dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2024-11-20 04:18:26 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

Merge "NEON TransformOne"

Browse Source
This commit is contained in:
Johann 2012-01-26 11:38:16 -08:00 committed by Gerrit Code Review
commit cab8d4dc22
1 changed files with 161 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

163
src/dsp/dec_neon.c
View File

@ -1,4 +1,4 @@
// Copyright 2011 Google Inc. All Rights Reserved.
// Copyright 2012 Google Inc. All Rights Reserved.
//
// This code is licensed under the same terms as WebM:
// Software License Agreement: http://www.webmproject.org/license/software/
@ -7,7 +7,8 @@
//
// ARM NEON version of dsp functions and loop filtering.
//
// Author: somnath@google.com (Somnath Banerjee)
// Authors: Somnath Banerjee (somnath@google.com)
// Johann Koenig (johannkoenig@google.com)
#if defined(__GNUC__) && defined(__ARM_NEON__)
@ -152,9 +153,167 @@ static void SimpleHFilter16iNEON(uint8_t* p, int stride, int thresh) {
}
}
static void TransformOneNEON(const int16_t *in, uint8_t *dst) {
const int kBPS = BPS;
const int16_t constants[] = {20091, 17734, 0, 0};
/* kC1, kC2. Padded because vld1.16 loads 8 bytes
* Technically these are unsigned but vqdmulh is only available in signed.
* vqdmulh returns high half (effectively >> 16) but also doubles the value,
* changing the >> 16 to >> 15 and requiring an additional >> 1.
* We use this to our advantage with kC2. The canonical value is 35468.
* However, the high bit is set so treating it as signed will give incorrect
* results. We avoid this by down shifting by 1 here to clear the highest bit.
* Combined with the doubling effect of vqdmulh we get >> 16.
* This can not be applied to kC1 because the lowest bit is set. Down shifting
* the constant would reduce precision.
*/
/* libwebp uses a trick to avoid some extra addition that libvpx does.
* Instead of:
* temp2 = ip[12] + ((ip[12] * cospi8sqrt2minus1) >> 16);
* libwebp adds 1 << 16 to cospi8sqrt2minus1 (kC1). However, this causes the
* same issue with kC1 and vqdmulh that we work around by down shifting kC2
*/
/* Adapted from libvpx: vp8/common/arm/neon/shortidct4x4llm_neon.asm */
__asm__ volatile (
"vld1.16 {q1, q2}, [%[in]] \n"
"vld1.16 {d0}, [%[constants]] \n"
/* d2: in[0]
* d3: in[8]
* d4: in[4]
* d5: in[12]
*/
"vswp d3, d4 \n"
/* q8 = {in[4], in[12]} * kC1 * 2 >> 16
* q9 = {in[4], in[12]} * kC2 >> 16
*/
"vqdmulh.s16 q8, q2, d0[0] \n"
"vqdmulh.s16 q9, q2, d0[1] \n"
/* d22 = a = in[0] + in[8]
* d23 = b = in[0] - in[8]
*/
"vqadd.s16 d22, d2, d3 \n"
"vqsub.s16 d23, d2, d3 \n"
/* The multiplication should be x * kC1 >> 16
* However, with vqdmulh we get x * kC1 * 2 >> 16
* (multiply, double, return high half)
* We avoided this in kC2 by pre-shifting the constant.
* q8 = in[4]/[12] * kC1 >> 16
*/
"vshr.s16 q8, q8, #1 \n"
/* Add {in[4], in[12]} back after the multiplication. This is handled by
* adding 1 << 16 to kC1 in the libwebp C code.
*/
"vqadd.s16 q8, q2, q8 \n"
/* d20 = c = in[4]*kC2 - in[12]*kC1
* d21 = d = in[4]*kC1 + in[12]*kC2
*/
"vqsub.s16 d20, d18, d17 \n"
"vqadd.s16 d21, d19, d16 \n"
/* d2 = tmp[0] = a + d
* d3 = tmp[1] = b + c
* d4 = tmp[2] = b - c
* d5 = tmp[3] = a - d
*/
"vqadd.s16 d2, d22, d21 \n"
"vqadd.s16 d3, d23, d20 \n"
"vqsub.s16 d4, d23, d20 \n"
"vqsub.s16 d5, d22, d21 \n"
"vzip.16 q1, q2 \n"
"vzip.16 q1, q2 \n"
"vswp d3, d4 \n"
/* q8 = {tmp[4], tmp[12]} * kC1 * 2 >> 16
* q9 = {tmp[4], tmp[12]} * kC2 >> 16
*/
"vqdmulh.s16 q8, q2, d0[0] \n"
"vqdmulh.s16 q9, q2, d0[1] \n"
/* d22 = a = tmp[0] + tmp[8]
* d23 = b = tmp[0] - tmp[8]
*/
"vqadd.s16 d22, d2, d3 \n"
"vqsub.s16 d23, d2, d3 \n"
/* See long winded explanations prior */
"vshr.s16 q8, q8, #1 \n"
"vqadd.s16 q8, q2, q8 \n"
/* d20 = c = in[4]*kC2 - in[12]*kC1
* d21 = d = in[4]*kC1 + in[12]*kC2
*/
"vqsub.s16 d20, d18, d17 \n"
"vqadd.s16 d21, d19, d16 \n"
/* d2 = tmp[0] = a + d
* d3 = tmp[1] = b + c
* d4 = tmp[2] = b - c
* d5 = tmp[3] = a - d
*/
"vqadd.s16 d2, d22, d21 \n"
"vqadd.s16 d3, d23, d20 \n"
"vqsub.s16 d4, d23, d20 \n"
"vqsub.s16 d5, d22, d21 \n"
"vld1.32 d6[0], [%[dst]], %[kBPS] \n"
"vld1.32 d6[1], [%[dst]], %[kBPS] \n"
"vld1.32 d7[0], [%[dst]], %[kBPS] \n"
"vld1.32 d7[1], [%[dst]], %[kBPS] \n"
"sub %[dst], %[dst], %[kBPS], lsl #2 \n"
/* (val) + 4 >> 3 */
"vrshr.s16 d2, d2, #3 \n"
"vrshr.s16 d3, d3, #3 \n"
"vrshr.s16 d4, d4, #3 \n"
"vrshr.s16 d5, d5, #3 \n"
"vzip.16 q1, q2 \n"
"vzip.16 q1, q2 \n"
/* Must accumulate before saturating */
"vmovl.u8 q8, d6 \n"
"vmovl.u8 q9, d7 \n"
"vqadd.s16 q1, q1, q8 \n"
"vqadd.s16 q2, q2, q9 \n"
"vqmovun.s16 d0, q1 \n"
"vqmovun.s16 d1, q2 \n"
"vst1.32 d0[0], [%[dst]], %[kBPS] \n"
"vst1.32 d0[1], [%[dst]], %[kBPS] \n"
"vst1.32 d1[0], [%[dst]], %[kBPS] \n"
"vst1.32 d1[1], [%[dst]] \n"
: [in] "+r"(in), [dst] "+r"(dst) /* modified registers */
: [kBPS] "r"(kBPS), [constants] "r"(constants) /* constants */
: "memory", "q0", "q1", "q2", "q8", "q9", "q10", "q11" /* clobbered */
);
}
static void TransformTwoNEON(const int16_t* in, uint8_t* dst, int do_two) {
TransformOneNEON(in, dst);
if (do_two) {
TransformOneNEON(in + 16, dst + 4);
}
}
extern void VP8DspInitNEON(void);
void VP8DspInitNEON(void) {
VP8Transform = TransformTwoNEON;
VP8SimpleVFilter16 = SimpleVFilter16NEON;
VP8SimpleHFilter16 = SimpleHFilter16NEON;
VP8SimpleVFilter16i = SimpleVFilter16iNEON;