Rework the logic that factors constant expressions out of inner loops, making
it both simpler and faster.
FossilOrigin-Name: 8dc5c76c766828d7c28090bec30ff48227e7b140
diff --git a/src/expr.c b/src/expr.c
index 7e72b44..524f24c 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -2989,15 +2989,42 @@
** If the register is a temporary register that can be deallocated,
** then write its number into *pReg. If the result register is not
** a temporary, then set *pReg to zero.
+**
+** If pExpr is a constant, then this routine might generate this
+** code to fill the register in the initialization section of the
+** VDBE program, in order to factor it out of the evaluation loop.
*/
int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){
- int r1 = sqlite3GetTempReg(pParse);
- int r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
- if( r2==r1 ){
- *pReg = r1;
+ int r2;
+ pExpr = sqlite3ExprSkipCollate(pExpr);
+ if( pParse->cookieGoto>0
+ && pParse->nMem<32768
+ && pExpr->op!=TK_REGISTER
+ && sqlite3ExprIsConstantNotJoin(pExpr)
+ ){
+ ExprList *p = pParse->pConstExpr;
+ int i;
+ *pReg = 0;
+ if( p ){
+ for(i=0; i<p->nExpr; i++){
+ if( sqlite3ExprCompare(p->a[i].pExpr, pExpr, -1)==0 ){
+ return p->a[i].iAlias;
+ }
+ }
+ }
+ p = sqlite3ExprListAppend(pParse, p, sqlite3ExprDup(pParse->db, pExpr, 0));
+ pParse->pConstExpr = p;
+ r2 = ++pParse->nMem;
+ if( p ) p->a[p->nExpr-1].iAlias = r2;
}else{
- sqlite3ReleaseTempReg(pParse, r1);
- *pReg = 0;
+ int r1 = sqlite3GetTempReg(pParse);
+ r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
+ if( r2==r1 ){
+ *pReg = r1;
+ }else{
+ sqlite3ReleaseTempReg(pParse, r1);
+ *pReg = 0;
+ }
}
return r2;
}
@@ -3329,140 +3356,6 @@
#endif /* SQLITE_DEBUG */
/*
-** Return TRUE if pExpr is an constant expression that is appropriate
-** for factoring out of a loop. Appropriate expressions are:
-**
-** * Any expression that evaluates to two or more opcodes.
-**
-** * Any OP_Integer, OP_Real, OP_String, OP_Blob, OP_Null,
-** or OP_Variable that does not need to be placed in a
-** specific register.
-**
-** There is no point in factoring out single-instruction constant
-** expressions that need to be placed in a particular register.
-** We could factor them out, but then we would end up adding an
-** OP_SCopy instruction to move the value into the correct register
-** later. We might as well just use the original instruction and
-** avoid the OP_SCopy.
-*/
-static int isAppropriateForFactoring(Expr *p){
- if( !sqlite3ExprIsConstantNotJoin(p) ){
- return 0; /* Only constant expressions are appropriate for factoring */
- }
- if( (p->flags & EP_FixedDest)==0 ){
- return 1; /* Any constant without a fixed destination is appropriate */
- }
- while( p->op==TK_UPLUS ) p = p->pLeft;
- switch( p->op ){
-#ifndef SQLITE_OMIT_BLOB_LITERAL
- case TK_BLOB:
-#endif
- case TK_VARIABLE:
- case TK_INTEGER:
- case TK_FLOAT:
- case TK_NULL:
- case TK_STRING: {
- testcase( p->op==TK_BLOB );
- testcase( p->op==TK_VARIABLE );
- testcase( p->op==TK_INTEGER );
- testcase( p->op==TK_FLOAT );
- testcase( p->op==TK_NULL );
- testcase( p->op==TK_STRING );
- /* Single-instruction constants with a fixed destination are
- ** better done in-line. If we factor them, they will just end
- ** up generating an OP_SCopy to move the value to the destination
- ** register. */
- return 0;
- }
- case TK_UMINUS: {
- if( p->pLeft->op==TK_FLOAT || p->pLeft->op==TK_INTEGER ){
- return 0;
- }
- break;
- }
- default: {
- break;
- }
- }
- return 1;
-}
-
-/*
-** If pExpr is a constant expression that is appropriate for
-** factoring out of a loop, then evaluate the expression
-** into a register and convert the expression into a TK_REGISTER
-** expression.
-*/
-static int evalConstExpr(Walker *pWalker, Expr *pExpr){
- Parse *pParse = pWalker->pParse;
- switch( pExpr->op ){
- case TK_IN:
- case TK_REGISTER: {
- return WRC_Prune;
- }
- case TK_COLLATE: {
- return WRC_Continue;
- }
- case TK_FUNCTION:
- case TK_AGG_FUNCTION:
- case TK_CONST_FUNC: {
- /* The arguments to a function have a fixed destination.
- ** Mark them this way to avoid generated unneeded OP_SCopy
- ** instructions.
- */
- ExprList *pList = pExpr->x.pList;
- assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
- if( pList ){
- int i = pList->nExpr;
- struct ExprList_item *pItem = pList->a;
- for(; i>0; i--, pItem++){
- if( ALWAYS(pItem->pExpr) ) pItem->pExpr->flags |= EP_FixedDest;
- }
- }
- break;
- }
- }
- if( isAppropriateForFactoring(pExpr) ){
- int r1 = ++pParse->nMem;
- int r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
- /* If r2!=r1, it means that register r1 is never used. That is harmless
- ** but suboptimal, so we want to know about the situation to fix it.
- ** Hence the following assert: */
- assert( r2==r1 );
- exprToRegister(pExpr, r2);
- return WRC_Prune;
- }
- return WRC_Continue;
-}
-
-/*
-** Preevaluate constant subexpressions within pExpr and store the
-** results in registers. Modify pExpr so that the constant subexpresions
-** are TK_REGISTER opcodes that refer to the precomputed values.
-**
-** This routine is a no-op if the jump to the cookie-check code has
-** already occur. Since the cookie-check jump is generated prior to
-** any other serious processing, this check ensures that there is no
-** way to accidently bypass the constant initializations.
-**
-** This routine is also a no-op if the SQLITE_FactorOutConst optimization
-** is disabled via the sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS)
-** interface. This allows test logic to verify that the same answer is
-** obtained for queries regardless of whether or not constants are
-** precomputed into registers or if they are inserted in-line.
-*/
-void sqlite3ExprCodeConstants(Parse *pParse, Expr *pExpr){
- Walker w;
- if( pParse->cookieGoto ) return;
- if( OptimizationDisabled(pParse->db, SQLITE_FactorOutConst) ) return;
- memset(&w, 0, sizeof(w));
- w.xExprCallback = evalConstExpr;
- w.pParse = pParse;
- sqlite3WalkExpr(&w, pExpr);
-}
-
-
-/*
** Generate code that pushes the value of every element of the given
** expression list into a sequence of registers beginning at target.
**
@@ -3863,7 +3756,7 @@
if( pA->iColumn!=pB->iColumn ) return 2;
if( pA->iTable!=pB->iTable
&& pA->op!=TK_REGISTER
- && (pA->iTable!=iTab || NEVER(pB->iTable>=0)) ) return 2;
+ && (pA->iTable!=iTab || pB->iTable>=0) ) return 2;
if( ExprHasProperty(pA, EP_IntValue) ){
if( !ExprHasProperty(pB, EP_IntValue) || pA->u.iValue!=pB->u.iValue ){
return 2;