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bzip2: eliminate some divisions

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This commit is contained in:
Denis Vlasenko
2007-10-14 07:49:48 +00:00
parent 3f5fdc7572
commit 6a9154b6f6
3 changed files with 51 additions and 35 deletions
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20
archival/bz/compress.c
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@@ -186,7 +186,8 @@ void generateMTFValues(EState* s)
s->mtfFreq[BZ_RUNA]++;
}
if (zPend < 2) break;
zPend = (zPend - 2) / 2;
zPend = (uint32_t)(zPend - 2) / 2;
/* bbox: unsigned div is easier */
};
zPend = 0;
}
@@ -219,15 +220,18 @@ void generateMTFValues(EState* s)
zPend--;
while (1) {
if (zPend & 1) {
mtfv[wr] = BZ_RUNB; wr++;
mtfv[wr] = BZ_RUNB;
wr++;
s->mtfFreq[BZ_RUNB]++;
} else {
mtfv[wr] = BZ_RUNA; wr++;
mtfv[wr] = BZ_RUNA;
wr++;
s->mtfFreq[BZ_RUNA]++;
}
if (zPend < 2)
break;
zPend = (zPend - 2) / 2;
zPend = (uint32_t)(zPend - 2) / 2;
/* bbox: unsigned div is easier */
};
zPend = 0;
}
@@ -288,7 +292,7 @@ void sendMTFValues(EState* s)
gs = 0;
while (nPart > 0) {
tFreq = remF / nPart;
ge = gs-1;
ge = gs - 1;
aFreq = 0;
while (aFreq < tFreq && ge < alphaSize-1) {
ge++;
@@ -297,7 +301,7 @@ void sendMTFValues(EState* s)
if (ge > gs
&& nPart != nGroups && nPart != 1
&& ((nGroups - nPart) % 2 == 1)
&& ((nGroups - nPart) % 2 == 1) /* bbox: can this be replaced by x & 1? */
) {
aFreq -= s->mtfFreq[ge];
ge--;
@@ -310,7 +314,7 @@ void sendMTFValues(EState* s)
s->len[nPart-1][v] = BZ_GREATER_ICOST;
nPart--;
gs = ge+1;
gs = ge + 1;
remF -= aFreq;
}
}
@@ -414,7 +418,7 @@ void sendMTFValues(EState* s)
/*
* Increment the symbol frequencies for the selected table.
*/
/* 1% faster compress. +800 bytes */
/* 1% faster compress. +800 bytes */
#if CONFIG_BZIP2_FEATURE_SPEED >= 4
if (nGroups == 6 && 50 == ge-gs+1) {
/*--- fast track the common case ---*/