On Mon, Jun 1, 2015 at 4:00 PM, Richard Biener <richard.guent...@gmail.com> wrote: > On Sat, May 30, 2015 at 7:47 AM, Jeff Law <l...@redhat.com> wrote: >> On 05/19/2015 10:12 AM, Aditya K wrote: >>> >>> w.r.t. the PR48052, here is the patch which finds out if scev would wrap >>> or not. >>> The patch symbolically evaluates if valid_niter>= loop->nb_iterations is >>> true. In that case the scev would not wrap (??). >>> Currently, we only look for two special 'patterns', which are sufficient >>> to analyze the simple test cases. >>> >>> valid_niter = ~s (= UNIT_MAX - s) >>> We have to prove that valid_niter>= loop->nb_iterations >>> >>> Pattern1 loop->nb_iterations: s>= e ? s - e : 0 >>> Pattern2 loop->nb_iterations: (e - s) -1 >>> >>> In the first case we prove that valid_niter>= loop->nb_iterations in both >>> the cases i.e., when s>=e and when not. >>> In the second case we prove valid_niter>= loop->nb_iterations, by simple >>> analysis that UINT_MAX>= e is true in all cases. >>> >>> I haven't tested this patch completely. I'm looking for feedback and any >>> scope for improvement. >>> >>> >>> hth, >>> -Aditya >>> >>> >>> >>> Vectorize loops which has typecast. >>> >>> 2015-05-19 hiraditya <hiradi...@msn.com> >>> >>> * gcc.dg/vect/pr48052.c: New test. >>> >>> gcc/ChangeLog: >>> >>> 2015-05-19 hiraditya <hiradi...@msn.com> >>> >>> * tree-ssa-loop-niter.c (fold_binary_cond_p): Fold a conditional >>> operation when additional constraints are >>> available. >>> (fold_binary_minus_p): Fold a subtraction operations of the form >>> (A - B -1) when additional constraints are >>> available. >>> (scev_probably_wraps_p): Use the above two functions to find >>> whether valid_niter>= loop->nb_iterations. >> >> Is any of this work still useful if Bin Cheng's work on improving overflow >> detection for scev goes forward? I certainly got the impression that Bin's >> work would solve 48052 and others. > > Bin is probably the one to answer this. His patches are still on my list > of patches to review... Richard, you have already approved the first one. The second one is at https://gcc.gnu.org/ml/gcc-patches/2015-05/msg02317.html . You may need to decide if it is as expected.
Yes, PRs like 62173, 52563 and 48052 will be fixed with these two patches. Thanks, bin > > Richard. > >> Jeff >>
