| Message ID | AANLkTilkMtVXw_Pfmx272I8tAVJq6adGYaIKYuzd62r0@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Jun 8, 2010 at 16:23, Sebastian Pop <sebpop@gmail.com> wrote: > On Tue, Jun 8, 2010 at 14:11, Sebastian Pop <sebpop@gmail.com> wrote: >> Hi, >> >> I remarked that in add_conditions_to_domain, we are adding the exit >> condition of a loop to the basic blocks following the loop. >> Why do we need to do this? >> >> The example I am looking at is a bit more complicated than this, >> but here is an abstraction that shows the problem: >> >> loop >> bb0: >> i_0 = phi (0, i_1) >> i_1 = i_0 + 1 >> if (i_0 < 1000) >> goto bb1 >> else >> goto bb2 >> >> bb1: >> goto bb0 >> end_loop >> >> bb2: >> S; >> >> We want to add the condition "i_0 >= 1000" to the domain of bb2, and >> this fails in my case as the scev analysis is not able to compute the >> overall effect of the inner loop on i_0. In the end I wrote a patch >> that makes scev return the right answer, and not surprisingly, in the >> simple example above, we insert a useless constraint: 1000 >= 1000. > > So here is that other patch that makes the instantiation of the SCEVs > call compute_overall_effect_of_inner_loop when the instantiation > should happen in an outer loop than where the SSA_NAME was defined. > > Regstrap in progress on amd64-linux. Ok for trunk? Passed regstrap.
On Tue, 8 Jun 2010, Sebastian Pop wrote: > On Tue, Jun 8, 2010 at 16:23, Sebastian Pop <sebpop@gmail.com> wrote: > > On Tue, Jun 8, 2010 at 14:11, Sebastian Pop <sebpop@gmail.com> wrote: > >> Hi, > >> > >> I remarked that in add_conditions_to_domain, we are adding the exit > >> condition of a loop to the basic blocks following the loop. > >> Why do we need to do this? > >> > >> The example I am looking at is a bit more complicated than this, > >> but here is an abstraction that shows the problem: > >> > >> loop > >> bb0: > >> i_0 = phi (0, i_1) > >> i_1 = i_0 + 1 > >> if (i_0 < 1000) > >> goto bb1 > >> else > >> goto bb2 > >> > >> bb1: > >> goto bb0 > >> end_loop > >> > >> bb2: > >> S; > >> > >> We want to add the condition "i_0 >= 1000" to the domain of bb2, and > >> this fails in my case as the scev analysis is not able to compute the > >> overall effect of the inner loop on i_0. In the end I wrote a patch > >> that makes scev return the right answer, and not surprisingly, in the > >> simple example above, we insert a useless constraint: 1000 >= 1000. > > > > So here is that other patch that makes the instantiation of the SCEVs > > call compute_overall_effect_of_inner_loop when the instantiation > > should happen in an outer loop than where the SSA_NAME was defined. > > > > Regstrap in progress on amd64-linux. Ok for trunk? > > Passed regstrap. Ok. Thanks, Richard.
On Wed, Jun 9, 2010 at 04:58, Richard Guenther <rguenther@suse.de> wrote: > On Tue, 8 Jun 2010, Sebastian Pop wrote: > >> On Tue, Jun 8, 2010 at 16:23, Sebastian Pop <sebpop@gmail.com> wrote: >> > On Tue, Jun 8, 2010 at 14:11, Sebastian Pop <sebpop@gmail.com> wrote: >> >> Hi, >> >> >> >> I remarked that in add_conditions_to_domain, we are adding the exit >> >> condition of a loop to the basic blocks following the loop. >> >> Why do we need to do this? >> >> >> >> The example I am looking at is a bit more complicated than this, >> >> but here is an abstraction that shows the problem: >> >> >> >> loop >> >> bb0: >> >> i_0 = phi (0, i_1) >> >> i_1 = i_0 + 1 >> >> if (i_0 < 1000) >> >> goto bb1 >> >> else >> >> goto bb2 >> >> >> >> bb1: >> >> goto bb0 >> >> end_loop >> >> >> >> bb2: >> >> S; >> >> >> >> We want to add the condition "i_0 >= 1000" to the domain of bb2, and >> >> this fails in my case as the scev analysis is not able to compute the >> >> overall effect of the inner loop on i_0. In the end I wrote a patch >> >> that makes scev return the right answer, and not surprisingly, in the >> >> simple example above, we insert a useless constraint: 1000 >= 1000. >> > >> > So here is that other patch that makes the instantiation of the SCEVs >> > call compute_overall_effect_of_inner_loop when the instantiation >> > should happen in an outer loop than where the SSA_NAME was defined. >> > >> > Regstrap in progress on amd64-linux. Ok for trunk? >> >> Passed regstrap. > > Ok. > Committed on trunk r160510.
From c7a2e1b80c1e1d3c1eb32000b6a70ce4c4f75ed8 Mon Sep 17 00:00:00 2001 From: Sebastian Pop <sebpop@gmail.com> Date: Tue, 8 Jun 2010 13:21:56 -0500 Subject: [PATCH] Call compute_overall_effect_of_inner_loop from instantiate_scev_name. * tree-scalar-evolution.c (instantiate_scev_name): Do not fail the scev analysis when the variable is not used outside the loop in a close phi node: call compute_overall_effect_of_inner_loop. --- gcc/tree-scalar-evolution.c | 16 +++++++++++++--- 1 files changed, 13 insertions(+), 3 deletions(-) diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c index bf564d8..5dce6af 100644 --- a/gcc/tree-scalar-evolution.c +++ b/gcc/tree-scalar-evolution.c @@ -2172,9 +2172,19 @@ instantiate_scev_name (basic_block instantiate_below, else res = chrec; - if (res == NULL_TREE - || !dominated_by_p (CDI_DOMINATORS, instantiate_below, - gimple_bb (SSA_NAME_DEF_STMT (res)))) + /* When ther is no loop_closed_phi_def, it means that the + variable is not used after the loop: try to still compute the + value of the variable when exiting the loop. */ + if (res == NULL_TREE) + { + loop_p loop = loop_containing_stmt (SSA_NAME_DEF_STMT (chrec)); + res = analyze_scalar_evolution (loop, chrec); + res = compute_overall_effect_of_inner_loop (loop, res); + res = instantiate_scev_r (instantiate_below, evolution_loop, res, + fold_conversions, cache, size_expr); + } + else if (!dominated_by_p (CDI_DOMINATORS, instantiate_below, + gimple_bb (SSA_NAME_DEF_STMT (res)))) res = chrec_dont_know; } -- 1.7.0.4