/ *
* simple_ i d c t _ a r m . S
* Copyright ( C ) 2 0 0 2 F r e d e r i c ' d i l b ' B o u l a y .
*
* Author : Frederic B o u l a y < d i l b @handhelds.org>
*
* The f u n c t i o n d e f i n e d i n t h i s f i l e i s d e r i v e d f r o m t h e s i m p l e _ i d c t f u n c t i o n
* from t h e l i b a v c o d e c l i b r a r y p a r t o f t h e F F m p e g p r o j e c t .
*
* This f i l e i s p a r t o f F F m p e g .
*
* FFmpeg i s f r e e s o f t w a r e ; you can redistribute it and/or
* modify i t u n d e r t h e t e r m s o f t h e G N U L e s s e r G e n e r a l P u b l i c
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* version 2 . 1 o f t h e L i c e n s e , o r ( a t y o u r o p t i o n ) a n y l a t e r v e r s i o n .
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* /
/* useful constants for the algorithm, they are save in __constant_ptr__ at */
/* the end of the source code.*/
# define W 1 2 2 7 2 5
# define W 2 2 1 4 0 7
# define W 3 1 9 2 6 6
# define W 4 1 6 3 8 3
# define W 5 1 2 8 7 3
# define W 6 8 8 6 7
# define W 7 4 5 2 0
# define M A S K _ M S H W 0 x F F F F 0 0 0 0
/* offsets of the constants in the vector */
# define o f f W 1 0
# define o f f W 2 4
# define o f f W 3 8
# define o f f W 4 1 2
# define o f f W 5 1 6
# define o f f W 6 2 0
# define o f f W 7 2 4
# define o f f M A S K _ M S H W 2 8
# define R O W _ S H I F T 1 1
# define R O W _ S H I F T 2 M S H W ( 1 6 - 1 1 )
# define C O L _ S H I F T 2 0
# define R O W _ S H I F T E D _ 1 1 0 2 4 / * 1 < < ( R O W _ S H I F T - 1 ) * /
# define C O L _ S H I F T E D _ 1 5 2 4 2 8 8 / * 1 < < ( C O L _ S H I F T - 1 ) * /
.text
.align
.global simple_idct_ARM
simple_idct_ARM :
@@ void simple_idct_ARM(int16_t *block)
@@ save stack for reg needed (take all of them),
@@ R0-R3 are scratch regs, so no need to save them, but R0 contains the pointer to block
@@ so it must not be overwritten, if it is not saved!!
@@ R12 is another scratch register, so it should not be saved too
@@ save all registers
stmfd s p ! , { r4 - r11 , r14 } @ R14 is also called LR
@@ at this point, R0=block, other registers are free.
add r14 , r0 , #112 @ R14=&block[8*7], better start from the last row, and decrease the value until row=0, i.e. R12=block.
add r12 , p c , #( _ _ c o n s t a n t _ p t r _ _ - . - 8 ) @ R12=__constant_ptr__, the vector containing the constants, probably not necessary to reserve a register for it
@@ add 2 temporary variables in the stack: R0 and R14
sub s p , s p , #8 @ allow 2 local variables
str r0 , [ s p , #0 ] @ save block in sp[0]
@@ stack status
@@ sp+4 free
@@ sp+0 R0 (block)
@@ at this point, R0=block, R14=&block[56], R12=__const_ptr_, R1-R11 free
__row_loop :
@@ read the row and check if it is null, almost null, or not, according to strongarm specs, it is not necessary to optimise ldr accesses (i.e. split 32bits in 2 16bits words), at least it gives more usable registers :)
ldr r1 , [ r14 , #0 ] @ R1=(int32)(R12)[0]=ROWr32[0] (relative row cast to a 32b pointer)
ldr r2 , [ r14 , #4 ] @ R2=(int32)(R12)[1]=ROWr32[1]
ldr r3 , [ r14 , #8 ] @ R3=ROWr32[2]
ldr r4 , [ r14 , #12 ] @ R4=ROWr32[3]
@@ check if the words are null, if all of them are null, then proceed with next row (branch __end_row_loop),
@@ if ROWr16[0] is the only one not null, then proceed with this special case (branch __almost_empty_row)
@@ else follow the complete algorithm.
@@ at this point, R0=block, R14=&block[n], R12=__const_ptr_, R1=ROWr32[0], R2=ROWr32[1],
@@ R3=ROWr32[2], R4=ROWr32[3], R5-R11 free
orr r5 , r4 , r3 @ R5=R4 | R3
orr r5 , r5 , r2 @ R5=R4 | R3 | R2
orrs r6 , r5 , r1 @ Test R5 | R1 (the aim is to check if everything is null)
beq _ _ e n d _ r o w _ l o o p
mov r7 , r1 , a s r #16 @ R7=R1>>16=ROWr16[1] (evaluate it now, as it could be useful later)
ldrsh r6 , [ r14 , #0 ] @ R6=ROWr16[0]
orrs r5 , r5 , r7 @ R5=R4 | R3 | R2 | R7
beq _ _ a l m o s t _ e m p t y _ r o w
__b_evaluation :
@@ at this point, R0=block (temp), R1(free), R2=ROWr32[1], R3=ROWr32[2], R4=ROWr32[3],
@@ R5=(temp), R6=ROWr16[0], R7=ROWr16[1], R8-R11 free,
@@ R12=__const_ptr_, R14=&block[n]
@@ to save some registers/calls, proceed with b0-b3 first, followed by a0-a3
@@ MUL16(b0, W1, row[1]);
@@ MUL16(b1, W3, row[1]);
@@ MUL16(b2, W5, row[1]);
@@ MUL16(b3, W7, row[1]);
@@ MAC16(b0, W3, row[3]);
@@ MAC16(b1, -W7, row[3]);
@@ MAC16(b2, -W1, row[3]);
@@ MAC16(b3, -W5, row[3]);
ldr r8 , [ r12 , #o f f W 1 ] @ R8=W1
mov r2 , r2 , a s r #16 @ R2=ROWr16[3]
mul r0 , r8 , r7 @ R0=W1*ROWr16[1]=b0 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
ldr r9 , [ r12 , #o f f W 3 ] @ R9=W3
ldr r10 , [ r12 , #o f f W 5 ] @ R10=W5
mul r1 , r9 , r7 @ R1=W3*ROWr16[1]=b1 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
ldr r11 , [ r12 , #o f f W 7 ] @ R11=W7
mul r5 , r10 , r7 @ R5=W5*ROWr16[1]=b2 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
mul r7 , r11 , r7 @ R7=W7*ROWr16[1]=b3 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
teq r2 , #0 @ if null avoid muls
mlane r0 , r9 , r2 , r0 @ R0+=W3*ROWr16[3]=b0 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
rsbne r2 , r2 , #0 @ R2=-ROWr16[3]
mlane r1 , r11 , r2 , r1 @ R1-=W7*ROWr16[3]=b1 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
mlane r5 , r8 , r2 , r5 @ R5-=W1*ROWr16[3]=b2 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
mlane r7 , r10 , r2 , r7 @ R7-=W5*ROWr16[3]=b3 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
@@ at this point, R0=b0, R1=b1, R2 (free), R3=ROWr32[2], R4=ROWr32[3],
@@ R5=b2, R6=ROWr16[0], R7=b3, R8=W1, R9=W3, R10=W5, R11=W7,
@@ R12=__const_ptr_, R14=&block[n]
@@ temp = ((uint32_t*)row)[2] | ((uint32_t*)row)[3];
@@ if (temp != 0) {}
orrs r2 , r3 , r4 @ R2=ROWr32[2] | ROWr32[3]
beq _ _ e n d _ b _ e v a l u a t i o n
@@ at this point, R0=b0, R1=b1, R2 (free), R3=ROWr32[2], R4=ROWr32[3],
@@ R5=b2, R6=ROWr16[0], R7=b3, R8=W1, R9=W3, R10=W5, R11=W7,
@@ R12=__const_ptr_, R14=&block[n]
@@ MAC16(b0, W5, row[5]);
@@ MAC16(b2, W7, row[5]);
@@ MAC16(b3, W3, row[5]);
@@ MAC16(b1, -W1, row[5]);
@@ MAC16(b0, W7, row[7]);
@@ MAC16(b2, W3, row[7]);
@@ MAC16(b3, -W1, row[7]);
@@ MAC16(b1, -W5, row[7]);
mov r3 , r3 , a s r #16 @ R3=ROWr16[5]
teq r3 , #0 @ if null avoid muls
mlane r0 , r10 , r3 , r0 @ R0+=W5*ROWr16[5]=b0
mov r4 , r4 , a s r #16 @ R4=ROWr16[7]
mlane r5 , r11 , r3 , r5 @ R5+=W7*ROWr16[5]=b2
mlane r7 , r9 , r3 , r7 @ R7+=W3*ROWr16[5]=b3
rsbne r3 , r3 , #0 @ R3=-ROWr16[5]
mlane r1 , r8 , r3 , r1 @ R7-=W1*ROWr16[5]=b1
@@ R3 is free now
teq r4 , #0 @ if null avoid muls
mlane r0 , r11 , r4 , r0 @ R0+=W7*ROWr16[7]=b0
mlane r5 , r9 , r4 , r5 @ R5+=W3*ROWr16[7]=b2
rsbne r4 , r4 , #0 @ R4=-ROWr16[7]
mlane r7 , r8 , r4 , r7 @ R7-=W1*ROWr16[7]=b3
mlane r1 , r10 , r4 , r1 @ R1-=W5*ROWr16[7]=b1
@@ R4 is free now
__end_b_evaluation :
@@ at this point, R0=b0, R1=b1, R2=ROWr32[2] | ROWr32[3] (tmp), R3 (free), R4 (free),
@@ R5=b2, R6=ROWr16[0], R7=b3, R8 (free), R9 (free), R10 (free), R11 (free),
@@ R12=__const_ptr_, R14=&block[n]
__a_evaluation :
@@ a0 = (W4 * row[0]) + (1 << (ROW_SHIFT - 1));
@@ a1 = a0 + W6 * row[2];
@@ a2 = a0 - W6 * row[2];
@@ a3 = a0 - W2 * row[2];
@@ a0 = a0 + W2 * row[2];
ldr r9 , [ r12 , #o f f W 4 ] @ R9=W4
mul r6 , r9 , r6 @ R6=W4*ROWr16[0]
ldr r10 , [ r12 , #o f f W 6 ] @ R10=W6
ldrsh r4 , [ r14 , #4 ] @ R4=ROWr16[2] (a3 not defined yet)
add r6 , r6 , #R O W _ S H I F T E D _ 1 @ R6=W4*ROWr16[0] + 1<<(ROW_SHIFT-1) (a0)
mul r11 , r10 , r4 @ R11=W6*ROWr16[2]
ldr r8 , [ r12 , #o f f W 2 ] @ R8=W2
sub r3 , r6 , r11 @ R3=a0-W6*ROWr16[2] (a2)
@@ temp = ((uint32_t*)row)[2] | ((uint32_t*)row)[3];
@@ if (temp != 0) {}
teq r2 , #0
beq _ _ e n d _ b e f _ a _ e v a l u a t i o n
add r2 , r6 , r11 @ R2=a0+W6*ROWr16[2] (a1)
mul r11 , r8 , r4 @ R11=W2*ROWr16[2]
sub r4 , r6 , r11 @ R4=a0-W2*ROWr16[2] (a3)
add r6 , r6 , r11 @ R6=a0+W2*ROWr16[2] (a0)
@@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3,
@@ R5=b2, R6=a0, R7=b3, R8=W2, R9=W4, R10=W6, R11 (free),
@@ R12=__const_ptr_, R14=&block[n]
@@ a0 += W4*row[4]
@@ a1 -= W4*row[4]
@@ a2 -= W4*row[4]
@@ a3 += W4*row[4]
ldrsh r11 , [ r14 , #8 ] @ R11=ROWr16[4]
teq r11 , #0 @ if null avoid muls
mulne r11 , r9 , r11 @ R11=W4*ROWr16[4]
@@ R9 is free now
ldrsh r9 , [ r14 , #12 ] @ R9=ROWr16[6]
addne r6 , r6 , r11 @ R6+=W4*ROWr16[4] (a0)
subne r2 , r2 , r11 @ R2-=W4*ROWr16[4] (a1)
subne r3 , r3 , r11 @ R3-=W4*ROWr16[4] (a2)
addne r4 , r4 , r11 @ R4+=W4*ROWr16[4] (a3)
@@ W6 alone is no more useful, save W2*ROWr16[6] in it instead
teq r9 , #0 @ if null avoid muls
mulne r11 , r10 , r9 @ R11=W6*ROWr16[6]
addne r6 , r6 , r11 @ R6+=W6*ROWr16[6] (a0)
mulne r10 , r8 , r9 @ R10=W2*ROWr16[6]
@@ a0 += W6*row[6];
@@ a3 -= W6*row[6];
@@ a1 -= W2*row[6];
@@ a2 += W2*row[6];
subne r4 , r4 , r11 @ R4-=W6*ROWr16[6] (a3)
subne r2 , r2 , r10 @ R2-=W2*ROWr16[6] (a1)
addne r3 , r3 , r10 @ R3+=W2*ROWr16[6] (a2)
__end_a_evaluation :
@@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3,
@@ R5=b2, R6=a0, R7=b3, R8 (free), R9 (free), R10 (free), R11 (free),
@@ R12=__const_ptr_, R14=&block[n]
@@ row[0] = (a0 + b0) >> ROW_SHIFT;
@@ row[1] = (a1 + b1) >> ROW_SHIFT;
@@ row[2] = (a2 + b2) >> ROW_SHIFT;
@@ row[3] = (a3 + b3) >> ROW_SHIFT;
@@ row[4] = (a3 - b3) >> ROW_SHIFT;
@@ row[5] = (a2 - b2) >> ROW_SHIFT;
@@ row[6] = (a1 - b1) >> ROW_SHIFT;
@@ row[7] = (a0 - b0) >> ROW_SHIFT;
add r8 , r6 , r0 @ R8=a0+b0
add r9 , r2 , r1 @ R9=a1+b1
@@ put 2 16 bits half-words in a 32bits word
@@ ROWr32[0]=ROWr16[0] | (ROWr16[1]<<16) (only Little Endian compliant then!!!)
ldr r10 , [ r12 , #o f f M A S K _ M S H W ] @ R 10 =0xFFFF0000
and r9 , r10 , r9 , l s l #R O W _ S H I F T 2 M S H W @ R9=0xFFFF0000 & ((a1+b1)<<5)
mvn r11 , r10 @ R11= NOT R10= 0x0000FFFF
and r8 , r11 , r8 , a s r #R O W _ S H I F T @ R 8 =0x0000FFFF & ( ( a0 + b0 ) > > 1 1 )
orr r8 , r8 , r9
str r8 , [ r14 , #0 ]
add r8 , r3 , r5 @ R8=a2+b2
add r9 , r4 , r7 @ R9=a3+b3
and r9 , r10 , r9 , l s l #R O W _ S H I F T 2 M S H W @ R9=0xFFFF0000 & ((a3+b3)<<5)
and r8 , r11 , r8 , a s r #R O W _ S H I F T @ R 8 =0x0000FFFF & ( ( a2 + b2 ) > > 1 1 )
orr r8 , r8 , r9
str r8 , [ r14 , #4 ]
sub r8 , r4 , r7 @ R8=a3-b3
sub r9 , r3 , r5 @ R9=a2-b2
and r9 , r10 , r9 , l s l #R O W _ S H I F T 2 M S H W @ R9=0xFFFF0000 & ((a2-b2)<<5)
and r8 , r11 , r8 , a s r #R O W _ S H I F T @ R 8 =0x0000FFFF & ( ( a3 - b3 ) > > 1 1 )
orr r8 , r8 , r9
str r8 , [ r14 , #8 ]
sub r8 , r2 , r1 @ R8=a1-b1
sub r9 , r6 , r0 @ R9=a0-b0
and r9 , r10 , r9 , l s l #R O W _ S H I F T 2 M S H W @ R9=0xFFFF0000 & ((a0-b0)<<5)
and r8 , r11 , r8 , a s r #R O W _ S H I F T @ R 8 =0x0000FFFF & ( ( a1 - b1 ) > > 1 1 )
orr r8 , r8 , r9
str r8 , [ r14 , #12 ]
bal _ _ e n d _ r o w _ l o o p
__almost_empty_row :
@@ the row was empty, except ROWr16[0], now, management of this special case
@@ at this point, R0=block, R14=&block[n], R12=__const_ptr_, R1=ROWr32[0], R2=ROWr32[1],
@@ R3=ROWr32[2], R4=ROWr32[3], R5=(temp), R6=ROWr16[0], R7=ROWr16[1],
@@ R8=0xFFFF (temp), R9-R11 free
mov r8 , #0x10000 @ R8=0xFFFF (2 steps needed!) it saves a ldr call (because of delay run).
sub r8 , r8 , #1 @ R8 is now ready.
and r5 , r8 , r6 , l s l #3 @ R5=R8 & (R6<<3)= (ROWr16[0]<<3) & 0xFFFF
orr r5 , r5 , r5 , l s l #16 @ R5=R5 | (R5<<16)
str r5 , [ r14 , #0 ] @ R14[0]=ROWr32[0]=R5
str r5 , [ r14 , #4 ] @ R14[4]=ROWr32[1]=R5
str r5 , [ r14 , #8 ] @ R14[8]=ROWr32[2]=R5
str r5 , [ r14 , #12 ] @ R14[12]=ROWr32[3]=R5
__end_row_loop :
@@ at this point, R0-R11 (free)
@@ R12=__const_ptr_, R14=&block[n]
ldr r0 , [ s p , #0 ] @ R0=block
teq r0 , r14 @ compare current &block[8*n] to block, when block is reached, the loop is finished.
sub r14 , r14 , #16
bne _ _ r o w _ l o o p
@@ at this point, R0=block, R1-R11 (free)
@@ R12=__const_ptr_, R14=&block[n]
add r14 , r0 , #14 @ R14=&block[7], better start from the last col, and decrease the value until col=0, i.e. R14=block.
__col_loop :
__b_evaluation2 :
@@ at this point, R0=block (temp), R1-R11 (free)
@@ R12=__const_ptr_, R14=&block[n]
@@ proceed with b0-b3 first, followed by a0-a3
@@ MUL16(b0, W1, col[8x1]);
@@ MUL16(b1, W3, col[8x1]);
@@ MUL16(b2, W5, col[8x1]);
@@ MUL16(b3, W7, col[8x1]);
@@ MAC16(b0, W3, col[8x3]);
@@ MAC16(b1, -W7, col[8x3]);
@@ MAC16(b2, -W1, col[8x3]);
@@ MAC16(b3, -W5, col[8x3]);
ldr r8 , [ r12 , #o f f W 1 ] @ R8=W1
ldrsh r7 , [ r14 , #16 ]
mul r0 , r8 , r7 @ R0=W1*ROWr16[1]=b0 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
ldr r9 , [ r12 , #o f f W 3 ] @ R9=W3
ldr r10 , [ r12 , #o f f W 5 ] @ R10=W5
mul r1 , r9 , r7 @ R1=W3*ROWr16[1]=b1 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
ldr r11 , [ r12 , #o f f W 7 ] @ R11=W7
mul r5 , r10 , r7 @ R5=W5*ROWr16[1]=b2 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
ldrsh r2 , [ r14 , #48 ]
mul r7 , r11 , r7 @ R7=W7*ROWr16[1]=b3 (ROWr16[1] must be the second arg, to have the possibility to save 1 cycle)
teq r2 , #0 @ if 0, then avoid muls
mlane r0 , r9 , r2 , r0 @ R0+=W3*ROWr16[3]=b0 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
rsbne r2 , r2 , #0 @ R2=-ROWr16[3]
mlane r1 , r11 , r2 , r1 @ R1-=W7*ROWr16[3]=b1 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
mlane r5 , r8 , r2 , r5 @ R5-=W1*ROWr16[3]=b2 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
mlane r7 , r10 , r2 , r7 @ R7-=W5*ROWr16[3]=b3 (ROWr16[3] must be the second arg, to have the possibility to save 1 cycle)
@@ at this point, R0=b0, R1=b1, R2 (free), R3 (free), R4 (free),
@@ R5=b2, R6 (free), R7=b3, R8=W1, R9=W3, R10=W5, R11=W7,
@@ R12=__const_ptr_, R14=&block[n]
@@ MAC16(b0, W5, col[5x8]);
@@ MAC16(b2, W7, col[5x8]);
@@ MAC16(b3, W3, col[5x8]);
@@ MAC16(b1, -W1, col[5x8]);
@@ MAC16(b0, W7, col[7x8]);
@@ MAC16(b2, W3, col[7x8]);
@@ MAC16(b3, -W1, col[7x8]);
@@ MAC16(b1, -W5, col[7x8]);
ldrsh r3 , [ r14 , #80 ] @ R3=COLr16[5x8]
teq r3 , #0 @ if 0 then avoid muls
mlane r0 , r10 , r3 , r0 @ R0+=W5*ROWr16[5x8]=b0
mlane r5 , r11 , r3 , r5 @ R5+=W7*ROWr16[5x8]=b2
mlane r7 , r9 , r3 , r7 @ R7+=W3*ROWr16[5x8]=b3
rsbne r3 , r3 , #0 @ R3=-ROWr16[5x8]
ldrsh r4 , [ r14 , #112 ] @ R4=COLr16[7x8]
mlane r1 , r8 , r3 , r1 @ R7-=W1*ROWr16[5x8]=b1
@@ R3 is free now
teq r4 , #0 @ if 0 then avoid muls
mlane r0 , r11 , r4 , r0 @ R0+=W7*ROWr16[7x8]=b0
mlane r5 , r9 , r4 , r5 @ R5+=W3*ROWr16[7x8]=b2
rsbne r4 , r4 , #0 @ R4=-ROWr16[7x8]
mlane r7 , r8 , r4 , r7 @ R7-=W1*ROWr16[7x8]=b3
mlane r1 , r10 , r4 , r1 @ R1-=W5*ROWr16[7x8]=b1
@@ R4 is free now
__end_b_evaluation2 :
@@ at this point, R0=b0, R1=b1, R2 (free), R3 (free), R4 (free),
@@ R5=b2, R6 (free), R7=b3, R8 (free), R9 (free), R10 (free), R11 (free),
@@ R12=__const_ptr_, R14=&block[n]
__a_evaluation2 :
@@ a0 = (W4 * col[8x0]) + (1 << (COL_SHIFT - 1));
@@ a1 = a0 + W6 * row[2];
@@ a2 = a0 - W6 * row[2];
@@ a3 = a0 - W2 * row[2];
@@ a0 = a0 + W2 * row[2];
ldrsh r6 , [ r14 , #0 ]
ldr r9 , [ r12 , #o f f W 4 ] @ R9=W4
mul r6 , r9 , r6 @ R6=W4*ROWr16[0]
ldr r10 , [ r12 , #o f f W 6 ] @ R10=W6
ldrsh r4 , [ r14 , #32 ] @ R4=ROWr16[2] (a3 not defined yet)
add r6 , r6 , #C O L _ S H I F T E D _ 1 @ R6=W4*ROWr16[0] + 1<<(COL_SHIFT-1) (a0)
mul r11 , r10 , r4 @ R11=W6*ROWr16[2]
ldr r8 , [ r12 , #o f f W 2 ] @ R8=W2
add r2 , r6 , r11 @ R2=a0+W6*ROWr16[2] (a1)
sub r3 , r6 , r11 @ R3=a0-W6*ROWr16[2] (a2)
mul r11 , r8 , r4 @ R11=W2*ROWr16[2]
sub r4 , r6 , r11 @ R4=a0-W2*ROWr16[2] (a3)
add r6 , r6 , r11 @ R6=a0+W2*ROWr16[2] (a0)
@@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3,
@@ R5=b2, R6=a0, R7=b3, R8=W2, R9=W4, R10=W6, R11 (free),
@@ R12=__const_ptr_, R14=&block[n]
@@ a0 += W4*row[4]
@@ a1 -= W4*row[4]
@@ a2 -= W4*row[4]
@@ a3 += W4*row[4]
ldrsh r11 , [ r14 , #64 ] @ R11=ROWr16[4]
teq r11 , #0 @ if null avoid muls
mulne r11 , r9 , r11 @ R11=W4*ROWr16[4]
@@ R9 is free now
addne r6 , r6 , r11 @ R6+=W4*ROWr16[4] (a0)
subne r2 , r2 , r11 @ R2-=W4*ROWr16[4] (a1)
subne r3 , r3 , r11 @ R3-=W4*ROWr16[4] (a2)
ldrsh r9 , [ r14 , #96 ] @ R9=ROWr16[6]
addne r4 , r4 , r11 @ R4+=W4*ROWr16[4] (a3)
@@ W6 alone is no more useful, save W2*ROWr16[6] in it instead
teq r9 , #0 @ if null avoid muls
mulne r11 , r10 , r9 @ R11=W6*ROWr16[6]
addne r6 , r6 , r11 @ R6+=W6*ROWr16[6] (a0)
mulne r10 , r8 , r9 @ R10=W2*ROWr16[6]
@@ a0 += W6*row[6];
@@ a3 -= W6*row[6];
@@ a1 -= W2*row[6];
@@ a2 += W2*row[6];
subne r4 , r4 , r11 @ R4-=W6*ROWr16[6] (a3)
subne r2 , r2 , r10 @ R2-=W2*ROWr16[6] (a1)
addne r3 , r3 , r10 @ R3+=W2*ROWr16[6] (a2)
__end_a_evaluation2 :
@@ at this point, R0=b0, R1=b1, R2=a1, R3=a2, R4=a3,
@@ R5=b2, R6=a0, R7=b3, R8 (free), R9 (free), R10 (free), R11 (free),
@@ R12=__const_ptr_, R14=&block[n]
@@ col[0 ] = ((a0 + b0) >> COL_SHIFT);
@@ col[8 ] = ((a1 + b1) >> COL_SHIFT);
@@ col[16] = ((a2 + b2) >> COL_SHIFT);
@@ col[24] = ((a3 + b3) >> COL_SHIFT);
@@ col[32] = ((a3 - b3) >> COL_SHIFT);
@@ col[40] = ((a2 - b2) >> COL_SHIFT);
@@ col[48] = ((a1 - b1) >> COL_SHIFT);
@@ col[56] = ((a0 - b0) >> COL_SHIFT);
@@@@@ no optimisation here @@@@@
add r8 , r6 , r0 @ R8=a0+b0
add r9 , r2 , r1 @ R9=a1+b1
mov r8 , r8 , a s r #C O L _ S H I F T
mov r9 , r9 , a s r #C O L _ S H I F T
strh r8 , [ r14 , #0 ]
strh r9 , [ r14 , #16 ]
add r8 , r3 , r5 @ R8=a2+b2
add r9 , r4 , r7 @ R9=a3+b3
mov r8 , r8 , a s r #C O L _ S H I F T
mov r9 , r9 , a s r #C O L _ S H I F T
strh r8 , [ r14 , #32 ]
strh r9 , [ r14 , #48 ]
sub r8 , r4 , r7 @ R8=a3-b3
sub r9 , r3 , r5 @ R9=a2-b2
mov r8 , r8 , a s r #C O L _ S H I F T
mov r9 , r9 , a s r #C O L _ S H I F T
strh r8 , [ r14 , #64 ]
strh r9 , [ r14 , #80 ]
sub r8 , r2 , r1 @ R8=a1-b1
sub r9 , r6 , r0 @ R9=a0-b0
mov r8 , r8 , a s r #C O L _ S H I F T
mov r9 , r9 , a s r #C O L _ S H I F T
strh r8 , [ r14 , #96 ]
strh r9 , [ r14 , #112 ]
__end_col_loop :
@@ at this point, R0-R11 (free)
@@ R12=__const_ptr_, R14=&block[n]
ldr r0 , [ s p , #0 ] @ R0=block
teq r0 , r14 @ compare current &block[n] to block, when block is reached, the loop is finished.
sub r14 , r14 , #2
bne _ _ c o l _ l o o p
__end_simple_idct_ARM :
@@ restore registers to previous status!
add s p , s p , #8 @@ the local variables!
ldmfd s p ! , { r4 - r11 , r15 } @@ update PC with LR content.
@@ kind of sub-function, here not to overload the common case.
__end_bef_a_evaluation :
add r2 , r6 , r11 @ R2=a0+W6*ROWr16[2] (a1)
mul r11 , r8 , r4 @ R11=W2*ROWr16[2]
sub r4 , r6 , r11 @ R4=a0-W2*ROWr16[2] (a3)
add r6 , r6 , r11 @ R6=a0+W2*ROWr16[2] (a0)
bal _ _ e n d _ a _ e v a l u a t i o n
__constant_ptr__ : @@ see #defines at the beginning of the source code for values.
.align
.word W1
.word W2
.word W3
.word W4
.word W5
.word W6
.word W7
.word MASK_MSHW
