bzip2: eliminate some divisions

3 files changed, 51 insertions, 35 deletions

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;
                 }