Opening bug report per Zdeneck's request, snippets of email exchange follows:
=========
void f1 (void * coefPtr, double * dd)
{
int i,j;
/* Cast of "coefPtr" results in poor code for this loop (missed strength
reduction). */
for (i = 0; i < 16; i++) {
*(((double *) coefPtr) + i) = +0.0;
}
for (j = 0; j < 16; j++) {
*(dd + j) = +0.0;
}
}
=========
> this seems to be a problem with the cost function:
>
> Cost of strength reduction of the access =
> Cost for incrementing the new induction variable: 8
> Cost for increased register pressure: 4
> Cost for the memory reference: 1
>
> Cost for expressing the access using i =
> Cost for multiplication by 8: 12
> Cost for the memory reference: 1 (addition of the result of
> multiplications takes place in the address).
>
> The result is that it is not worthwhile to perform strength reduction.
> I will try to do something with the code that estimates cost of memory
> references, since it is quite wrong here.
could you please create a bugreport for this? The things are a bit more
complicated than what I expected; there is actually no way how the
target could let ivopts know that DFmode address for (reg + reg) is more
expensive than just reg, in the current state.
--
Summary: Missed ivopts opportunity
Product: gcc
Version: 4.0.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pthaugen at us dot ibm dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: powerpc64-linux
GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18768
