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Optimize overlap_math by only doing shifting if theres gain, and moving the check for sign outside of the for loop. 3% speedup on PP5024.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21940 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Michael Giacomelli 2009-07-18 00:24:54 +00:00
parent b957f7214b
commit 6539b535ad
1 changed files with 14 additions and 3 deletions
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17
apps/codecs/libcook/cook_fixpoint.h
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@ -268,9 +268,20 @@ static inline void imlt_math(COOKContext *q, FIXP *in)
static inline void overlap_math(COOKContext *q, int gain, FIXP buffer[])
{
int i;
for(i=0 ; i<q->samples_per_channel ; i++) {
q->mono_mdct_output[i] =
fixp_pow2(q->mono_mdct_output[i], gain) + buffer[i];
if(LIKELY(gain == 0)){
for(i=0 ; i<q->samples_per_channel ; i++) {
q->mono_mdct_output[i] += buffer[i];
}
} else if (gain > 0){
for(i=0 ; i<q->samples_per_channel ; i++) {
q->mono_mdct_output[i] = (q->mono_mdct_output[i]<< gain) + buffer[i]; }
} else {
for(i=0 ; i<q->samples_per_channel ; i++) {
q->mono_mdct_output[i] =
(q->mono_mdct_output[i] >> -gain) + ((q->mono_mdct_output[i] >> (-gain-1)) & 1)+ buffer[i];
}
}
}