--- /dev/null
+;
+; Copyright (c) 2011 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 |vp8_mse16x16_armv6|
+
+ ARM
+
+ AREA ||.text||, CODE, READONLY, ALIGN=2
+
+; r0 unsigned char *src_ptr
+; r1 int source_stride
+; r2 unsigned char *ref_ptr
+; r3 int recon_stride
+; stack unsigned int *sse
+;
+;note: Based on vp8_variance16x16_armv6. In this function, sum is never used.
+; So, we can remove this part of calculation.
+
+|vp8_mse16x16_armv6| PROC
+
+ push {r4-r9, lr}
+ mov r12, #16 ; set loop counter to 16 (=block height)
+
+ mov r4, #0 ; initialize sse = 0
+
+loop
+ ; 1st 4 pixels
+ ldr r5, [r0, #0x0] ; load 4 src pixels
+ ldr r6, [r2, #0x0] ; load 4 ref pixels
+
+ mov lr, #0 ; constant zero
+
+ usub8 r8, r5, r6 ; calculate difference
+ sel r7, r8, lr ; select bytes with positive difference
+ usub8 r9, r6, r5 ; calculate difference with reversed operands
+ sel r8, r9, lr ; select bytes with negative difference
+
+ ; calculate partial sums
+ usad8 r5, r7, lr ; calculate sum of positive differences
+ usad8 r6, r8, lr ; calculate sum of negative differences
+ orr r8, r8, r7 ; differences of all 4 pixels
+
+ ldr r5, [r0, #0x4] ; load 4 src pixels
+
+ ; calculate sse
+ uxtb16 r6, r8 ; byte (two pixels) to halfwords
+ uxtb16 r7, r8, ror #8 ; another two pixels to halfwords
+ smlad r4, r6, r6, r4 ; dual signed multiply, add and accumulate (1)
+
+ ; 2nd 4 pixels
+ ldr r6, [r2, #0x4] ; load 4 ref pixels
+ smlad r4, r7, r7, r4 ; dual signed multiply, add and accumulate (2)
+
+ usub8 r8, r5, r6 ; calculate difference
+ sel r7, r8, lr ; select bytes with positive difference
+ usub8 r9, r6, r5 ; calculate difference with reversed operands
+ sel r8, r9, lr ; select bytes with negative difference
+
+ ; calculate partial sums
+ usad8 r5, r7, lr ; calculate sum of positive differences
+ usad8 r6, r8, lr ; calculate sum of negative differences
+ orr r8, r8, r7 ; differences of all 4 pixels
+ ldr r5, [r0, #0x8] ; load 4 src pixels
+ ; calculate sse
+ uxtb16 r6, r8 ; byte (two pixels) to halfwords
+ uxtb16 r7, r8, ror #8 ; another two pixels to halfwords
+ smlad r4, r6, r6, r4 ; dual signed multiply, add and accumulate (1)
+
+ ; 3rd 4 pixels
+ ldr r6, [r2, #0x8] ; load 4 ref pixels
+ smlad r4, r7, r7, r4 ; dual signed multiply, add and accumulate (2)
+
+ usub8 r8, r5, r6 ; calculate difference
+ sel r7, r8, lr ; select bytes with positive difference
+ usub8 r9, r6, r5 ; calculate difference with reversed operands
+ sel r8, r9, lr ; select bytes with negative difference
+
+ ; calculate partial sums
+ usad8 r5, r7, lr ; calculate sum of positive differences
+ usad8 r6, r8, lr ; calculate sum of negative differences
+ orr r8, r8, r7 ; differences of all 4 pixels
+
+ ldr r5, [r0, #0xc] ; load 4 src pixels
+
+ ; calculate sse
+ uxtb16 r6, r8 ; byte (two pixels) to halfwords
+ uxtb16 r7, r8, ror #8 ; another two pixels to halfwords
+ smlad r4, r6, r6, r4 ; dual signed multiply, add and accumulate (1)
+
+ ; 4th 4 pixels
+ ldr r6, [r2, #0xc] ; load 4 ref pixels
+ smlad r4, r7, r7, r4 ; dual signed multiply, add and accumulate (2)
+
+ usub8 r8, r5, r6 ; calculate difference
+ add r0, r0, r1 ; set src_ptr to next row
+ sel r7, r8, lr ; select bytes with positive difference
+ usub8 r9, r6, r5 ; calculate difference with reversed operands
+ add r2, r2, r3 ; set dst_ptr to next row
+ sel r8, r9, lr ; select bytes with negative difference
+
+ ; calculate partial sums
+ usad8 r5, r7, lr ; calculate sum of positive differences
+ usad8 r6, r8, lr ; calculate sum of negative differences
+ orr r8, r8, r7 ; differences of all 4 pixels
+
+ subs r12, r12, #1 ; next row
+
+ ; calculate sse
+ uxtb16 r6, r8 ; byte (two pixels) to halfwords
+ uxtb16 r7, r8, ror #8 ; another two pixels to halfwords
+ smlad r4, r6, r6, r4 ; dual signed multiply, add and accumulate (1)
+ smlad r4, r7, r7, r4 ; dual signed multiply, add and accumulate (2)
+
+ bne loop
+
+ ; return stuff
+ ldr r1, [sp, #28] ; get address of sse
+ mov r0, r4 ; return sse
+ str r4, [r1] ; store sse
+
+ pop {r4-r9, pc}
+
+ ENDP
+
+ END