Use the __builtin_clzll() function of gcc to improve the performance and

reduce the size of the sqlite3LogEst() routine.

FossilOrigin-Name: a42a438cbbd721765ca55e71c464552dbaa494050cf472593599b8c7f0249516

diff --git a/manifest b/manifest
index 92d8e3f2823a63cff0148b8b36eb180342e87ef4..bb8ae26a385d7dd24f80cb9ec0e97f987ab1732a 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Small\soptimization\sin\sthe\sExpr\stree\swalker.
-D 2017-08-17T19:23:16.310
+C Use\sthe\s__builtin_clzll()\sfunction\sof\sgcc\sto\simprove\sthe\sperformance\sand\nreduce\sthe\ssize\sof\sthe\ssqlite3LogEst()\sroutine.
+D 2017-08-17T20:53:07.912
 F Makefile.in d9873c9925917cca9990ee24be17eb9613a668012c85a343aef7e5536ae266e8
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 02b469e9dcd5b7ee63fc1fb05babc174260ee4cfa4e0ef2e48c3c6801567a016
@@ -522,7 +522,7 @@ F src/treeview.c 2ee4a5dada213d5ab08a742af5c876cee6f1aaae65f10a61923f3fb63846afe
 F src/trigger.c 48e0f7ed6749ce4d50a695e09e20ce9cf84ecabf2691852c965a51e0b620eccc
 F src/update.c 5404be9e840717323a69209190cdbc9d0d34adaedaaf1d1a1069babf2c4171c0
 F src/utf.c 810fbfebe12359f10bc2a011520a6e10879ab2a163bcb26c74768eab82ea62a5
-F src/util.c fc081ec6f63448dcd80d3dfad35baecfa104823254a815b081a4d9fe76e1db23
+F src/util.c 773843506ce694714bc96fe67c30c37015f90ef515d0e70f1f8d5c9c24088152
 F src/vacuum.c 90839322fd5f00df9617eb21b68beda9b6e2a2937576b0d65985e4aeb1c53739
 F src/vdbe.c 711a1b2c0a6046483ebf4ac43c4c0ea5bef3e50534a4ab9e1d7e3542635cd009
 F src/vdbe.h d50cadf12bcf9fb99117ef392ce1ea283aa429270481426b6e8b0280c101fd97
@@ -1649,7 +1649,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 0367a4d58682a64d7ed4c5a4b4377899e22432851587c649d419efb6d7bac250
-R ff1cbce154569f3d7cb9695eac015fa5
+P 264a5e1b75ee073bd019483e289c3d8d79abcf5a765435be23ac3c21b1db8246
+R 08353d9c0ca9dacc46ddab1c0e437979
 U drh
-Z 24e86d635456e5a8dccd5aa790210fdc
+Z 35417eeee14d21861c3f9ed9415c7596

diff --git a/manifest.uuid b/manifest.uuid
index fb45173c1a2bab6777e812a5fc73f20d63e7dd22..04447e26d5b5787e08ee628c45e5bcd96a8614d8 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-264a5e1b75ee073bd019483e289c3d8d79abcf5a765435be23ac3c21b1db8246
\ No newline at end of file
+a42a438cbbd721765ca55e71c464552dbaa494050cf472593599b8c7f0249516
\ No newline at end of file

diff --git a/src/util.c b/src/util.c
index 7c9c5f54b75e9146a29121c70596dc058b4207d9..a6d349296f6259eac6933c11a6ad4ea8a285f032 100644 (file)
--- a/src/util.c
+++ b/src/util.c
@@ -1413,8 +1413,14 @@ LogEst sqlite3LogEst(u64 x){
     if( x<2 ) return 0;
     while( x<8 ){  y -= 10; x <<= 1; }
   }else{
+#if GCC_VERSION>=5004000
+    int i = 60 - __builtin_clzll(x);
+    y += i*10;
+    x >>= i;
+#else
     while( x>255 ){ y += 40; x >>= 4; }  /*OPTIMIZATION-IF-TRUE*/
     while( x>15 ){  y += 10; x >>= 1; }
+#endif
   }
   return a[x&7] + y - 10;
 }