On Wed, Feb 10, 2016 at 12:34 PM, Bin Cheng <bin.ch...@arm.com> wrote: > Hi, > This is another way to fix PR68021, and I think it's the least intrusive way. > The issue is triggered in a special case in which cand is a original biv, > and use denotes the value of the biv itself. In this case, the use is added > specifically for the original biv, as a result, get_computation_aff isn't > called for the <cand, use> pair before rewriting the use. It is possible > that constant_multiple_of/operand_equal_q could fail because of inconsistent > fold behavior. The fold behavior is fully described in PR68021. > This patch fixes IVOPT part of issue by setting ratio to 1, because it is > known that the use has the value of the biv cand. > > Bootstrap and test on x86_64 and aarch64. Is it OK if no failures?
Ok, but please add a comment why we have this special-casing instead of relying on constant_multiple_of. Thanks, Richard. > Thanks, > bin > > 2016-02-09 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/68021 > * tree-ssa-loop-ivopts.c (get_computation_aff): Set ratio to 1 if > when computing the value of biv cand by itself. > > gcc/testsuite/ChangeLog > 2016-02-09 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/68021 > * gcc.dg/tree-ssa/pr68021.c: New test.
