Sun Chan wrote:
> the wrap_around_unsafe flag is supposed to be used to guard that.
> Also, it is supposed to be turn off for O3, as I recall
> sun
>
I don't believe that LNO used that. Also, I would think the compiler
should be more conservative in allowing that "n" might be a small
positive number than in allowing that "n" might be close to 2^31.
Dror
> On Wed, Sep 22, 2010 at 4:57 AM, Dror Maydan <may...@tensilica.com> wrote:
>
>> We ran into the following bug.
>>
>> int a[1024];
>> void r(unsigned int n)
>> {
>> unsigned int i,j;
>> for (i=0; i<n; i++) {
>> for (j=0; j<n; j++) {
>> a[i]++;
>> }
>> }
>> }
>>
>>
>> At -O3, LNO outer unrolls the outer loop by setting the bound to
>> "i<n-u+1", creating an infinite loop whenever "n" is less than the
>> unroll factor. My memory is faded, but I thought it wasn't supposed to
>> do that for unsigned loops. From a quick scan of the code, I didn't
>> find anything that checks. Anyone have experience with this or a better
>> recollection than I do?
>>
>> Dror
>>
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