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OptCmp3 removed a compare to zero instruction preceeded by a load despite the

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fact that the carry flag (which is set by the compare but not by the load) had
been used later.


git-svn-id: svn://svn.cc65.org/cc65/trunk@5885 b7a2c559-68d2-44c3-8de9-860c34a00d81
This commit is contained in:
uz 2012-10-28 19:04:09 +00:00
parent f90fa9cc29
commit ff166363f0
1 changed files with 23 additions and 6 deletions
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29
src/cc65/coptcmp.c
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@ -432,8 +432,8 @@ unsigned OptCmp3 (CodeSeg* S)
int Delete = 0;
/* Check for the call to boolxx. We only remove the compare if
* the carry flag is evaluated later, because the load will not
* set the carry flag.
* the carry flag is not evaluated later, because the load will
* not set the carry flag.
*/
if (L[2]->OPC == OP65_JSR) {
switch (FindBoolCmpCond (L[2]->Arg)) {
@ -458,12 +458,29 @@ unsigned OptCmp3 (CodeSeg* S)
}
} else if ((L[2]->Info & OF_FBRA) != 0) {
/* The following insn branches on the condition of a load, so
* the compare instruction can be removed.
/* The following insn branches on the condition of the load,
* so the compare instruction might be removed. For safety,
* do some more checks if the carry isn't used later, since
* the compare does set the carry, but the load does not.
*/
Delete = 1;
CodeEntry* E;
CodeEntry* N;
if ((E = CS_GetNextEntry (S, I+2)) != 0 &&
L[2]->JumpTo != 0 &&
(N = L[2]->JumpTo->Owner) != 0 &&
N->OPC != OP65_BCC &&
N->OPC != OP65_BCS &&
N->OPC != OP65_JCC &&
N->OPC != OP65_JCS &&
(N->OPC != OP65_JSR ||
FindBoolCmpCond (N->Arg) == CMP_INV)) {
/* The following insn branches on the condition of a load,
* and there's no use of the carry flag in sight, so the
* compare instruction can be removed.
*/
Delete = 1;
}
}
/* Delete the compare if we can */