Hi,
While upgrading a port of mine to trunk for a testcase I noticed the
following . Its more of a question for a language lawyer I guess.
The test looks like this.
int spinlock[2];
void foo (void)
{
volatile int * spinlock0;
while (*spinlock0 == 0)
{
/* do nothing */
}
}
Store CCP folds away the assignment in the following way :
Folded statement: *spinlock0_1 = 0;
into: spinlock[0] = 0;
Folded statement: *spinlock1_2 = 0;
into: spinlock[1] = 0;
Folded statement: D.1498_3 = *spinlock0_1;
into: D.1498_3 = spinlock[0];
main ()
{
volatile int * spinlock1;
volatile int * spinlock0;
int D.1498;
<bb 2>:
spinlock0_1 = &spinlock[0];
spinlock1_2 = &spinlock[1];
spinlock[0] = 0;
spinlock[1] = 0;
<bb 3>:
D.1498_3 = spinlock[0];
if (D.1498_3 != 0)
goto <bb 3>;
else
goto <bb 4>;
<bb 4>:
return;
}
which later results in the loop getting optimized away. However
marking spinlock as volatile let the loop remain.
I originally thought this to be a problem . However after chatting
about it on IRC I wasn't sure if this was (un)defined behaviour. I
looked through the standard but was unable to figure out from the
prose , whether it stated some place that the object pointed to also
should also have the same type qualifiers as the pointer being used to
access this.
Thanks in advance
Ramana
--
Ramana Radhakrishnan
