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Remove unnecessary transfer instructions.

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git-svn-id: svn://svn.cc65.org/cc65/trunk@4011 b7a2c559-68d2-44c3-8de9-860c34a00d81
This commit is contained in:
uz 2009-08-15 12:49:15 +00:00
parent b68db83a2b
commit 14f213cadb
3 changed files with 182 additions and 6 deletions
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3
src/cc65/codeopt.c
View File

@ -1019,6 +1019,7 @@ static OptFunc DOptSub3 = { OptSub3, "OptSub3", 100, 0,
static OptFunc DOptTest1 = { OptTest1, "OptTest1", 100, 0, 0, 0, 0, 0 };
static OptFunc DOptTransfers1 = { OptTransfers1, "OptTransfers1", 0, 0, 0, 0, 0, 0 };
static OptFunc DOptTransfers2 = { OptTransfers2, "OptTransfers2", 60, 0, 0, 0, 0, 0 };
static OptFunc DOptTransfers3 = { OptTransfers3, "OptTransfers3", 65, 0, 0, 0, 0, 0 };
static OptFunc DOptUnusedLoads = { OptUnusedLoads, "OptUnusedLoads", 0, 0, 0, 0, 0, 0 };
static OptFunc DOptUnusedStores = { OptUnusedStores, "OptUnusedStores", 0, 0, 0, 0, 0, 0 };
@ -1095,6 +1096,7 @@ static OptFunc* OptFuncs[] = {
&DOptTest1,
&DOptTransfers1,
&DOptTransfers2,
&DOptTransfers3,
&DOptUnusedLoads,
&DOptUnusedStores,
};
@ -1425,6 +1427,7 @@ static unsigned RunOptGroup3 (CodeSeg* S)
C += RunOptFunc (S, &DOptDupLoads, 1);
C += RunOptFunc (S, &DOptStoreLoad, 1);
C += RunOptFunc (S, &DOptTransfers1, 1);
C += RunOptFunc (S, &DOptTransfers3, 1);
C += RunOptFunc (S, &DOptStore1, 1);
C += RunOptFunc (S, &DOptStore5, 1);
C += RunOptFunc (S, &DOptPushPop, 1);

172
src/cc65/coptind.c
View File

@ -6,8 +6,8 @@
/* */
/* */
/* */
/* (C) 2001-2005, Ullrich von Bassewitz */
/* Römerstraße 52 */
/* (C) 2001-2009, Ullrich von Bassewitz */
/* Roemerstrasse 52 */
/* D-70794 Filderstadt */
/* EMail: uz@cc65.org */
/* */
@ -1234,6 +1234,169 @@ unsigned OptTransfers2 (CodeSeg* S)
unsigned OptTransfers3 (CodeSeg* S)
/* Replace a register transfer followed by a store of the second register by a
* store of the first register if this is possible.
*/
{
unsigned Changes = 0;
unsigned Xfer = 0; /* Index of transfer insn */
unsigned Store = 0; /* Index of store insn */
CodeEntry* XferEntry = 0; /* Pointer to xfer insn */
CodeEntry* StoreEntry = 0; /* Pointer to store insn */
enum {
Searching,
FoundXfer,
FoundStore
} State = Searching;
/* Walk over the entries. Look for a xfer instruction that is followed by
* a store later, where the value of the register is not used later.
*/
unsigned I = 0;
while (I < CS_GetEntryCount (S)) {
/* Get next entry */
CodeEntry* E = CS_GetEntry (S, I);
switch (State) {
case Searching:
if (E->Info & OF_XFR) {
/* Found start of sequence */
Xfer = I;
XferEntry = E;
State = FoundXfer;
}
break;
case FoundXfer:
/* If we find a conditional jump, abort the sequence, since
* handling them makes things really complicated.
*/
if (E->Info & OF_CBRA) {
/* Switch back to searching */
I = Xfer;
State = Searching;
/* Does this insn use the target register of the transfer? */
} else if ((E->Use & XferEntry->Chg) != 0) {
/* It it's a store instruction, and the block is a basic
* block, proceed. Otherwise restart
*/
if ((E->Info & OF_STORE) != 0 &&
CS_IsBasicBlock (S, Xfer, I)) {
Store = I;
StoreEntry = E;
State = FoundStore;
} else {
I = Xfer;
State = Searching;
}
/* Does this insn change the target register of the transfer? */
} else if (E->Chg & XferEntry->Chg) {
/* We *may* add code here to remove the transfer, but I'm
* currently not sure about the consequences, so I won't
* do that and bail out instead.
*/
I = Xfer;
State = Searching;
}
break;
case FoundStore:
/* We are at the instruction behind the store. If the register
* isn't used later, and we have an address mode match, we can
* replace the transfer by a store and remove the store here.
*/
if ((GetRegInfo (S, I, XferEntry->Chg) & XferEntry->Chg) == 0 &&
(StoreEntry->AM == AM65_ABS || StoreEntry->AM == AM65_ZP) &&
!MemAccess (S, Xfer+1, Store-1, E->Arg)) {
/* Generate the replacement store insn */
CodeEntry* X = 0;
switch (XferEntry->OPC) {
case OP65_TXA:
X = NewCodeEntry (OP65_STX,
StoreEntry->AM,
StoreEntry->Arg,
0,
StoreEntry->LI);
break;
case OP65_TAX:
X = NewCodeEntry (OP65_STA,
StoreEntry->AM,
StoreEntry->Arg,
0,
StoreEntry->LI);
break;
case OP65_TYA:
X = NewCodeEntry (OP65_STY,
StoreEntry->AM,
StoreEntry->Arg,
0,
StoreEntry->LI);
break;
case OP65_TAY:
X = NewCodeEntry (OP65_STA,
StoreEntry->AM,
StoreEntry->Arg,
0,
StoreEntry->LI);
break;
default:
break;
}
/* If we have a replacement store, change the code */
if (X) {
/* Insert before the xfer insn */
CS_InsertEntry (S, X, Xfer);
/* Remove the xfer instead */
CS_DelEntry (S, Xfer+1);
/* Remove the final store */
CS_DelEntry (S, Store);
/* Correct I so we continue with the next insn */
I -= 2;
/* Remember we had changes */
++Changes;
} else {
/* Restart after last xfer insn */
I = Xfer;
}
} else {
/* Restart after last xfer insn */
I = Xfer;
}
State = Searching;
break;
}
/* Next entry */
++I;
}
/* Return the number of changes made */
return Changes;
}
unsigned OptPushPop (CodeSeg* S)
/* Remove a PHA/PLA sequence were A is not used later */
{
@ -1315,6 +1478,9 @@ unsigned OptPushPop (CodeSeg* S)
/* Remove the PLA/STA sequence */
CS_DelEntries (S, Pop, 2);
/* Correct I so we continue with the next insn */
I -= 2;
/* Remember we had changes */
++Changes;
@ -1324,8 +1490,10 @@ unsigned OptPushPop (CodeSeg* S)
/* We can remove the PHA and PLA instructions */
CS_DelEntry (S, Pop);
CS_DelEntry (S, Push);
/* Correct I so we continue with the next insn */
I -= 2;
/* Remember we had changes */
++Changes;

13
src/cc65/coptind.h
View File

@ -6,10 +6,10 @@
/* */
/* */
/* */
/* (C) 2001-2003 Ullrich von Bassewitz */
/* Römerstrasse 52 */
/* D-70794 Filderstadt */
/* EMail: uz@cc65.org */
/* (C) 2001-2009, Ullrich von Bassewitz */
/* Roemerstrasse 52 */
/* D-70794 Filderstadt */
/* EMail: uz@cc65.org */
/* */
/* */
/* This software is provided 'as-is', without any expressed or implied */
@ -110,6 +110,11 @@ unsigned OptTransfers2 (CodeSeg* S);
* register if possible.
*/
unsigned OptTransfers3 (CodeSeg* S);
/* Replace a register transfer followed by a store of the second register by a
* store of the first register if this is possible.
*/
unsigned OptPushPop (CodeSeg* S);
/* Remove a PHA/PLA sequence were A is not used later */