http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55377
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-11-19
04:36:36 UTC ---
This looks correct as the only thing as:
while (!serial.canWrite()) {}
cannot change its state once in that loop as far as I can tell. There are no
volatile variables read either.
canWrite is inlined which was:
bool canWrite() {
return !(_txPointers.full(sizeof(TXBuffer)));
}
And we decided mhvlib::RingBuffer::full only reads from its arguments which are
not volatile.
full does:
bool full(uint8_t blockLength) {
return length() > (_size - 1 - blockLength);
}
Where length was:
uint8_t length() {
int16_t length = _head - _tail;
if (length < 0) {
length = (_size - _tail) + _head + 1;
}
return (uint8_t) length;
}
And both _head and _tail are not marked as volatile so we only need to read
them once (including through the loop).
So the code that ipa-pure-const is producing is correct.
The reason why you can't produce a simpler testcase is because it depends on
other optimization chooses that the compiler has decided to take.
So in conclusion, I think you are missing some variables marked as volatile in
the RingBuffer implementation and/or Device_TXImplementation implementation.
