#include "common.h"
-/*-----------------------------------------------------------------*/
-/* pointerArithOpts - does some pointer arithmetic operations */
-/*-----------------------------------------------------------------*/
- int pointerArithOpts (iCode *ic, hTab *ptrs)
+/*-----------------------------------------------------------------------*/
+/* findPointerGetSet - find the pointer get or set for a operand */
+/*-----------------------------------------------------------------------*/
+static iCode *findPointerGetSet(iCode *sic,operand *op)
{
- operand *asym ;
- long cval;
- hashtItem *htip;
- induction *ip ;
- int lr = 0 ;
-
- /* the aim here is to reduce the arithmetics performed */
- /* during repeated pointer access . for eg. there are */
- /* lot of places the code generated looks like this */
- /* iTempNN = &[somevar] */
- /* iTempNX = iTempNN + constant-1 */
- /* *(iTempNX) := somevalue */
- /* iTempNY = iTempNN + constant-2 */
- /* *(iTempNY) := somevalue */
- /* we want to change this sequence to */
- /* iTempNN = &[somevar] */
- /* iTempNN = iTempNN + constant-1 */
- /* (*iTempNN) := someValue */
- /* WHY ? this will reduce the number of definitions */
- /* as well as help us in register allocation */
-
- /* first check if +/- */
- if (ic->op != '+' && ic->op != '-' )
- return 0;
-
- /* if the result is not an iTemp */
- if (!IS_ITEMP(IC_RESULT(ic)))
- return 0;
-
- /* if +/- then check if one of them is literal */
- if (! IS_OP_LITERAL(IC_LEFT(ic)) &&
- ! IS_OP_LITERAL(IC_RIGHT(ic)) )
- return 0;
-
- /* get the operand & literal value */
- if (IS_OP_LITERAL(IC_LEFT(ic))) {
- cval = operandLitValue(IC_LEFT(ic));
- asym = IC_RIGHT(ic) ;
- } else {
- cval = operandLitValue(IC_RIGHT(ic)) ;
- lr++ ;
- asym = IC_LEFT(ic);
- }
+ iCode *ic = sic;
- /* if this symbol does not exist the address of */
- /* or if the symbol is the same as the result */
- if (asym->key == IC_RESULT(ic)->key ||
- (htip = hTabSearch(ptrs,asym->key)) == NULL )
- return 0;
-
- ip = htip->item;
+ for (; ic ; ic = ic->next) {
+ if ((POINTER_SET(ic) && isOperandEqual(op,IC_RESULT(ic))) ||
+ (POINTER_GET(ic) && isOperandEqual(op,IC_LEFT(ic))))
+ return ic;
+
+ /* if we find any other usage or definition of op null */
+ if (IC_RESULT(ic) && isOperandEqual(IC_RESULT(ic),op))
+ return NULL;
+
+ if (IC_RIGHT(ic) && isOperandEqual(IC_RIGHT(ic),op))
+ return NULL;
+
+ if (IC_LEFT(ic) && isOperandEqual(IC_LEFT(ic),op))
+ return NULL;
-
- /* if the constant value in induction is zero */
- /* then we just change the operand */
- if (ip->cval == 0) {
- ip->asym = IC_RESULT(ic) ;
- ip->cval = cval ; /* update the offset info */
- return 0;
- }
- /* we can do the substitution */
- replaceAllSymBySym (ic->next, IC_RESULT(ic),ip->asym);
- IC_RESULT(ic) = operandFromOperand(ip->asym);
-
- /* now we know that the constant value is greater than zero */
- /* we have to do some arithmetic here : if the offset is greater */
- /* than what we want then rechange it to subtraction */
- if ( ip->cval > cval) {
- ic->op = '-' ;
- if (lr) {
- IC_LEFT(ic) = operandFromOperand(ip->asym);
- IC_RIGHT(ic) = operandFromLit(ip->cval - cval);
- }
- else {
- IC_RIGHT(ic) = operandFromOperand(ip->asym);
- IC_LEFT(ic) = operandFromLit(ip->cval - cval);
- }
- } else {
- if (lr) {
- IC_LEFT(ic) = operandFromOperand(ip->asym);
- IC_RIGHT(ic) = operandFromLit(cval - ip->cval);
- }
- else {
- IC_RIGHT(ic) = operandFromOperand (ip->asym);
- IC_LEFT(ic) = operandFromLit(cval - ip->cval);
- }
}
-
- ip->cval = cval ;
- return 1;
+
+ return NULL;
}
-/*-----------------------------------------------------------------*/
-/* ptrAopts - pointer arithmetic optimizations for a basic block */
-/*-----------------------------------------------------------------*/
-void ptrAopts (eBBlock **ebbs, int count)
+/*-----------------------------------------------------------------------*/
+/* ptrPostIncDecOpts - will do some pointer post increment optimizations */
+/* this will help register allocation amongst others */
+/*-----------------------------------------------------------------------*/
+void ptrPostIncDecOpt (iCode *sic)
{
- int i;
-
- hTab *pointers ;
-
- /* for each basic block do */
- for (i = 0 ; i < count ; i++ ) {
- iCode *ic;
-
- setToNull((void **) &pointers);
- /* iterate thru intructions in the basic block */
- for (ic = ebbs[i]->sch ; ic ; ic = ic->next ) {
-
- if (SKIP_IC(ic) ||ic->op == IFX)
- continue ;
-
- if (pointers)
- pointerArithOpts(ic,pointers);
-
- if (!POINTER_SET(ic) && IC_RESULT(ic))
- /* delete from pointer access */
- hTabDeleteItem (&pointers, IC_RESULT(ic)->key,NULL,DELETE_CHAIN,NULL);
-
- /* set up for pointers */
- if ((ic->op == ADDRESS_OF || ADD_SUBTRACT_ITEMP(ic)) &&
- IS_ITEMP(IC_RESULT(ic)) ) {
- operand *sym ;
- operand *asym ;
- long cval ;
-
- if ( ic->op == ADDRESS_OF){
- sym = IC_RESULT(ic);
- asym = NULL ;
- cval = 0;
- } else {
- sym = IC_LEFT(ic);
- asym = IC_RESULT(ic);
- cval = operandLitValue(IC_RIGHT(ic));
- }
-
- /* put it in the pointer set */
- }
- }
-
- }
+ /* this is what we do. look for sequences like
+
+ iTempX := _SOME_POINTER_;
+ iTempY := _SOME_POINTER_ + nn ; nn = sizeof (pointed to object)
+ _SOME_POINTER_ := iTempY;
+ either
+ iTempZ := @[iTempX];
+ or
+ *(iTempX) := ..something..
+ if we find this then transform this to
+ iTempX := _SOME_POINTER_;
+ either
+ iTempZ := @[iTempX];
+ or
+ *(iTempX) := ..something..
+ iTempY := _SOME_POINTER_ + nn ; nn = sizeof (pointed to object)
+ _SOME_POINTER_ := iTempY; */
+
+ /* sounds simple enough so lets start , here I use -ve
+ tests all the way to return if any test fails */
+ iCode *pgs, *sh,*st;
+
+ if (!( sic->next && sic->next->next && sic->next->next->next))
+ return ;
+ if (sic->next->op != '+' && sic->next->op != '-') return;
+ if (!(sic->next->next->op == '=' &&
+ !POINTER_SET(sic->next->next))) return;
+ if (!isOperandEqual(IC_LEFT(sic->next),IC_RIGHT(sic)) ||
+ !IS_OP_LITERAL(IC_RIGHT(sic->next)) ) return;
+ if (operandLitValue(IC_RIGHT(sic->next)) !=
+ getSize(operandType(IC_RIGHT(sic))->next)) return;
+ if (!isOperandEqual(IC_RESULT(sic->next->next),
+ IC_RIGHT(sic))) return;
+ if (!isOperandEqual(IC_RESULT(sic->next),IC_RIGHT(sic->next->next))) return;
+ if (!(pgs = findPointerGetSet(sic->next->next,IC_RESULT(sic))))
+ return;
+
+ /* found the patter .. now do the transformation */
+ sh = sic->next; st = sic->next->next ;
+
+ /* take the two out of the chain */
+ sic->next = st->next;
+ st->next->prev = sic;
+
+ /* and put them after the pointer get/set icode */
+ if ((st->next = pgs->next))
+ st->next->prev = st;
+ pgs->next = sh;
+ sh->prev = pgs;
+
}
projects / fw / sdcc / commitdiff