On Tue, Mar 28, 2017 at 2:01 PM, Bin Cheng <bin.ch...@arm.com> wrote: > Hi, > This patch is to fix PR80153. As analyzed in the PR, root cause is > tree_affine lacks > ability differentiating (unsigned)(ptr + offset) and (unsigned)ptr + > (unsigned)offset, > even worse, it always returns the former expression in aff_combination_tree, > which > is wrong if the original expression has the latter form. The patch resolves > the issue > by always returning the latter form expression, i.e, always trying to > generate folded > expression. Also as analyzed in comment, I think this change won't result in > substantial > code gen difference. > I also need to adjust get_computation_aff for test case > gcc.dg/tree-ssa/reassoc-19.c. > Well, I think the changed behavior is correct, but for case the original > pointer candidate > is chosen, it should be unnecessary to compute in uutype. Also this > adjustment only > generates (unsigned)(pointer + offset) which is generated by tree-affine.c. > Bootstrap and test on x86_64 and AArch64. Is it OK?
Hmm. What is the desired goal? To have all elts added have comb->type as type? Then the type passed to add_elt_to_tree is redundant with comb->type. It looks like it is always passed comb->type now. ISTR from past work in this area that it was important for pointer combinations to allow both pointer and sizetype elts at least. Your change is incomplete I think, for the scale == -1 and POINTER_TYPE_P case elt is sizetype now, not of pointer type. As said above, we are trying to maintain both pointer and sizetype elts with like: if (scale == 1) { if (!expr) { if (POINTER_TYPE_P (TREE_TYPE (elt))) return elt; else return fold_convert (type1, elt); } where your earilier fold to type would result in not all cases handled the same (depending whether scale was -1 for example). Thus - shouldn't we simply drop the type argument (or rather the comb one? that wide_int_ext_for_comb looks weird given we get a widest_int as input and all the other wide_int_ext_for_comb calls around). And unconditionally convert to type, simplifying the rest of the code? Richard. > 2017-03-27 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/80153 > * tree-affine.c (add_elt_to_tree): Convert to type as required > by function's parameter. > * tree-ssa-loop-ivopts.c (alloc_iv): Pass in consistent types. > (get_computation_aff): Use utype directly for original candidate. > > gcc/testsuite/ChangeLog > 2017-03-27 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/80153 > * gcc.c-torture/execute/pr80153.c: New.