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opus: hold cwrsi's row pair, and test it with one comparison

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53% of the dimensions a decode walks hold no pulses, and that arm leaves
_k alone, so the two CELT_PVQ_U_ROW pointers stay valid.  U is
non-decreasing in _k, so p <= _i < q is the single unsigned test
(_i-p) < (q-p).  Bit-exact over 8.2M samples.

Modelled: -0.40% ARMv4, -0.78% ARMv5E; the function -4.8% and -7.1%.
Measured: e200v1 39.19 -> 38.96 MHz, Clip+ 28.13 -> 28.08 MHz.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Change-Id: Id50be222e101aeabd9a1f4cf5380d3244da610ff
This commit is contained in:
Michael Giacomelli 2026-09-18 11:59:30 -04:00
parent 93d564426b
commit 5a6935047e
1 changed files with 34 additions and 6 deletions
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40
lib/rbcodec/codecs/libopus/celt/cwrs.c
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@ -461,13 +461,21 @@ void encode_pulses(const int *_y,int _n,int _k,ec_enc *_enc){
}
static opus_val32 cwrsi(int _n,int _k,opus_uint32 _i,int *_y){
const opus_uint32 *rk;
const opus_uint32 *rk1;
opus_uint32 p;
opus_uint32 d;
int s;
int k0;
int kc;
opus_int16 val;
opus_val32 yy=0;
celt_assert(_k>0);
celt_assert(_n>1);
/*_k never goes negative, so this cannot match before the pair has been
loaded once.*/
kc=-1;
rk=rk1=NULL;
while(_n>2){
opus_uint32 q;
/*Lots of pulses case:*/
@ -495,12 +503,32 @@ static opus_val32 cwrsi(int _n,int _k,opus_uint32 _i,int *_y){
}
/*Lots of dimensions case:*/
else{
/*Are there any pulses in this dimension at all?*/
p=CELT_PVQ_U_ROW[_k][_n];
q=CELT_PVQ_U_ROW[_k+1][_n];
if(p<=_i&&_i<q){
_i-=p;
*_y++=0;
if(_k!=kc){
rk=CELT_PVQ_U_ROW[_k];
rk1=CELT_PVQ_U_ROW[_k+1];
kc=_k;
}
p=rk[_n];
q=rk1[_n];
celt_sig_assert(p<=q);
d=_i-p;
if(d<q-p){
/*None, and more than half of all dimensions end here. The next
dimension reads the same two rows one element lower, so test it
from inside this loop instead of going back through the dispatch
above, which would reload both row pointers to reach it.*/
for(;;){
_i=d;
*_y++=0;
_n--;
if(_n<=2||_k>=_n)break;
p=rk[_n];
q=rk1[_n];
d=_i-p;
if(d>=q-p)break;
}
/*_n is already decremented for every dimension handled above.*/
continue;
}
else{
/*Are the pulses in this dimension negative?*/