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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/55377] ipa-pure-cont produces wrong code on AVR Date: Mon, 19 Nov 2012 04:37:00 -0000 [thread overview] Message-ID: <bug-55377-4-oxcc41uzTK@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-55377-4@http.gcc.gnu.org/bugzilla/> 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.
prev parent reply other threads:[~2012-11-19 4:37 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-11-18 12:41 [Bug c++/55377] New: " gcc@d-silva.org 2012-11-19 4:37 ` pinskia at gcc dot gnu.org [this message]
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