From: drh <drh@noemail.net>
Date: Mon, 25 Jan 2016 15:57:29 +0000 (+0000)
Subject: Replace the OP_SetIfNotPos operator with OP_OffsetLimit in the VDBE, for
X-Git-Tag: version-3.11.0~94
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=cc2fa4cf5599637bdb8f5a2cc64f0805243e04e4;p=thirdparty%2Fsqlite.git

Replace the OP_SetIfNotPos operator with OP_OffsetLimit in the VDBE, for
simpler and smaller code.

FossilOrigin-Name: 7ac017a498b6fb28343eef2d24e400c7800660d6
---

diff --git a/manifest b/manifest
index 69e58459fa..827a3d5126 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sthe\sSQLITE_EXTRA_DURABLE\scompile-time\soption.
-D 2016-01-25T13:55:47.049
+C Replace\sthe\sOP_SetIfNotPos\soperator\swith\sOP_OffsetLimit\sin\sthe\sVDBE,\sfor\nsimpler\sand\ssmaller\scode.
+D 2016-01-25T15:57:29.060
 F Makefile.in 027c1603f255390c43a426671055a31c0a65fdb4
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 1708a78eda223b6daa302b140037fcc214a779f9
@@ -345,7 +345,7 @@ F src/printf.c af589a27b7d40f6f4f704e9eea99f02f18ad6d32
 F src/random.c ba2679f80ec82c4190062d756f22d0c358180696
 F src/resolve.c 9f7ce3a3c087afb7597b7c916c99126ff3f12f0c
 F src/rowset.c eccf6af6d620aaa4579bd3b72c1b6395d9e9fa1e
-F src/select.c 1db9a902e89201a0ae3ff5243a7a3f37842a3937
+F src/select.c c34292c8ce7fe69c7cf890d933834a22572bd301
 F src/shell.c dcd7a83645ef2a58ee9c6d0ea4714d877d7835c4
 F src/sqlite.h.in 214476a62012e578f42133a9a3b4f97a9aa421a3
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -410,7 +410,7 @@ F src/update.c 17332f9fe818cbc0444c36a811800af8498af4c3
 F src/utf.c 32d7f82aa921322f3e1c956f4b58f019ebd2c6b3
 F src/util.c 72d40df0a52d3f30b462a15f0e094fcbade6dc82
 F src/vacuum.c 2ddd5cad2a7b9cef7f9e431b8c7771634c6b1701
-F src/vdbe.c b90d9d38e5e0260c2eafa3cb4c2274d8ea94da27
+F src/vdbe.c 3ffbcc413bf793e3f0b95b79ef2f4bd449a5b5a3
 F src/vdbe.h 7a733ea8aac1b77305a67698e784fa3484ee3337
 F src/vdbeInt.h 42eefa4f9e7432b9968d321b44e48821ec13b189
 F src/vdbeapi.c ffae8f5af4570fbd548504e815e9fb7227f0822e
@@ -1419,7 +1419,7 @@ F tool/vdbe_profile.tcl 246d0da094856d72d2c12efec03250d71639d19f
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 8a1deae497edf3fa43fa96152d140405398c5ed6
-R ae4ccddaf3c593cdf1ed2beb484cfd15
+P 30671345b1c1ee55a2d1aa17273213f1849efd81
+R f342889ba3409bd63b1cf54d88bfe0e2
 U drh
-Z 297086babbdf85e61ae58e42a437c1ec
+Z e7c5fc86067d4269675714897cec0b51
diff --git a/manifest.uuid b/manifest.uuid
index 439be2e5fa..276ef7a03f 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-30671345b1c1ee55a2d1aa17273213f1849efd81
\ No newline at end of file
+7ac017a498b6fb28343eef2d24e400c7800660d6
\ No newline at end of file
diff --git a/src/select.c b/src/select.c
index ffc0ec2415..ea4298e677 100644
--- a/src/select.c
+++ b/src/select.c
@@ -1860,10 +1860,8 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
       sqlite3ExprCode(pParse, p->pOffset, iOffset);
       sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset); VdbeCoverage(v);
       VdbeComment((v, "OFFSET counter"));
-      sqlite3VdbeAddOp3(v, OP_SetIfNotPos, iOffset, iOffset, 0);
-      sqlite3VdbeAddOp3(v, OP_Add, iLimit, iOffset, iOffset+1);
+      sqlite3VdbeAddOp3(v, OP_OffsetLimit, iLimit, iOffset+1, iOffset);
       VdbeComment((v, "LIMIT+OFFSET"));
-      sqlite3VdbeAddOp3(v, OP_SetIfNotPos, iLimit, iOffset+1, -1);
     }
   }
 }
@@ -2280,9 +2278,8 @@ static int multiSelect(
         addr = sqlite3VdbeAddOp1(v, OP_IfNot, p->iLimit); VdbeCoverage(v);
         VdbeComment((v, "Jump ahead if LIMIT reached"));
         if( p->iOffset ){
-          sqlite3VdbeAddOp3(v, OP_SetIfNotPos, p->iOffset, p->iOffset, 0);
-          sqlite3VdbeAddOp3(v, OP_Add, p->iLimit, p->iOffset, p->iOffset+1);
-          sqlite3VdbeAddOp3(v, OP_SetIfNotPos, p->iLimit, p->iOffset+1, -1);
+          sqlite3VdbeAddOp3(v, OP_OffsetLimit,
+                            p->iLimit, p->iOffset+1, p->iOffset);
         }
       }
       explainSetInteger(iSub2, pParse->iNextSelectId);
diff --git a/src/vdbe.c b/src/vdbe.c
index c6d5f7b0cc..cfff895c30 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -5757,20 +5757,31 @@ case OP_IfPos: {        /* jump, in1 */
   break;
 }
 
-/* Opcode: SetIfNotPos P1 P2 P3 * *
-** Synopsis: if r[P1]<=0 then r[P2]=P3
+/* Opcode: OffsetLimit P1 P2 P3 * *
+** Synopsis: if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1)
 **
-** Register P1 must contain an integer.
-** If the value of register P1 is not positive (if it is less than 1) then
-** set the value of register P2 to be the integer P3.
+** This opcode performs a commonly used computation associated with
+** LIMIT and OFFSET process.  r[P1] holds the limit counter.  r[P3]
+** holds the offset counter.  The opcode computes the combined value
+** of the LIMIT and OFFSET and stores that value in r[P2].  The r[P2]
+** value computed is the total number of rows that will need to be
+** visited in order to complete the query.
+**
+** If r[P3] is zero or negative, that means there is no OFFSET
+** and r[P2] is set to be the value of the LIMIT, r[P1].
+**
+** if r[P1] is zero or negative, that means there is no LIMIT
+** and r[P2] is set to -1. 
+**
+** Otherwise, r[P2] is set to the sum of r[P1] and r[P3].
 */
-case OP_SetIfNotPos: {        /* in1, in2 */
+case OP_OffsetLimit: {    /* in1, out2, in3 */
   pIn1 = &aMem[pOp->p1];
-  assert( pIn1->flags&MEM_Int );
-  if( pIn1->u.i<=0 ){
-    pOut = out2Prerelease(p, pOp);
-    pOut->u.i = pOp->p3;
-  }
+  pIn3 = &aMem[pOp->p3];
+  pOut = out2Prerelease(p, pOp);
+  assert( pIn1->flags & MEM_Int );
+  assert( pIn3->flags & MEM_Int );
+  pOut->u.i = pIn1->u.i<=0 ? -1 : pIn1->u.i+(pIn3->u.i>0?pIn3->u.i:0);
   break;
 }