[Bug c/12362] New: Compiler generates incorrect code at -O2

["sean at mcneil dot com" <gcc-bugzilla at gcc dot gnu dot org>]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12362

           Summary: Compiler generates incorrect code at -O2
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sean at mcneil dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i386-unknown-freebsd4.9
GCC target triplet: mips-wrs-vxworks

The following code compiled with

mips-wrs-vxworks-gcc -c -O2 early.c

produces erroneous code.  It is essentially returning within the if statement
instead of falling through to complete the function.

early.c:

#define EARLY 4

typedef struct 
{
    int status;
    int node;
} ID;

typedef int (*FUNCPTR) ();

typedef struct
{
    FUNCPTR removeRtn;
    FUNCPTR calibrateRtn;
    FUNCPTR putRtn;
} Q_CLASS;

typedef struct
{
    Q_CLASS *pQClass;
} Q_HEAD;

typedef int Q_NODE;

extern int ticks;
extern ID *id;
extern Q_HEAD queue;
extern Q_HEAD t_queue;

#define Q_REMOVE(pQHead,pQNode)						\
    (*(((Q_HEAD *)(pQHead))->pQClass->removeRtn))			\
    (((Q_HEAD *)(pQHead)), ((Q_NODE *)(pQNode)))

#define Q_CALIBRATE(pQHead,keyDelta)					\
    (*(((Q_HEAD *)(pQHead))->pQClass->calibrateRtn))			\
    (((Q_HEAD *)(pQHead)), ((int)(keyDelta)))

#define Q_PUT(pQHead,pQNode,key)					\
    (*(((Q_HEAD *)(pQHead))->pQClass->putRtn))				\
    (((Q_HEAD *)(pQHead)), ((Q_NODE *)(pQNode)), (key))

int early (register int timeout)
{
    Q_REMOVE (&queue, id);

    if ((unsigned)(ticks + timeout) < ticks)
    {
	Q_CALIBRATE (&t_queue, ~ticks + 1);
	ticks = 0;
    }

    Q_PUT (&queue, &id->node, timeout + ticks);
    id->status |= EARLY;

    return 0;
}