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Re: Tree-SSA and POST_INC address mode inompatible in GCC4?
Hi,
> >> I believe that this is something new and is most likely fallout from
> >> diego's reworking of the tree to rtl converter.
> >>
> >> To fix this will require a round of copy propagation, most likely in
> >> concert with some induction variable detection, since the most
> >> profitable place for this will be in loops.
> >>
> >> I wonder if any of this effects the rtl level induction variable
> >> discovery?
> >>
> >
> > it should not (iv analysis is able to deal with this kind of ivs).
> >
> does the iv analysis canonize them in a way that we should perhaps
> consider moving the auto-inc detection after the iv analysis?
no, iv analysis does not change the program; also, since the code in
this particular example is not in any loop, iv analysis is somewhat
irrelevant for it.
Btw. I would have actually expected this code to be folded to
*a_3(D) = D.1543_2;
a_4 = a_3(D) + 1;
b_5 = b_1(D) + 1;
D.1543_6 = *b_5;
*a_4 = D.1543_6;
a_7 = a_3 + 2;
b_8 = b_1 + 2;
D.1543_9 = *b_8;
*a_7 = D.1543_9;
a_10 = a_3 + 3;
b_11 = b_1 + 3;
D.1543_12 = *b_11;
*a_10 = D.1543_12;
a_13 = a_3 + 4;
b_14 = b_1 + 4;
D.1543_15 = *b_14;
*a_13 = D.1543_15;
etc.; I am fairly sure we used to do this.
Zdenek