1 /*****************************************************************************/
5 /* Optimize compares */
9 /* (C) 2001-2003 Ullrich von Bassewitz */
10 /* Römerstrasse 52 */
11 /* D-70794 Filderstadt */
12 /* EMail: uz@cc65.org */
15 /* This software is provided 'as-is', without any expressed or implied */
16 /* warranty. In no event will the authors be held liable for any damages */
17 /* arising from the use of this software. */
19 /* Permission is granted to anyone to use this software for any purpose, */
20 /* including commercial applications, and to alter it and redistribute it */
21 /* freely, subject to the following restrictions: */
23 /* 1. The origin of this software must not be misrepresented; you must not */
24 /* claim that you wrote the original software. If you use this software */
25 /* in a product, an acknowledgment in the product documentation would be */
26 /* appreciated but is not required. */
27 /* 2. Altered source versions must be plainly marked as such, and must not */
28 /* be misrepresented as being the original software. */
29 /* 3. This notice may not be removed or altered from any source */
32 /*****************************************************************************/
46 /*****************************************************************************/
48 /*****************************************************************************/
52 /* Table used to invert a condition, indexed by condition */
53 static const unsigned char CmpInvertTab [] = {
55 CMP_LE, CMP_LT, CMP_GE, CMP_GT,
56 CMP_ULE, CMP_ULT, CMP_UGE, CMP_UGT
59 /* Table to show which compares are signed (use the N flag) */
60 static const char CmpSignedTab [] = {
61 0, 0, 1, 1, 1, 1, 0, 0, 0, 0
66 /*****************************************************************************/
67 /* Helper functions */
68 /*****************************************************************************/
72 static void ReplaceCmp (CodeSeg* S, unsigned I, cmp_t Cond)
73 /* Helper function for the replacement of routines that return a boolean
74 * followed by a conditional jump. Instead of the boolean value, the condition
75 * codes are evaluated directly.
76 * I is the index of the conditional branch, the sequence is already checked
84 CodeEntry* E = CS_GetEntry (S, I);
86 /* Replace the conditional branch */
90 CE_ReplaceOPC (E, OP65_JEQ);
94 CE_ReplaceOPC (E, OP65_JNE);
103 if ((N = CS_GetNextEntry (S, I)) == 0) {
105 Internal ("Invalid program flow");
107 L = CS_GenLabel (S, N);
108 N = NewCodeEntry (OP65_BEQ, AM65_BRA, L->Name, L, E->LI);
109 CS_InsertEntry (S, N, I);
110 CE_ReplaceOPC (E, OP65_JPL);
114 CE_ReplaceOPC (E, OP65_JPL);
118 CE_ReplaceOPC (E, OP65_JMI);
126 CE_ReplaceOPC (E, OP65_JMI);
128 N = NewCodeEntry (OP65_JEQ, AM65_BRA, L->Name, L, E->LI);
129 CS_InsertEntry (S, N, I+1);
138 if ((N = CS_GetNextEntry (S, I)) == 0) {
140 Internal ("Invalid program flow");
142 L = CS_GenLabel (S, N);
143 N = NewCodeEntry (OP65_BEQ, AM65_BRA, L->Name, L, E->LI);
144 CS_InsertEntry (S, N, I);
145 CE_ReplaceOPC (E, OP65_JCS);
149 CE_ReplaceOPC (E, OP65_JCS);
153 CE_ReplaceOPC (E, OP65_JCC);
161 CE_ReplaceOPC (E, OP65_JCC);
163 N = NewCodeEntry (OP65_JEQ, AM65_BRA, L->Name, L, E->LI);
164 CS_InsertEntry (S, N, I+1);
168 Internal ("Unknown jump condition: %d", Cond);
176 static int IsImmCmp16 (CodeEntry** L)
177 /* Check if the instructions at L are an immidiate compare of a/x:
182 return (L[0]->OPC == OP65_CPX &&
183 L[0]->AM == AM65_IMM &&
184 (L[0]->Flags & CEF_NUMARG) != 0 &&
185 !CE_HasLabel (L[0]) &&
186 (L[1]->OPC == OP65_JNE || L[1]->OPC == OP65_BNE) &&
188 !CE_HasLabel (L[1]) &&
189 L[2]->OPC == OP65_CMP &&
190 L[2]->AM == AM65_IMM &&
191 (L[2]->Flags & CEF_NUMARG) != 0 &&
192 (L[3]->Info & OF_CBRA) != 0 &&
194 (L[1]->JumpTo->Owner == L[3] || L[1]->JumpTo == L[3]->JumpTo));
199 static int GetCmpRegVal (const CodeEntry* E)
200 /* Return the register value for an immediate compare */
203 case OP65_CMP: return E->RI->In.RegA;
204 case OP65_CPX: return E->RI->In.RegX;
205 case OP65_CPY: return E->RI->In.RegY;
206 default: Internal ("Invalid opcode in GetCmpRegVal");
207 return 0; /* Not reached */
213 /*****************************************************************************/
214 /* Remove calls to the bool transformer subroutines */
215 /*****************************************************************************/
219 unsigned OptBoolTrans (CodeSeg* S)
220 /* Try to remove the call to boolean transformer routines where the call is
224 unsigned Changes = 0;
226 /* Walk over the entries */
228 while (I < CS_GetEntryCount (S)) {
234 CodeEntry* E = CS_GetEntry (S, I);
236 /* Check for a boolean transformer */
237 if (E->OPC == OP65_JSR &&
238 (Cond = FindBoolCmpCond (E->Arg)) != CMP_INV &&
239 (N = CS_GetNextEntry (S, I)) != 0 &&
240 (N->Info & OF_ZBRA) != 0) {
242 /* Make the boolean transformer unnecessary by changing the
243 * the conditional jump to evaluate the condition flags that
244 * are set after the compare directly. Note: jeq jumps if
245 * the condition is not met, jne jumps if the condition is met.
246 * Invert the code if we jump on condition not met.
248 if (GetBranchCond (N->OPC) == BC_EQ) {
249 /* Jumps if condition false, invert condition */
250 Cond = CmpInvertTab [Cond];
253 /* Check if we can replace the code by something better */
254 ReplaceCmp (S, I+1, Cond);
256 /* Remove the call to the bool transformer */
259 /* Remember, we had changes */
269 /* Return the number of changes made */
275 /*****************************************************************************/
276 /* Optimizations for compares */
277 /*****************************************************************************/
281 unsigned OptCmp1 (CodeSeg* S)
282 /* Search for the sequence
294 unsigned Changes = 0;
296 /* Walk over the entries */
298 while (I < CS_GetEntryCount (S)) {
303 CodeEntry* E = CS_GetEntry (S, I);
305 /* Check for the sequence */
306 if (E->OPC == OP65_STX &&
307 !CS_RangeHasLabel (S, I+1, 2) &&
308 CS_GetEntries (S, L, I+1, 2) &&
309 L[0]->OPC == OP65_STX &&
310 strcmp (L[0]->Arg, "tmp1") == 0 &&
311 L[1]->OPC == OP65_ORA &&
312 strcmp (L[1]->Arg, "tmp1") == 0) {
314 /* Remove the remaining instructions */
315 CS_DelEntries (S, I+1, 2);
317 /* Insert the ora instead */
318 CS_InsertEntry (S, NewCodeEntry (OP65_ORA, E->AM, E->Arg, 0, E->LI), I+1);
320 /* Remember, we had changes */
330 /* Return the number of changes made */
336 unsigned OptCmp2 (CodeSeg* S)
339 * lda/and/ora/eor ...
343 * lda/and/ora/eor ...
347 * and remove the cmp.
350 unsigned Changes = 0;
352 /* Walk over the entries */
354 while (I < CS_GetEntryCount (S)) {
359 L[0] = CS_GetEntry (S, I);
361 /* Check for the sequence */
362 if ((L[0]->OPC == OP65_ADC ||
363 L[0]->OPC == OP65_AND ||
364 L[0]->OPC == OP65_ASL ||
365 L[0]->OPC == OP65_DEA ||
366 L[0]->OPC == OP65_EOR ||
367 L[0]->OPC == OP65_INA ||
368 L[0]->OPC == OP65_LDA ||
369 L[0]->OPC == OP65_LSR ||
370 L[0]->OPC == OP65_ORA ||
371 L[0]->OPC == OP65_PLA ||
372 L[0]->OPC == OP65_SBC ||
373 L[0]->OPC == OP65_TXA ||
374 L[0]->OPC == OP65_TYA) &&
375 !CS_RangeHasLabel (S, I+1, 2) &&
376 CS_GetEntries (S, L+1, I+1, 2) &&
377 L[1]->OPC == OP65_CMP &&
378 CE_KnownImm (L[1]) &&
381 /* Check for the call to boolxx. We only remove the compare if
382 * the carry flag is evaluated later, because the load will not
383 * set the carry flag.
385 if (L[2]->OPC == OP65_JSR) {
386 switch (FindBoolCmpCond (L[2]->Arg)) {
394 /* Remove the compare */
395 CS_DelEntry (S, I+1);
410 /* Check for a branch on conditions that are set by the load.
411 * Beware: The insn may branch to another conditional branch
412 * that evaluates other flags, so check that.
417 if ((E->Info & (OF_CBRA|OF_UBRA)) != 0) {
418 /* A conditional branch. Check if it jumps on a
419 * condition not set by the load.
421 if ((E->Info & (OF_FBRA|OF_UBRA)) == 0) {
424 } else if (E->JumpTo == 0) {
425 /* Jump to external */
429 /* Check target of branch */
430 E = E->JumpTo->Owner;
433 /* Some other insn */
439 /* Delete the compare if we can */
441 CS_DelEntry (S, I+1);
452 /* Return the number of changes made */
458 unsigned OptCmp3 (CodeSeg* S)
468 * If a is zero, we may remove the compare. If a and b are both zero, we may
469 * replace it by the sequence
475 * L1 may be either the label at the branch instruction, or the target label
476 * of this instruction.
479 unsigned Changes = 0;
481 /* Walk over the entries */
483 while (I < CS_GetEntryCount (S)) {
488 CodeEntry* E = CS_GetEntry (S, I);
490 /* Check for the sequence */
491 if (E->OPC == OP65_LDA &&
492 CS_GetEntries (S, L, I+1, 5) &&
493 L[0]->OPC == OP65_LDX &&
494 !CE_HasLabel (L[0]) &&
496 !RegAXUsed (S, I+6)) {
498 if ((L[4]->Info & OF_FBRA) != 0 && L[1]->Num == 0 && L[3]->Num == 0) {
499 /* The value is zero, we may use the simple code version. */
500 CE_ReplaceOPC (L[0], OP65_ORA);
501 CS_DelEntries (S, I+2, 3);
503 /* Move the lda instruction after the first branch. This will
504 * improve speed, since the load is delayed after the first
507 CS_MoveEntry (S, I, I+4);
509 /* We will replace the ldx/cpx by lda/cmp */
510 CE_ReplaceOPC (L[0], OP65_LDA);
511 CE_ReplaceOPC (L[1], OP65_CMP);
513 /* Beware: If the first LDA instruction had a label, we have
514 * to move this label to the top of the sequence again.
516 if (CE_HasLabel (E)) {
517 CS_MoveLabels (S, E, L[0]);
530 /* Return the number of changes made */
536 unsigned OptCmp4 (CodeSeg* S)
537 /* Optimize compares of local variables:
547 unsigned Changes = 0;
549 /* Walk over the entries */
551 while (I < CS_GetEntryCount (S)) {
555 /* Get the next entry */
556 L[0] = CS_GetEntry (S, I);
558 /* Check for the sequence */
559 if (L[0]->OPC == OP65_LDY &&
560 CE_KnownImm (L[0]) &&
561 CS_GetEntries (S, L+1, I+1, 5) &&
562 !CE_HasLabel (L[1]) &&
563 CE_IsCallTo (L[1], "ldaxysp") &&
566 if ((L[5]->Info & OF_FBRA) != 0 && L[2]->Num == 0 && L[4]->Num == 0) {
571 /* The value is zero, we may use the simple code version:
578 sprintf (Buf, "$%02X", (int)(L[0]->Num-1));
579 X = NewCodeEntry (OP65_LDY, AM65_IMM, Buf, 0, L[0]->LI);
580 CS_InsertEntry (S, X, I+1);
582 X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
583 CS_InsertEntry (S, X, I+2);
585 X = NewCodeEntry (OP65_LDY, AM65_IMM, L[0]->Arg, 0, L[0]->LI);
586 CS_InsertEntry (S, X, I+3);
588 X = NewCodeEntry (OP65_ORA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
589 CS_InsertEntry (S, X, I+4);
591 CS_DelEntries (S, I+5, 3); /* cpx/bne/cmp */
592 CS_DelEntry (S, I); /* ldy */
599 /* Change the code to just use the A register. Move the load
600 * of the low byte after the first branch if possible:
611 X = NewCodeEntry (OP65_LDY, AM65_IMM, L[0]->Arg, 0, L[0]->LI);
612 CS_InsertEntry (S, X, I+3);
614 X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
615 CS_InsertEntry (S, X, I+4);
617 X = NewCodeEntry (OP65_CMP, L[2]->AM, L[2]->Arg, 0, L[2]->LI);
618 CS_InsertEntry (S, X, I+5);
620 sprintf (Buf, "$%02X", (int)(L[0]->Num-1));
621 X = NewCodeEntry (OP65_LDY, AM65_IMM, Buf, 0, L[0]->LI);
622 CS_InsertEntry (S, X, I+7);
624 X = NewCodeEntry (OP65_LDA, AM65_ZP_INDY, "sp", 0, L[1]->LI);
625 CS_InsertEntry (S, X, I+8);
627 CS_DelEntries (S, I, 3); /* ldy/jsr/cpx */
639 /* Return the number of changes made */
645 unsigned OptCmp5 (CodeSeg* S)
646 /* Search for calls to compare subroutines followed by a conditional branch
647 * and replace them by cheaper versions, since the branch means that the
648 * boolean value returned by these routines is not needed (we may also check
649 * that explicitly, but for the current code generator it is always true).
652 unsigned Changes = 0;
654 /* Walk over the entries */
656 while (I < CS_GetEntryCount (S)) {
662 CodeEntry* E = CS_GetEntry (S, I);
664 /* Check for the sequence */
665 if (E->OPC == OP65_JSR &&
666 (Cond = FindTosCmpCond (E->Arg)) != CMP_INV &&
667 (N = CS_GetNextEntry (S, I)) != 0 &&
668 (N->Info & OF_ZBRA) != 0 &&
671 /* The tos... functions will return a boolean value in a/x and
672 * the Z flag says if this value is zero or not. We will call
673 * a cheaper subroutine instead, one that does not return a
674 * boolean value but only valid flags. Note: jeq jumps if
675 * the condition is not met, jne jumps if the condition is met.
676 * Invert the code if we jump on condition not met.
678 if (GetBranchCond (N->OPC) == BC_EQ) {
679 /* Jumps if condition false, invert condition */
680 Cond = CmpInvertTab [Cond];
683 /* Replace the subroutine call. */
684 E = NewCodeEntry (OP65_JSR, AM65_ABS, "tosicmp", 0, E->LI);
685 CS_InsertEntry (S, E, I+1);
688 /* Replace the conditional branch */
689 ReplaceCmp (S, I+1, Cond);
691 /* Remember, we had changes */
701 /* Return the number of changes made */
707 unsigned OptCmp6 (CodeSeg* S)
708 /* Search for a sequence ldx/txa/branch and remove the txa if A is not
712 unsigned Changes = 0;
714 /* Walk over the entries */
716 while (I < CS_GetEntryCount (S)) {
721 CodeEntry* E = CS_GetEntry (S, I);
723 /* Check for the sequence */
724 if ((E->OPC == OP65_LDX) &&
725 CS_GetEntries (S, L, I+1, 2) &&
726 L[0]->OPC == OP65_TXA &&
727 !CE_HasLabel (L[0]) &&
728 (L[1]->Info & OF_FBRA) != 0 &&
729 !CE_HasLabel (L[1]) &&
730 !RegAUsed (S, I+3)) {
733 CS_DelEntry (S, I+1);
735 /* Remember, we had changes */
745 /* Return the number of changes made */
751 unsigned OptCmp7 (CodeSeg* S)
752 /* Check for register compares where the contents of the register and therefore
753 * the result of the compare is known.
756 unsigned Changes = 0;
759 /* Generate register info for this step */
762 /* Walk over the entries */
764 while (I < CS_GetEntryCount (S)) {
769 CodeEntry* E = CS_GetEntry (S, I);
771 /* Check for a compare against an immediate value */
772 if ((E->Info & OF_CMP) != 0 &&
773 (RegVal = GetCmpRegVal (E)) >= 0 &&
776 /* We are able to evaluate the compare at compile time. Check if
777 * one or more branches are ahead.
779 unsigned JumpsChanged = 0;
781 while ((N = CS_GetNextEntry (S, I)) != 0 && /* Followed by something.. */
782 (N->Info & OF_CBRA) != 0 && /* ..that is a cond branch.. */
783 !CE_HasLabel (N)) { /* ..and has no label */
785 /* Evaluate the branch condition */
787 switch (GetBranchCond (N->OPC)) {
789 Cond = ((unsigned char)RegVal) < ((unsigned char)E->Num);
793 Cond = ((unsigned char)RegVal) >= ((unsigned char)E->Num);
797 Cond = ((unsigned char)RegVal) == ((unsigned char)E->Num);
801 Cond = ((signed char)RegVal) < ((signed char)E->Num);
805 Cond = ((unsigned char)RegVal) != ((unsigned char)E->Num);
809 Cond = ((signed char)RegVal) >= ((signed char)E->Num);
814 /* Not set by the compare operation, bail out (Note:
815 * Just skipping anything here is rather stupid, but
816 * the sequence is never generated by the compiler,
817 * so it's quite safe to skip).
822 Internal ("Unknown branch condition");
826 /* If the condition is false, we may remove the jump. Otherwise
827 * the branch will always be taken, so we may replace it by a
828 * jump (and bail out).
831 CS_DelEntry (S, I+1);
833 CodeLabel* L = N->JumpTo;
834 const char* LabelName = L? L->Name : N->Arg;
835 CodeEntry* X = NewCodeEntry (OP65_JMP, AM65_BRA, LabelName, L, N->LI);
836 CS_InsertEntry (S, X, I+2);
837 CS_DelEntry (S, I+1);
840 /* Remember, we had changes */
845 /* If we have made changes above, we may also remove the compare */
858 /* Free register info */
861 /* Return the number of changes made */