mirror of https://github.com/cc65/cc65.git
231 lines
7.2 KiB
C
231 lines
7.2 KiB
C
/*****************************************************************************/
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/* */
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/* coptsub.c */
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/* */
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/* Optimize subtraction sequences */
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/* */
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/* */
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/* */
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/* (C) 2001-2006, Ullrich von Bassewitz */
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/* Roemerstrasse 52 */
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/* D-70794 Filderstadt */
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/* EMail: uz@cc65.org */
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/* */
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/* */
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/* This software is provided 'as-is', without any expressed or implied */
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/* warranty. In no event will the authors be held liable for any damages */
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/* arising from the use of this software. */
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/* */
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/* Permission is granted to anyone to use this software for any purpose, */
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/* including commercial applications, and to alter it and redistribute it */
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/* freely, subject to the following restrictions: */
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/* */
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/* 1. The origin of this software must not be misrepresented; you must not */
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/* claim that you wrote the original software. If you use this software */
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/* in a product, an acknowledgment in the product documentation would be */
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/* appreciated but is not required. */
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/* 2. Altered source versions must be plainly marked as such, and must not */
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/* be misrepresented as being the original software. */
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/* 3. This notice may not be removed or altered from any source */
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/* distribution. */
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/* */
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/*****************************************************************************/
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/* common */
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#include "chartype.h"
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/* cc65 */
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#include "codeent.h"
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#include "codeinfo.h"
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#include "coptsub.h"
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/*****************************************************************************/
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/* Optimize subtractions */
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/*****************************************************************************/
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unsigned OptSub1 (CodeSeg* S)
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/* Search for the sequence
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**
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** sbc ...
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** bcs L
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** dex
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** L:
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**
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** and remove the handling of the high byte if X is not used later.
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*/
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{
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unsigned Changes = 0;
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/* Walk over the entries */
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unsigned I = 0;
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while (I < CS_GetEntryCount (S)) {
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CodeEntry* L[3];
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/* Get next entry */
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CodeEntry* E = CS_GetEntry (S, I);
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/* Check for the sequence */
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if (E->OPC == OP65_SBC &&
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CS_GetEntries (S, L, I+1, 3) &&
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(L[0]->OPC == OP65_BCS || L[0]->OPC == OP65_JCS) &&
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L[0]->JumpTo != 0 &&
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!CE_HasLabel (L[0]) &&
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L[1]->OPC == OP65_DEX &&
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!CE_HasLabel (L[1]) &&
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L[0]->JumpTo->Owner == L[2] &&
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!RegXUsed (S, I+3)) {
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/* Remove the bcs/dex */
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CS_DelEntries (S, I+1, 2);
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/* Remember, we had changes */
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++Changes;
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}
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/* Next entry */
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++I;
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}
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/* Return the number of changes made */
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return Changes;
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}
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unsigned OptSub2 (CodeSeg* S)
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/* Search for the sequence
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**
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** lda xx
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** sec
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** sta tmp1
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** lda yy
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** sbc tmp1
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** sta yy
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**
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** and replace it by
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**
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** sec
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** lda yy
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** sbc xx
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** sta yy
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*/
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{
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unsigned Changes = 0;
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/* Walk over the entries */
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unsigned I = 0;
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while (I < CS_GetEntryCount (S)) {
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CodeEntry* L[5];
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/* Get next entry */
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CodeEntry* E = CS_GetEntry (S, I);
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/* Check for the sequence */
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if (E->OPC == OP65_LDA &&
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!CS_RangeHasLabel (S, I+1, 5) &&
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CS_GetEntries (S, L, I+1, 5) &&
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L[0]->OPC == OP65_SEC &&
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L[1]->OPC == OP65_STA &&
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strcmp (L[1]->Arg, "tmp1") == 0 &&
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L[2]->OPC == OP65_LDA &&
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L[3]->OPC == OP65_SBC &&
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strcmp (L[3]->Arg, "tmp1") == 0 &&
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L[4]->OPC == OP65_STA &&
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strcmp (L[4]->Arg, L[2]->Arg) == 0) {
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/* Remove the store to tmp1 */
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CS_DelEntry (S, I+2);
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/* Remove the subtraction */
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CS_DelEntry (S, I+3);
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/* Move the lda to the position of the subtraction and change the
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** op to SBC.
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*/
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CS_MoveEntry (S, I, I+3);
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CE_ReplaceOPC (E, OP65_SBC);
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/* If the sequence head had a label, move this label back to the
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** head.
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*/
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if (CE_HasLabel (E)) {
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CS_MoveLabels (S, E, L[0]);
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}
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/* Remember, we had changes */
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++Changes;
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}
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/* Next entry */
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++I;
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}
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/* Return the number of changes made */
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return Changes;
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}
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unsigned OptSub3 (CodeSeg* S)
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/* Search for a call to decaxn and replace it by an 8 bit sub if the X register
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** is not used later.
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*/
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{
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unsigned Changes = 0;
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/* Walk over the entries */
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unsigned I = 0;
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while (I < CS_GetEntryCount (S)) {
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CodeEntry* E;
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/* Get next entry */
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E = CS_GetEntry (S, I);
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/* Check for the sequence */
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if (E->OPC == OP65_JSR &&
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strncmp (E->Arg, "decax", 5) == 0 &&
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IsDigit (E->Arg[5]) &&
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E->Arg[6] == '\0' &&
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!RegXUsed (S, I+1)) {
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CodeEntry* X;
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const char* Arg;
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/* Insert new code behind the sequence */
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X = NewCodeEntry (OP65_SEC, AM65_IMP, 0, 0, E->LI);
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CS_InsertEntry (S, X, I+1);
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Arg = MakeHexArg (E->Arg[5] - '0');
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X = NewCodeEntry (OP65_SBC, AM65_IMM, Arg, 0, E->LI);
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CS_InsertEntry (S, X, I+2);
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/* Delete the old code */
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CS_DelEntry (S, I);
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/* Remember, we had changes */
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++Changes;
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}
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/* Next entry */
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++I;
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}
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/* Return the number of changes made */
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return Changes;
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}
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