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/* libs/pixelflinger/col32cb16blend_neon.S
*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
.text
.balign 4
.global scanline_col32cb16blend_neon
//
// This function alpha blends a fixed color into a destination scanline, using
// the formula:
//
// d = s + (((a + (a >> 7)) * d) >> 8)
//
// where d is the destination pixel,
// s is the source color,
// a is the alpha channel of the source color.
//
// The NEON implementation processes 16 pixels per iteration. The remaining 0 - 15
// pixels are processed in ARM code.
//
// r0 = destination buffer pointer
// r1 = color pointer
// r2 = count
scanline_col32cb16blend_neon:
push {r4-r11, lr} // stack ARM regs
vmov.u16 q15, #256 // create alpha constant
movs r3, r2, lsr #4 // calc. sixteens iterations
vmov.u16 q14, #0x1f // create blue mask
beq 2f // if r3 == 0, branch to singles
vld4.8 {d0[], d2[], d4[], d6[]}, [r1] // load color into four registers
// split and duplicate them, such that
// d0 = 8 equal red values
// d2 = 8 equal green values
// d4 = 8 equal blue values
// d6 = 8 equal alpha values
vshll.u8 q0, d0, #5 // shift up red and widen
vshll.u8 q1, d2, #6 // shift up green and widen
vshll.u8 q2, d4, #5 // shift up blue and widen
vshr.u8 d7, d6, #7 // extract top bit of alpha
vaddl.u8 q3, d6, d7 // add top bit into alpha
vsub.u16 q3, q15, q3 // invert alpha
1:
// This loop processes 16 pixels per iteration. In the comments, references to
// the first eight pixels are suffixed with "0" (red0, green0, blue0),
// the second eight are suffixed "1".
// q8 = dst red0
// q9 = dst green0
// q10 = dst blue0
// q13 = dst red1
// q12 = dst green1
// q11 = dst blue1
vld1.16 {d20, d21, d22, d23}, [r0] // load 16 dest pixels
vshr.u16 q8, q10, #11 // shift dst red0 to low 5 bits
pld [r0, #63] // preload next dest pixels
vshl.u16 q9, q10, #5 // shift dst green0 to top 6 bits
vand q10, q10, q14 // extract dst blue0
vshr.u16 q9, q9, #10 // shift dst green0 to low 6 bits
vmul.u16 q8, q8, q3 // multiply dst red0 by src alpha
vshl.u16 q12, q11, #5 // shift dst green1 to top 6 bits
vmul.u16 q9, q9, q3 // multiply dst green0 by src alpha
vshr.u16 q13, q11, #11 // shift dst red1 to low 5 bits
vmul.u16 q10, q10, q3 // multiply dst blue0 by src alpha
vshr.u16 q12, q12, #10 // shift dst green1 to low 6 bits
vand q11, q11, q14 // extract dst blue1
vadd.u16 q8, q8, q0 // add src red to dst red0
vmul.u16 q13, q13, q3 // multiply dst red1 by src alpha
vadd.u16 q9, q9, q1 // add src green to dst green0
vmul.u16 q12, q12, q3 // multiply dst green1 by src alpha
vadd.u16 q10, q10, q2 // add src blue to dst blue0
vmul.u16 q11, q11, q3 // multiply dst blue1 by src alpha
vshr.u16 q8, q8, #8 // shift down red0
vadd.u16 q13, q13, q0 // add src red to dst red1
vshr.u16 q9, q9, #8 // shift down green0
vadd.u16 q12, q12, q1 // add src green to dst green1
vshr.u16 q10, q10, #8 // shift down blue0
vadd.u16 q11, q11, q2 // add src blue to dst blue1
vsli.u16 q10, q9, #5 // shift & insert green0 into blue0
vshr.u16 q13, q13, #8 // shift down red1
vsli.u16 q10, q8, #11 // shift & insert red0 into blue0
vshr.u16 q12, q12, #8 // shift down green1
vshr.u16 q11, q11, #8 // shift down blue1
subs r3, r3, #1 // decrement loop counter
vsli.u16 q11, q12, #5 // shift & insert green1 into blue1
vsli.u16 q11, q13, #11 // shift & insert red1 into blue1
vst1.16 {d20, d21, d22, d23}, [r0]! // write 16 pixels back to dst
bne 1b // if count != 0, loop
2:
ands r3, r2, #15 // calc. single iterations
beq 4f // if r3 == 0, exit
ldr r4, [r1] // load source color
mov r5, r4, lsr #24 // shift down alpha
add r5, r5, r5, lsr #7 // add in top bit
rsb r5, r5, #256 // invert alpha
and r11, r4, #0xff // extract red
ubfx r12, r4, #8, #8 // extract green
ubfx r4, r4, #16, #8 // extract blue
mov r11, r11, lsl #5 // prescale red
mov r12, r12, lsl #6 // prescale green
mov r4, r4, lsl #5 // prescale blue
3:
ldrh r8, [r0] // load dest pixel
subs r3, r3, #1 // decrement loop counter
mov r6, r8, lsr #11 // extract dest red
ubfx r7, r8, #5, #6 // extract dest green
and r8, r8, #0x1f // extract dest blue
smlabb r6, r6, r5, r11 // dest red * alpha + src red
smlabb r7, r7, r5, r12 // dest green * alpha + src green
smlabb r8, r8, r5, r4 // dest blue * alpha + src blue
mov r6, r6, lsr #8 // shift down red
mov r7, r7, lsr #8 // shift down green
mov r6, r6, lsl #11 // shift red into 565
orr r6, r7, lsl #5 // shift green into 565
orr r6, r8, lsr #8 // shift blue into 565
strh r6, [r0], #2 // store pixel to dest, update ptr
bne 3b // if count != 0, loop
4:
pop {r4-r11, pc} // return
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