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. 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. 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. > >
