Add a count parameter to the OP_Variable opcode and use it to simplify

prepared statements that copy consecutive unnamed parameters into
consecutive registers (a common case). (CVS 6309)

FossilOrigin-Name: 48b77b04935d8942eb22f0c061f3bc5e99bbd7db

1 files changed, 21 insertions, 4 deletions

diff --git a/src/expr.c b/src/expr.c
index ef7c54d28..8bc85fcb5 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -12,7 +12,7 @@
 ** This file contains routines used for analyzing expressions and
 ** for generating VDBE code that evaluates expressions in SQLite.
 **
-** $Id: expr.c,v 1.412 2009/02/19 14:39:25 danielk1977 Exp $
+** $Id: expr.c,v 1.413 2009/02/20 03:55:05 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -2002,9 +2002,26 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
     }
 #endif
     case TK_VARIABLE: {
-      sqlite3VdbeAddOp2(v, OP_Variable, pExpr->iTable, target);
-      if( pExpr->token.n>1 ){
-        sqlite3VdbeChangeP4(v, -1, (char*)pExpr->token.z, pExpr->token.n);
+      int iPrior;
+      VdbeOp *pOp;
+      if( pExpr->token.n<=1
+         && (iPrior = sqlite3VdbeCurrentAddr(v)-1)>=0
+         && (pOp = sqlite3VdbeGetOp(v, iPrior))->opcode==OP_Variable
+         && pOp->p1+pOp->p3==pExpr->iTable
+         && pOp->p2+pOp->p3==target
+         && pOp->p4.z==0
+      ){
+        /* If the previous instruction was a copy of the previous unnamed
+        ** parameter into the previous register, then simply increment the
+        ** repeat count on the prior instruction rather than making a new
+        ** instruction.
+        */
+        pOp->p3++;
+      }else{
+        sqlite3VdbeAddOp3(v, OP_Variable, pExpr->iTable, target, 1);
+        if( pExpr->token.n>1 ){
+          sqlite3VdbeChangeP4(v, -1, (char*)pExpr->token.z, pExpr->token.n);
+        }
       }
       break;
     }