1/* libs/pixelflinger/col32cb16blend.S
2 *
3 * Copyright (C) 2009 The Android Open Source Project
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 *      http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18    .text
19    .align
20
21    .global scanline_col32cb16blend_arm
22
23//
24// This function alpha blends a fixed color into a destination scanline, using
25// the formula:
26//
27//     d = s + (((a + (a >> 7)) * d) >> 8)
28//
29// where d is the destination pixel,
30//       s is the source color,
31//       a is the alpha channel of the source color.
32//
33
34// r0 = destination buffer pointer
35// r1 = color value
36// r2 = count
37
38
39scanline_col32cb16blend_arm:
40    push        {r4-r10, lr}                    // stack ARM regs
41
42    mov         r5, r1, lsr #24                 // shift down alpha
43    mov         r9, #0xff                       // create mask
44    add         r5, r5, r5, lsr #7              // add in top bit
45    rsb         r5, r5, #256                    // invert alpha
46    and         r10, r1, #0xff                  // extract red
47    and         r12, r9, r1, lsr #8             // extract green
48    and         r4, r9, r1, lsr #16             // extract blue
49    mov         r10, r10, lsl #5                // prescale red
50    mov         r12, r12, lsl #6                // prescale green
51    mov         r4, r4, lsl #5                  // prescale blue
52    mov         r9, r9, lsr #2                  // create dest green mask
53
541:
55    ldrh        r8, [r0]                        // load dest pixel
56    subs        r2, r2, #1                      // decrement loop counter
57    mov         r6, r8, lsr #11                 // extract dest red
58    and         r7, r9, r8, lsr #5              // extract dest green
59    and         r8, r8, #0x1f                   // extract dest blue
60
61    smlabb      r6, r6, r5, r10                 // dest red * alpha + src red
62    smlabb      r7, r7, r5, r12                 // dest green * alpha + src green
63    smlabb      r8, r8, r5, r4                  // dest blue * alpha + src blue
64
65    mov         r6, r6, lsr #8                  // shift down red
66    mov         r7, r7, lsr #8                  // shift down green
67    mov         r6, r6, lsl #11                 // shift red into 565
68    orr         r6, r7, lsl #5                  // shift green into 565
69    orr         r6, r8, lsr #8                  // shift blue into 565
70
71    strh        r6, [r0], #2                    // store pixel to dest, update ptr
72    bne         1b                              // if count != 0, loop
73
74    pop         {r4-r10, pc}                    // return
75
76
77
78