On Thu, Sep 4, 2014 at 10:59 AM, Bin Cheng <bin.ch...@arm.com> wrote: > Hi, > As reported by pr62631, case ivopts-lt-2.c is failed on sparc64. The root > cause is shiftadd_cost calculated on sparc64 is huge which prevents gcc from > choosing the wanted candidate. The problem with IVOPT is it always assumes > that shiftadd_cost is smaller than the normal cost, while it's not true in > this extreme case. This patch checks if the shiftadd_cost is smaller before > returning it. The patch also cleans code indent in context. > > One question is left here. > Why >100 cost is calculated for shiftadd on sparc64? In final assembly > code, the computation is implemented by separated shift and add > instructions. Probably sparc64 should return cost no larger than > cost(shift)+cost(add) in the first place?. > > Bootstrap and tested on x86_64/cortex-m3, the case is fixed on sparc64 now. > Is it OK?
So is the IVOPTs code just checking if the target returned sth > cost(shift) + cost(add)? Then I think we should fix the target instead. Richard. > Thanks, > bin > > > 2014-09-04 Bin Cheng <bin.ch...@arm.com> > > * tree-ssa-loop-ivopts.c (force_expr_to_var_cost): Return cost > calculated by get_shiftadd_cost only when it is smaller. Fix > code indent.
