Performance improvements in btreeParseCell() by inlining the varint decoder.

FossilOrigin-Name: faab0ed928074f3ec7c25e1a2058414fbd9b013c

manifest

@@ -1,5 +1,5 @@
-C Add\sthe\sMemPage.xParseCell\smethod\sand\sprovide\svarious\simplementations\n(variations\son\sthe\sformer\sbtreeParseCellPtr())\sdepending\son\sthe\spage\stype.
-D 2015-06-19T17:19:34.228
+C Performance\simprovements\sin\sbtreeParseCell()\sby\sinlining\sthe\svarint\sdecoder.
+D 2015-06-19T18:24:37.928
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 1063c58075b7400d93326b0eb332b48a54f53025
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -192,7 +192,7 @@ F src/auth.c b56c78ebe40a2110fd361379f7e8162d23f92240
 F src/backup.c ff743689c4d6c5cb55ad42ed9d174b2b3e71f1e3
 F src/bitvec.c 5eb7958c3bf65210211cbcfc44eff86d0ded7c9d
 F src/btmutex.c 45a968cc85afed9b5e6cf55bf1f42f8d18107f79
-F src/btree.c cf8310b4429e5f0400868b598d75d414b32da98e
+F src/btree.c 32d2d8674e462ed7f9343a83a304c5651165f539
 F src/btree.h 969adc948e89e449220ff0ff724c94bb2a52e9f1
 F src/btreeInt.h 6ece2dd9c8e2eac05f0a8ded8772a44e96486c65
 F src/build.c b3f15255d5b16e42dafeaa638fd4f8a47c94ed70
@@ -1286,7 +1286,10 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 02f7e9d7d7b93d0b6bbd6cc0d0359b3b741b9931
-R 2f4b41ef502fc9cfa753afb16ada8794
+P 41d03d883c4f7ca279eb9dd679f3ab81c8d957d9
+R 7c0a97271e0bde50dd22074cdc063563
+T *branch * btree-opt
+T *sym-btree-opt *
+T -sym-trunk *
 U drh
-Z a171034151748a0b17304cc3b38b62ab
+Z 88046b08ce75f4bf4926f31a639805e5

manifest.uuid

@@ -1 +1 @@
-41d03d883c4f7ca279eb9dd679f3ab81c8d957d9
+faab0ed928074f3ec7c25e1a2058414fbd9b013c

src/btree.c

@@ -1054,6 +1054,7 @@ static void btreeParseCellPtr(
 ){
   u8 *pIter;              /* For scanning through pCell */
   u32 nPayload;           /* Number of bytes of cell payload */
+  u64 iKey;               /* Extracted Key value */
 
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
   assert( pPage->leaf==0 || pPage->leaf==1 );
@@ -1061,8 +1062,46 @@ static void btreeParseCellPtr(
   assert( pPage->noPayload==0 );
   assert( pPage->intKeyLeaf );
   assert( pPage->childPtrSize==0 );
-  pIter = pCell + getVarint32(pCell, nPayload);
-  pIter += getVarint(pIter, (u64*)&pInfo->nKey);
+  pIter = pCell;
+
+  /* The next block of code is equivalent to:
+  **
+  **     pIter += getVarint32(pIter, nPayload);
+  **
+  ** The code is inlined to avoid a function call.
+  */
+  nPayload = *pIter;
+  if( nPayload>=0x80 ){
+    u8 *pEnd = &pIter[9];
+    nPayload &= 0x7f;
+    do{
+      nPayload = (nPayload<<7) | (*++pIter & 0x7f);
+    }while( (*pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+
+  /* The next block of code is equivalent to:
+  **
+  **     pIter += getVarint(pIter, (u64*)&pInfo->nKey);
+  **
+  ** The code is inlined to avoid a function call.
+  */
+  iKey = *pIter;
+  if( iKey>=0x80 ){
+    u8 *pEnd = &pIter[7];
+    iKey &= 0x7f;
+    while(1){
+      iKey = (iKey<<7) | (*++pIter & 0x7f);
+      if( (*pIter)<0x80 ) break;
+      if( pIter>=pEnd ){
+        iKey = (iKey<<8) | *++pIter;
+        break;
+      }
+    }
+  }
+  pIter++;
+
+  pInfo->nKey = *(i64*)&iKey;
   pInfo->nPayload = nPayload;
   pInfo->pPayload = pIter;
   testcase( nPayload==pPage->maxLocal );