8_64 = 15137 = 0x3b21
+ mov r0, #0x3b00
+ add r0, #0x21
+ ; cospi_16_64 = 11585 = 0x2d41
+ mov r3, #0x2d00
+ add r3, #0x41
+ ; cospi_24_64 = 6270 = 0x 187e
+ mov r12, #0x1800
+ add r12, #0x7e
+ ; generate constant vectors
+ vdup.16 d20, r0; ; replicate cospi_8_64
+ vdup.16 d21, r3; ; replicate cospi_16_64
+ vdup.16 d22, r12; ; replicate cospi_24_64
+
+ ; transpose the input data
+ ; 00 01 02 03 d16
+ ; 10 11 12 13 d17
+ ; 20 21 22 23 d18
+ ; 30 31 32 33 d19
+ vtrn.16 d16, d17
+ vtrn.16 d18, d19
+ ; 00 10 02 12 d16
+ ; 01 11 03 13 d17
+ ; 20 30 22 32 d18
+ ; 21 31 23 33 d19
+ vtrn.32 q8, q9
+ ; 00 10 20 30 d16
+ ; 01 11 21 31 d17
+ ; 02 12 22 32 d18
+ ; 03 13 23 33 d19
+
+ ; do the transform on transposed rows
+
+ ; stage 1
+ ; (input[0] + input[2]) * cospi_16_64;
+ ; (input[0] - input[2]) * cospi_16_64;
+ vadd.s16 d23, d16, d18
+ vsub.s16 d24, d16, d18
+ vmull.s16 q13, d23, d21
+ vmull.s16 q14, d24, d21
+
+ ; input[1] * cospi_24_64 - input[3] * cospi_8_64;
+ ; input[1] * cospi_8_64 + input[3] * cospi_24_64;
+ vmull.s16 q15, d17, d22
+ vmull.s16 q0, d19, d20
+ vmull.s16 q1, d17, d20
+ vmull.s16 q2, d19, d22
+ vsub.s32 q3, q15, q0
+ vadd.s32 q8, q1, q2
+
+ ; dct_const_round_shift
+ vqrshrn.s32 d26, q13, #14
+ vqrshrn.s32 d27, q14, #14
+ vqrshrn.s32 d29, q3, #14
+ vqrshrn.s32 d28, q8, #14
+
+ ; stage 2
+ ; output[0] = step[0] + step[3];
+ ; output[1] = step[1] + step[2];
+ ; output[3] = step[0] - step[3];
+ ; output[2] = step[1] - step[2];
+ vadd.s16 q8, q13, q14
+ vsub.s16 q9, q13, q14
+ vswp d18, d19
+
+ ; transpose the results
+ ; 00 01 02 03 d16
+ ; 10 11 12 13 d17
+ ; 20 21 22 23 d18
+ ; 30 31 32 33 d19
+ vtrn.16 d16, d17
+ vtrn.16 d18, d19
+ ; 00 10 02 12 d16
+ ; 01 11 03 13 d17
+ ; 20 30 22 32 d18
+ ; 21 31 23 33 d19
+ vtrn.32 q8, q9
+ ; 00 10 20 30 d16
+ ; 01 11 21 31 d17
+ ; 02 12 22 32 d18
+ ; 03 13 23 33 d19
+
+ ; do the transform on columns
+
+ ; stage 1
+ ; (input[0] + input[2]) * cospi_16_64;
+ ; (input[0] - input[2]) * cospi_16_64;
+ vadd.s16 d23, d16, d18
+ vsub.s16 d24, d16, d18
+ vmull.s16 q13, d23, d21
+ vmull.s16 q14, d24, d21
+
+ ; input[1] * cospi_24_64 - input[3] * cospi_8_64;
+ ; input[1] * cospi_8_64 + input[3] * cospi_24_64;
+ vmull.s16 q15, d17, d22
+ vmull.s16 q0, d19, d20
+ vmull.s16 q1, d17, d20
+ vmull.s16 q2, d19, d22
+ vsub.s32 q3, q15, q0
+ vadd.s32 q8, q1, q2
+
+ ; dct_const_round_shift
+ vqrshrn.s32 d26, q13, #14
+ vqrshrn.s32 d27, q14, #14
+ vqrshrn.s32 d29, q3, #14
+ vqrshrn.s32 d28, q8, #14
+
+ ; stage 2
+ ; output[0] = step[0] + step[3];
+ ; output[1] = step[1] + step[2];
+ ; output[3] = step[0] - step[3];
+ ; output[2] = step[1] - step[2];
+ vadd.s16 q8, q13, q14
+ vsub.s16 q9, q13, q14
+
+ ; The results are in two registers, one of them being swapped. This will
+ ; be taken care of by loading the 'dest' value in a swapped fashion and
+ ; also storing them in the same swapped fashion.
+ ; temp_out[0, 1] = d16, d17 = q8
+ ; temp_out[2, 3] = d19, d18 = q9 swapped
+
+ ; ROUND_POWER_OF_TWO(temp_out[j], 4)
+ vrshr.s16 q8, q8, #4
+ vrshr.s16 q9, q9, #4
+
+ vld1.32 {d26[0]}, [r1], r2
+ vld1.32 {d26[1]}, [r1], r2
+ vld1.32 {d27[1]}, [r1], r2
+ vld1.32 {d27[0]}, [r1] ; no post-increment
+
+ ; ROUND_POWER_OF_TWO(temp_out[j], 4) + dest[j * dest_stride + i]
+ vaddw.u8 q8, q8, d26
+ vaddw.u8 q9, q9, d27
+
+ ; clip_pixel
+ vqmovun.s16 d26, q8
+ vqmovun.s16 d27, q9
+
+ ; do the stores in reverse order with negative post-increment, by changing
+ ; the sign of the stride
+ rsb r2, r2, #0
+ vst1.32 {d27[0]}, [r1], r2
+ vst1.32 {d27[1]}, [r1], r2
+ vst1.32 {d26[1]}, [r1], r2
+ vst1.32 {d26[0]}, [r1] ; no post-increment
+ bx lr
+ ENDP ; |vp9_short_idct4x4_add_neon|
+
+ END
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