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Simplifications to the expression code generator. Remove about 80 lines of

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older and obsolete code.

FossilOrigin-Name: 53f5cfe11516d0496c7760378b6305c3088d479f
This commit is contained in:
drh
2010-09-27 18:14:12 +00:00
parent 155640552b
commit 7445ffe2da
4 changed files with 18 additions and 91 deletions
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86
src/expr.c
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@@ -2234,73 +2234,6 @@ static int usedAsColumnCache(Parse *pParse, int iFrom, int iTo){
}
#endif /* SQLITE_DEBUG || SQLITE_COVERAGE_TEST */
/*
** If the last instruction coded is an ephemeral copy of any of
** the registers in the nReg registers beginning with iReg, then
** convert the last instruction from OP_SCopy to OP_Copy.
*/
void sqlite3ExprHardCopy(Parse *pParse, int iReg, int nReg){
VdbeOp *pOp;
Vdbe *v;
assert( pParse->db->mallocFailed==0 );
v = pParse->pVdbe;
assert( v!=0 );
pOp = sqlite3VdbeGetOp(v, -1);
assert( pOp!=0 );
if( pOp->opcode==OP_SCopy && pOp->p1>=iReg && pOp->p1<iReg+nReg ){
pOp->opcode = OP_Copy;
}
}
/*
** Generate code to store the value of the iAlias-th alias in register
** target. The first time this is called, pExpr is evaluated to compute
** the value of the alias. The value is stored in an auxiliary register
** and the number of that register is returned. On subsequent calls,
** the register number is returned without generating any code.
**
** Note that in order for this to work, code must be generated in the
** same order that it is executed.
**
** Aliases are numbered starting with 1. So iAlias is in the range
** of 1 to pParse->nAlias inclusive.
**
** pParse->aAlias[iAlias-1] records the register number where the value
** of the iAlias-th alias is stored. If zero, that means that the
** alias has not yet been computed.
*/
static int codeAlias(Parse *pParse, int iAlias, Expr *pExpr, int target){
#if 0
sqlite3 *db = pParse->db;
int iReg;
if( pParse->nAliasAlloc<pParse->nAlias ){
pParse->aAlias = sqlite3DbReallocOrFree(db, pParse->aAlias,
sizeof(pParse->aAlias[0])*pParse->nAlias );
testcase( db->mallocFailed && pParse->nAliasAlloc>0 );
if( db->mallocFailed ) return 0;
memset(&pParse->aAlias[pParse->nAliasAlloc], 0,
(pParse->nAlias-pParse->nAliasAlloc)*sizeof(pParse->aAlias[0]));
pParse->nAliasAlloc = pParse->nAlias;
}
assert( iAlias>0 && iAlias<=pParse->nAlias );
iReg = pParse->aAlias[iAlias-1];
if( iReg==0 ){
if( pParse->iCacheLevel>0 ){
iReg = sqlite3ExprCodeTarget(pParse, pExpr, target);
}else{
iReg = ++pParse->nMem;
sqlite3ExprCode(pParse, pExpr, iReg);
pParse->aAlias[iAlias-1] = iReg;
}
}
return iReg;
#else
UNUSED_PARAMETER(iAlias);
return sqlite3ExprCodeTarget(pParse, pExpr, target);
#endif
}
/*
** Generate code into the current Vdbe to evaluate the given
** expression. Attempt to store the results in register "target".
@@ -2409,7 +2342,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
break;
}
case TK_AS: {
inReg = codeAlias(pParse, pExpr->iTable, pExpr->pLeft, target);
inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
break;
}
#ifndef SQLITE_OMIT_CAST
@@ -3112,17 +3045,12 @@ int sqlite3ExprCodeExprList(
assert( target>0 );
n = pList->nExpr;
for(pItem=pList->a, i=0; i<n; i++, pItem++){
if( pItem->iAlias ){
int iReg = codeAlias(pParse, pItem->iAlias, pItem->pExpr, target+i);
Vdbe *v = sqlite3GetVdbe(pParse);
if( iReg!=target+i ){
sqlite3VdbeAddOp2(v, OP_SCopy, iReg, target+i);
}
}else{
sqlite3ExprCode(pParse, pItem->pExpr, target+i);
}
if( doHardCopy && !pParse->db->mallocFailed ){
sqlite3ExprHardCopy(pParse, target, n);
Expr *pExpr = pItem->pExpr;
int inReg = sqlite3ExprCodeTarget(pParse, pExpr, target+i);
assert( pParse->pVdbe || pParse->db->mallocFailed );
if( inReg!=target+i && pParse->pVdbe ){
sqlite3VdbeAddOp2(pParse->pVdbe, doHardCopy ? OP_Copy : OP_SCopy,
inReg, target+i);
}
}
return n;