Hi,
On Thu, 5 May 2005, Daniel Berlin wrote:
> You can do it, but apparently restrict isn't as simple as "a and b are
> both restrict pointers and therefore can never alias", because that's
> not the actual definition of restrict. It says stuff about pointers
> "based on" restricted objects, etc.
On Wed, 2005-05-04 at 20:41 -0400, Diego Novillo wrote:
> On Wed, May 04, 2005 at 05:08:23PM -0700, James E Wilson wrote:
>
> > We can perhaps handle this well in the tree-aliasing code (if
> > it handled restrict at all), but it would be difficult to
> > handle this well in the RTL aliasing code.
On Wed, May 04, 2005 at 05:08:23PM -0700, James E Wilson wrote:
> We can perhaps handle this well in the tree-aliasing code (if
> it handled restrict at all), but it would be difficult to
> handle this well in the RTL aliasing code.
>
It doesn't. Mostly for similar reasons.
Perhaps we could be m
On Wed, 2005-05-04 at 16:24, Jeroen Dobbelaere wrote:
> I'm aware of that. The reason are asked for more clarity is that I
> think gcc should
> do better (as in the example I gave), but I want to be sure that this
> is still allowed
> by the standard.
Certainly gcc can and should do better, and th
On 5/4/05, James E Wilson wrote:
[..]
> The standard says "A translator is free to ignore any or all aliasing
> implications of restrict". So there is no conflict with the standard
> here. We are free to do as little optimization as we want, and in the
> case of a restricted char pointer, we do n
On Wed, 2005-05-04 at 14:27, Jeroen Dobbelaere wrote:
> Is this correct ?
I was only trying to explain how gcc works for the one example that you
posted. I was not trying to explain precise semantics of how restrict
works according to the ISO C standard, and my message should not be
construed as
On 5/4/05, James E Wilson <[EMAIL PROTECTED]> wrote:
[..]
> The optimization does not happen for this example because we apparently
> have no way to represent an alias set for a restricted char pointer.
> char * and void * are allowed to alias anything. That is alias set 0
> internally. A restric
Jeroen Dobbelaere wrote:
void test_2(unsigned long* __restrict__ bar, char* __restrict__ bas)
{
unsigned long tmp = *bar;
*bas = 0;
*bar = tmp;
}
The optimization in the first example happens in the postreload cse
pass, and is relying on RTL alias analysis info.
The optimization does not ha
Hi,
I have a question concerning '__restrict__' :
With gcc-4.0.0 (-O3 -fomit-frame-pointer, on i686), following piece of code :
void test_1(unsigned long* __restrict__ bar, unsigned long* __restrict__ bas)
{
unsigned long tmp = *bar;
*bas = 0;
*bar = tmp;
}
void test_2(unsigned long* __r
