On Wed, Feb 11, 2015 at 9:23 AM, Bin.Cheng <amker.ch...@gmail.com> wrote: > On Tue, Feb 10, 2015 at 12:24 AM, Richard Biener > <richard.guent...@gmail.com> wrote: >> On February 9, 2015 11:09:49 AM CET, Bin Cheng <bin.ch...@arm.com> wrote: >> >> Did you extract a testcase for it? Note that the IV step itself may be >> expanded >> Too much. >> >> I >>>looked into the regression and thought it was because of passes after >>>IVOPT. >>>The IVOPT dump is at least not worse than the original version. >> >> But different I presume. So how did you figure it regressed? > The tree level dump is like, > > --- Without patch > +++ With patch > <bb 8>: > _618 = MAX_EXPR <n_105, 0>; > _619 = (integer(kind=8)) _618; > _629 = (unsigned long) _618; > > ...... > > <bb 37>: > _257 = _619 + 1; > _255 = (sizetype) _257; > _261 = _255 * 8; > _256 = (sizetype) _140; > - _1174 = (sizetype) _618; > + _1174 = (sizetype) _619; > _1175 = _256 + _1174; > _1176 = _1175 * 8; > _1177 = _148 + _1176; > ivtmp.3849_258 = (unsigned long) _1177; > _1179 = (unsigned int) _104; > > Previously, the computation of _1174 can be replaced by _629 in bb8 in > DOM2 pass, while it can't after patching. This is the only possible > regression that I can see on TREE level. There is another difference > but not regression on TREE. Seems real change happens on RTL pre with > different register uses in the input. I failed to go further or > extract a test case, it's just very volatile.
Well, I can see what is happening and indeed we shouldn't blame the patch for this. > With all of this, I guess this patch shouldn't be blamed for this. I > also wonder if the PR should be fixed in this way since the patch > definitely is a corner case. It might not fix the real issue (whatever that is), but not making IVOPTs (or tree-affines) life harder is very good (I believe I have seen this kind of issue as well). So I do think that the patch is fine. Just seen the known-to-work GCC 3.4 version so it's even a regression .... Thanks, Richard. > Thanks, > bin >> >> Thanks, >> Richard. >> >>>Bootstrap and test on x86_64 and AArch64, so is it OK? >>> >>>2015-02-09 Bin Cheng <bin.ch...@arm.com> >>> >>> PR tree-optimization/64705 >>> * tree-ssa-loop-niter.h (expand_simple_operations): New parameter. >>> * tree-ssa-loop-niter.c (expand_simple_operations): New parameter. >>> (tree_simplify_using_condition_1, refine_bounds_using_guard) >>> (number_of_iterations_exit): Pass new argument to >>> expand_simple_operations. >>> * tree-ssa-loop-ivopts.c (extract_single_var_from_expr): New. >>> (find_bivs, find_givs_in_stmt_scev): Pass new argument to >>> expand_simple_operations. Call extract_single_var_from_expr. >>> (difference_cannot_overflow_p): Pass new argument to >>> expand_simple_operations. >>> >>>gcc/testsuite/ChangeLog >>>2015-02-09 Bin Cheng <bin.ch...@arm.com> >>> >>> PR tree-optimization/64705 >>> * gcc.dg/tree-ssa/pr64705.c: New test. >> >>
