From: Denis Vlasenko <vda.linux@googlemail.com>
Date: Sun, 14 Oct 2007 07:49:48 +0000 (-0000)
Subject: bzip2: eliminate some divisions
X-Git-Tag: 1_8_0~50
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=6a9154b6f649341870bc06e896d2fe7235a4aef9;p=oweals%2Fbusybox.git
bzip2: eliminate some divisions
---
diff --git a/archival/bz/blocksort.c b/archival/bz/blocksort.c
index ec8a2a56b..aaed883de 100644
--- a/archival/bz/blocksort.c
+++ b/archival/bz/blocksort.c
@@ -246,7 +246,12 @@ void fallbackSort(uint32_t* fmap,
for (i = 0; i < 257; i++) ftab[i] = 0;
for (i = 0; i < nblock; i++) ftab[eclass8[i]]++;
for (i = 0; i < 256; i++) ftabCopy[i] = ftab[i];
- for (i = 1; i < 257; i++) ftab[i] += ftab[i-1];
+
+ j = ftab[0]; /* bbox: optimized */
+ for (i = 1; i < 257; i++) {
+ j += ftab[i];
+ ftab[i] = j;
+ }
for (i = 0; i < nblock; i++) {
j = eclass8[i];
@@ -255,7 +260,7 @@ void fallbackSort(uint32_t* fmap,
fmap[k] = i;
}
- nBhtab = 2 + (nblock / 32);
+ nBhtab = 2 + ((uint32_t)nblock / 32); /* bbox: unsigned div is easier */
for (i = 0; i < nBhtab; i++) bhtab[i] = 0;
for (i = 0; i < 256; i++) SET_BH(ftab[i]);
@@ -737,27 +742,27 @@ void mainSort(uint32_t* ptr,
memset(ftab, 0, 65537 * sizeof(ftab[0]));
j = block[0] << 8;
- i = nblock-1;
+ i = nblock - 1;
/* 3%, +300 bytes */
#if CONFIG_BZIP2_FEATURE_SPEED >= 2
for (; i >= 3; i -= 4) {
quadrant[i] = 0;
- j = (j >> 8) |(((uint16_t)block[i]) << 8);
+ j = (j >> 8) | (((uint16_t)block[i]) << 8);
ftab[j]++;
quadrant[i-1] = 0;
- j = (j >> 8) |(((uint16_t)block[i-1]) << 8);
+ j = (j >> 8) | (((uint16_t)block[i-1]) << 8);
ftab[j]++;
quadrant[i-2] = 0;
- j = (j >> 8) |(((uint16_t)block[i-2]) << 8);
+ j = (j >> 8) | (((uint16_t)block[i-2]) << 8);
ftab[j]++;
quadrant[i-3] = 0;
- j = (j >> 8) |(((uint16_t)block[i-3]) << 8);
+ j = (j >> 8) | (((uint16_t)block[i-3]) << 8);
ftab[j]++;
}
#endif
for (; i >= 0; i--) {
quadrant[i] = 0;
- j = (j >> 8) |(((uint16_t)block[i]) << 8);
+ j = (j >> 8) | (((uint16_t)block[i]) << 8);
ftab[j]++;
}
@@ -768,34 +773,37 @@ void mainSort(uint32_t* ptr,
}
/*-- Complete the initial radix sort --*/
- for (i = 1; i <= 65536; i++)
- ftab[i] += ftab[i-1];
+ j = ftab[0]; /* bbox: optimized */
+ for (i = 1; i <= 65536; i++) {
+ j += ftab[i];
+ ftab[i] = j;
+ }
s = block[0] << 8;
- i = nblock-1;
+ i = nblock - 1;
#if CONFIG_BZIP2_FEATURE_SPEED >= 2
for (; i >= 3; i -= 4) {
s = (s >> 8) | (block[i] << 8);
- j = ftab[s] -1;
+ j = ftab[s] - 1;
ftab[s] = j;
ptr[j] = i;
s = (s >> 8) | (block[i-1] << 8);
- j = ftab[s] -1;
+ j = ftab[s] - 1;
ftab[s] = j;
ptr[j] = i-1;
s = (s >> 8) | (block[i-2] << 8);
- j = ftab[s] -1;
+ j = ftab[s] - 1;
ftab[s] = j;
ptr[j] = i-2;
s = (s >> 8) | (block[i-3] << 8);
- j = ftab[s] -1;
+ j = ftab[s] - 1;
ftab[s] = j;
ptr[j] = i-3;
}
#endif
for (; i >= 0; i--) {
s = (s >> 8) | (block[i] << 8);
- j = ftab[s] -1;
+ j = ftab[s] - 1;
ftab[s] = j;
ptr[j] = i;
}
@@ -812,21 +820,23 @@ void mainSort(uint32_t* ptr,
{
int32_t vv;
- /* was: int32_t h = 1; */
+ /* bbox: was: int32_t h = 1; */
/* do h = 3 * h + 1; while (h <= 256); */
- int32_t h = 364;
+ uint32_t h = 364;
do {
- h = h / 3;
+ /*h = h / 3;*/
+ h = (h * 171) >> 9; /* bbox: fast h/3 */
for (i = h; i <= 255; i++) {
vv = runningOrder[i];
j = i;
while (BIGFREQ(runningOrder[j-h]) > BIGFREQ(vv)) {
runningOrder[j] = runningOrder[j-h];
j = j - h;
- if (j <= (h - 1)) goto zero;
+ if (j <= (h - 1))
+ goto zero;
}
- zero:
+ zero:
runningOrder[j] = vv;
}
} while (h != 1);
@@ -860,10 +870,10 @@ void mainSort(uint32_t* ptr,
if (j != ss) {
sb = (ss << 8) + j;
if (!(ftab[sb] & SETMASK)) {
- int32_t lo = ftab[sb] & CLEARMASK;
+ int32_t lo = ftab[sb] & CLEARMASK;
int32_t hi = (ftab[sb+1] & CLEARMASK) - 1;
if (hi > lo) {
- mainQSort3 (
+ mainQSort3(
ptr, block, quadrant, nblock,
lo, hi, BZ_N_RADIX, budget
);
@@ -966,15 +976,14 @@ void mainSort(uint32_t* ptr,
while ((bbSize >> shifts) > 65534) shifts++;
for (j = bbSize-1; j >= 0; j--) {
- int32_t a2update = ptr[bbStart + j];
- uint16_t qVal = (uint16_t)(j >> shifts);
+ int32_t a2update = ptr[bbStart + j];
+ uint16_t qVal = (uint16_t)(j >> shifts);
quadrant[a2update] = qVal;
if (a2update < BZ_N_OVERSHOOT)
quadrant[a2update + nblock] = qVal;
}
AssertH(((bbSize-1) >> shifts) <= 65535, 1002);
}
-
}
}
@@ -1041,7 +1050,8 @@ void BZ2_blockSort(EState* s)
s->origPtr = -1;
for (i = 0; i < s->nblock; i++)
if (ptr[i] == 0) {
- s->origPtr = i; break;
+ s->origPtr = i;
+ break;
};
AssertH(s->origPtr != -1, 1003);
diff --git a/archival/bz/compress.c b/archival/bz/compress.c
index 3e2fbd867..724474e2d 100644
--- a/archival/bz/compress.c
+++ b/archival/bz/compress.c
@@ -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 ---*/
diff --git a/archival/bz/huffman.c b/archival/bz/huffman.c
index 3f80c9976..02838c496 100644
--- a/archival/bz/huffman.c
+++ b/archival/bz/huffman.c
@@ -183,6 +183,8 @@ void BZ2_hbMakeCodeLengths(uint8_t *len,
for (i = 1; i <= alphaSize; i++) {
j = weight[i] >> 8;
+ /* bbox: yes, it is a signed division.
+ * don't replace with shift! */
j = 1 + (j / 2);
weight[i] = j << 8;
}