Improved rounding even on systems with an 8-byte "long double" type.

FossilOrigin-Name: 15202aee150fa8e15fb90e90e5765c5e19a1eaf4896da2996a747636b76da8e6

manifest

@@ -1,5 +1,5 @@
-C Performance\senhancement\sin\ssqlite3AtoF().\s\sAbout\s8%\sfaster.
-D 2019-05-25T18:17:53.260
+C Improved\srounding\seven\son\ssystems\swith\san\s8-byte\s"long\sdouble"\stype.
+D 2019-05-27T00:29:15.840
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -518,7 +518,7 @@ F src/pcache1.c be64b2f3908a7f97c56c963676eb12f0d6254c95b28cdc1d73a186eff213219d
 F src/pragma.c 925bcac0afd98a0d4255c7524b93239ab4d83893d96f7f8fdccd78d4929a39bb
 F src/pragma.h 4a9fabff14db4487a734dfeeb4be984ce662bfdccfae16145b9c732327735e13
 F src/prepare.c 78027c6231fbb19ca186a5f5f0c0a1375d9c2cec0655273f9bd90d9ff74a34b3
-F src/printf.c 23a0fd3c81637d3d05340919d8a65963091e5f6597db1d275cdc9742dd970165
+F src/printf.c 9be6945837c839ba57837b4bc3af349eba630920fa5532aa518816defe42a7d4
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c bae0a7562db77b02d87101b587819d5a5dcd8625e477d2d8a228a20bba4fead6
 F src/rowset.c d977b011993aaea002cab3e0bb2ce50cf346000dff94e944d547b989f4b1fe93
@@ -1244,7 +1244,7 @@ F test/resolver01.test f4022acafda7f4d40eca94dbf16bc5fc4ac30ceb
 F test/rollback.test 06680159bc6746d0f26276e339e3ae2f951c64812468308838e0a3362d911eaa
 F test/rollback2.test bc868d57899dc6972e2b4483faae0e03365a0556941474eec487ae21d8d38bb6
 F test/rollbackfault.test 0e646aeab8840c399cfbfa43daab46fd609cf04a
-F test/round1.test 138fc19eb8798fac8a475e3c624b8d7736ea12b65ecef43bb6bcf071b3c63a81
+F test/round1.test 768018b04522ca420b1aba8a24bd76091d269f3bce3902af3ec6ebcee41ab21e
 F test/rowallock.test 3f88ec6819489d0b2341c7a7528ae17c053ab7cc
 F test/rowhash.test 0bc1d31415e4575d10cacf31e1a66b5cc0f8be81
 F test/rowid.test bfbd7b97d9267660be3c8f28507c4ed7f205196b8877c0db42df347c2e8845e3
@@ -1829,7 +1829,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 2e2ebad3ab636c4c65814ad41d417b105be8e254d609d0e08fbba4c5bd107bf3
-R ef9208359f9605c768184cd8045692e9
+P 81721aa54587e20d031d528fb6b74d91671a6e950fa926dc63f4284466e70f0e
+R c9de0c36c0333668e5f2f8e4d611250f
 U drh
-Z f6f659f82b7441453c2104f0c0b3b1fb
+Z 1cb14885af88ddd3e3ec785d1bef950d

manifest.uuid

@@ -1 +1 @@
-81721aa54587e20d031d528fb6b74d91671a6e950fa926dc63f4284466e70f0e
+15202aee150fa8e15fb90e90e5765c5e19a1eaf4896da2996a747636b76da8e6

src/printf.c

@@ -527,7 +527,12 @@ void sqlite3_str_vappendf(
         rounder = arRound[idx%10];
         while( idx>=10 ){ rounder *= 1.0e-10; idx -= 10; }
         if( xtype==etFLOAT ){
-          if( precision<17) rounder += realvalue*2.0e-16;
+          double rx = (double)realvalue;
+          sqlite3_uint64 u;
+          int ex;
+          memcpy(&u, &rx, sizeof(u));
+          ex = -1023 + (int)((u>>52)&0x7ff);
+          if( precision+(ex/3) < 15 ) rounder += realvalue*3e-16;
           realvalue += rounder;
         }
         /* Normalize realvalue to within 10.0 > realvalue >= 1.0 */

test/round1.test

@@ -15,14 +15,9 @@ set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 set testprefix round1
 
-if {$::longdouble_size<=8} {
-  finish_test
-  return
-}
-
 expr srand(0)
 unset -nocomplain iTest
-for {set iTest 1} {$iTest<=10000} {incr iTest} {
+for {set iTest 1} {$iTest<=50000} {incr iTest} {
    set x1 [expr int(rand()*100000)]
    set x2 [expr int(rand()*100000)+1000*int(rand()*10000)]
    set n [expr int(rand()*8)+1]