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ASM optimization for fiq_playback(). Saves about 0.4MHz of CPU while playback on PP502x/PP5002.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17097 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andree Buschmann 2008-04-13 17:03:24 +00:00
parent 2bf4178018
commit b90a766d01
1 changed files with 61 additions and 23 deletions
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84
firmware/target/arm/pcm-pp.c
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@ -107,11 +107,17 @@ void pcm_apply_settings(void)
pcm_curr_sampr = pcm_freq; pcm_curr_sampr = pcm_freq;
} }
/* ASM optimised FIQ handler. GCC fails to make use of the fact that FIQ mode /* ASM optimised FIQ handler. Checks for the minimum allowed loop cycles by evalutation of
has registers r8-r14 banked, and so does not need to be saved. This routine * free IISFIFO-slots against available source buffer words. Through this it is possible to
uses only these registers, and so will never touch the stack unless it * move the check for IIS_TX_FREE_COUNT outside the loop and do some further optimization.
actually needs to do so when calling pcm_callback_for_more. C version is * Right after the loops (source buffer -> IISFIFO) are done we need to check whether we
still included below for reference and testing. * have to exit FIQ handler (this must be done, if all free FIFO slots were filled) or
* we will have to get some new source data.
* Important information kept from former ASM implementation (not used anymore): GCC fails
* to make use of the fact that FIQ mode has registers r8-r14 banked, and so does not need
* to be saved. This routine uses only these registers, and so will never touch the stack
* unless it actually needs to do so when calling pcm_callback_for_more. C version is still
* included below for reference and testing.
*/ */
#if 1 #if 1
void fiq_playback(void) ICODE_ATTR __attribute__((naked)); void fiq_playback(void) ICODE_ATTR __attribute__((naked));
@ -122,9 +128,11 @@ void fiq_playback(void)
* addresses we need are generated by using offsets with these two. * addresses we need are generated by using offsets with these two.
* r10 + 0x40 is IISFIFO_WR, and r10 + 0x0c is IISFIFO_CFG. * r10 + 0x40 is IISFIFO_WR, and r10 + 0x0c is IISFIFO_CFG.
* r8 and r9 contains local copies of p and size respectively. * r8 and r9 contains local copies of p and size respectively.
* r12 is a working register. * r0-r3 and r12 is a working register.
*/ */
asm volatile ( asm volatile (
"stmfd sp!, { r0-r3, lr } \n" /* stack scratch regs and lr */
#if CONFIG_CPU == PP5002 #if CONFIG_CPU == PP5002
"ldr r12, =0xcf001040 \n" /* Some magic from iPodLinux */ "ldr r12, =0xcf001040 \n" /* Some magic from iPodLinux */
"ldr r12, [r12] \n" "ldr r12, [r12] \n"
@ -132,24 +140,54 @@ void fiq_playback(void)
"ldmia r11, { r8-r9 } \n" /* r8 = p, r9 = size */ "ldmia r11, { r8-r9 } \n" /* r8 = p, r9 = size */
"cmp r9, #0 \n" /* is size 0? */ "cmp r9, #0 \n" /* is size 0? */
"beq .more_data \n" /* if so, ask pcmbuf for more data */ "beq .more_data \n" /* if so, ask pcmbuf for more data */
".fifo_loop: \n"
"ldr r12, [r10, %[cfg]] \n" /* read IISFIFO_CFG to check FIFO status */
"ands r12, r12, %[mask] \n"
"beq .exit \n" /* FIFO full, exit */
#if SAMPLE_SIZE == 16 #if SAMPLE_SIZE == 16
"ldr r12, [r8], #4 \n" /* load two samples */ ".check_fifo: \n"
"str r12, [r10, %[wr]] \n" /* write them */ "ldr r0, [r10, %[cfg]] \n" /* read IISFIFO_CFG to check FIFO status */
"and r0, r0, %[mask] \n" /* r0 = IIS_TX_FREE_COUNT << 16 (PP502x) */
"mov r1, r0, lsr #16 \n" /* number of free FIFO slots */
"cmp r1, r9, lsr #2 \n" /* number of words from source */
"movgt r1, r9, lsr #2 \n" /* r1 = amount of allowed loops */
"sub r9, r9, r1, lsl #2 \n" /* r1 words will be written in following loop */
"subs r1, r1, #2 \n"
".fifo_loop_2: \n"
"ldmgeia r8!, {r2, r12} \n" /* load four samples */
"strge r2 , [r10, %[wr]] \n" /* write sample 0-1 to IISFIFO_WR */
"strge r12, [r10, %[wr]] \n" /* write sample 2-3 to IISFIFO_WR */
"subges r1, r1, #2 \n" /* one more loop? */
"bge .fifo_loop_2 \n" /* yes, continue */
"tst r1, #1 \n" /* two samples (one word) left? */
"ldrne r12, [r8], #4 \n" /* load two samples */
"strne r12, [r10, %[wr]] \n" /* write sample 0-1 to IISFIFO_WR */
"cmp r9, #0 \n" /* either FIFO is full or source buffer is empty */
"bgt .exit \n" /* if source buffer is not empty, FIFO must be full */
#elif SAMPLE_SIZE == 32 #elif SAMPLE_SIZE == 32
".check_fifo: \n"
"ldr r0, [r10, %[cfg]] \n" /* read IISFIFO_CFG to check FIFO status */
"and r0, r0, %[mask] \n" /* r0 = IIS_TX_FREE_COUNT << 23 (PP5002) */
"mov r1, r0, lsr #24 \n" /* number of free pairs of FIFO slots */
"cmp r1, r9, lsr #2 \n" /* number of words from source */
"movgt r1, r9, lsr #2 \n" /* r1 = amount of allowed loops */
"sub r9, r9, r1, lsl #2 \n" /* r1 words will be written in following loop */
".fifo_loop: \n"
"ldr r12, [r8], #4 \n" /* load two samples */ "ldr r12, [r8], #4 \n" /* load two samples */
"mov r12, r12, ror #16 \n" /* put left sample at the top bits */ "mov r2 , r12, lsl #16 \n" /* put left sample at the top bits */
"str r12, [r10, %[wr]] \n" /* write top sample, lower sample ignored */ "str r2 , [r10, %[wr]] \n" /* write top sample to IISFIFO_WR */
"mov r12, r12, lsl #16 \n" /* shift lower sample up */ "str r12, [r10, %[wr]] \n" /* write low sample to IISFIFO_WR*/
"str r12, [r10, %[wr]] \n" /* then write it */ "subs r1, r1, #1 \n" /* one more loop? */
"bgt .fifo_loop \n" /* yes, continue */
"cmp r9, #0 \n" /* either FIFO is full or source buffer is empty */
"bgt .exit \n" /* if source buffer is not empty, FIFO must be full */
#endif #endif
"subs r9, r9, #4 \n" /* check if we have more samples */
"bne .fifo_loop \n" /* yes, continue */
".more_data: \n" ".more_data: \n"
"stmfd sp!, { r0-r3, lr } \n" /* stack scratch regs and lr */
"ldr r2, =pcm_callback_for_more \n" "ldr r2, =pcm_callback_for_more \n"
"ldr r2, [r2] \n" /* get callback address */ "ldr r2, [r2] \n" /* get callback address */
"cmp r2, #0 \n" /* check for null pointer */ "cmp r2, #0 \n" /* check for null pointer */
@ -160,21 +198,21 @@ void fiq_playback(void)
"bxne r2 \n" "bxne r2 \n"
"ldmia r11, { r8-r9 } \n" /* reload p and size */ "ldmia r11, { r8-r9 } \n" /* reload p and size */
"cmp r9, #0 \n" /* did we actually get more data? */ "cmp r9, #0 \n" /* did we actually get more data? */
"ldmnefd sp!, { r0-r3, lr } \n" "bne .check_fifo \n"
"bne .fifo_loop \n" /* yes, continue to try feeding FIFO */
"ldr r12, =pcm_play_dma_stop \n" "ldr r12, =pcm_play_dma_stop \n"
"mov lr, pc \n" "mov lr, pc \n"
"bx r12 \n" "bx r12 \n"
"ldr r12, =pcm_play_dma_stopped_callback \n" "ldr r12, =pcm_play_dma_stopped_callback \n"
"mov lr, pc \n" "mov lr, pc \n"
"bx r12 \n" "bx r12 \n"
"ldmfd sp!, { r0-r3, lr } \n"
".exit: \n" /* (r8=0 if stopping, look above) */ ".exit: \n" /* (r8=0 if stopping, look above) */
"stmia r11, { r8-r9 } \n" /* save p and size */ "stmia r11, { r8-r9 } \n" /* save p and size */
"ldmfd sp!, { r0-r3, lr } \n"
"subs pc, lr, #4 \n" /* FIQ specific return sequence */ "subs pc, lr, #4 \n" /* FIQ specific return sequence */
".ltorg \n" ".ltorg \n"
: /* These must only be integers! No regs */ : /* These must only be integers! No regs */
: [mask]"i"(IIS_TX_FREE_MASK & (IIS_TX_FREE_MASK-1)), : [mask]"i"(IIS_TX_FREE_MASK),
[cfg]"i"((int)&IISFIFO_CFG - (int)&IISCONFIG), [cfg]"i"((int)&IISFIFO_CFG - (int)&IISCONFIG),
[wr]"i"((int)&IISFIFO_WR - (int)&IISCONFIG) [wr]"i"((int)&IISFIFO_WR - (int)&IISCONFIG)
); );