Hi, Richard. I tried your suggestion which is applying your code and PR106019. It works for me now. Thank you so much. I will apply your suggestion on RVV GCC12.2 downstream (Because it has not been supported on upstream). I have another question: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99409 It seems that this issue occurs because GCC miss scalar-expansion optimization. I read the book 《Compiler Challenges for High-Performance Architectures》. There is a chapter: Chapter 5.3 Scalar Expansion. Is it a good idea to implement a new pass in GCC following the scalar expansion algorithm this book provided? Or you have another better option to fix this issue ? Thanks. juzhe.zhong@rivai.ai From: Richard Biener Date: 2022-09-22 16:48 To: juzhe.zhong@rivai.ai CC: gcc-patches Subject: Re: Re: [PATCH] DSE: Enhance dse with def-ref analysis On Thu, 22 Sep 2022, juzhe.zhong@rivai.ai wrote: > Does your local code exclude my codes? > I am using GCC12.2. When I delete all my codes and apply your codes only. > It fails to delete redundant stores and no auto-vecotorization of my RVV GCC in this test. > I am not sure whether I am on the same page with you. I applied my patch to GCC master where it handles the testcase from the PR in the first 042t.dse1 pass. I have not applied your patch. The patch needs an amendment to pass bootstrap, if (is_gimple_assign (use_stmt)) needs to be if (ref->ref && is_gimple_assign (use_stmt)) testing then also reveals XPASS: gcc.dg/vect/tsvc/vect-tsvc-s243.c -flto -ffat-lto-objects scan-tree-dump vect "vectorized 1 loops" XPASS: gcc.dg/vect/tsvc/vect-tsvc-s243.c scan-tree-dump vect "vectorized 1 loops" I guess that's expected. Indeed when applying the patch to the GCC 12 branch the case isn't optimized. I think it's probably the PR106019 fix missing, aka r13-1203-g038b077689bb53 Richard. > > > > juzhe.zhong@rivai.ai > > From: Richard Biener > Date: 2022-09-22 16:01 > To: juzhe.zhong@rivai.ai > Subject: Re: Re: [PATCH] DSE: Enhance dse with def-ref analysis > On Thu, 22 Sep 2022, juzhe.zhong@rivai.ai wrote: > > > I tried this solution you gave: > > >> else if (ref_maybe_used_by_stmt_p (use_stmt, ref)) > > >> { > > >> if (is_gimple_assign (use_stmt)) > > >> { > > >> data_reference_p dra, drb; > > >> dra = create_data_ref (NULL, NULL, ref->ref, stmt, > > >> false, false); > > >> drb = create_data_ref (NULL, NULL, > > >> gimple_assign_rhs1 (use_stmt), > > >> use_stmt, false, false); > > >> bool alias_p = dr_may_alias_p (dra, drb, NULL); > > >> free_data_ref (dra); > > >> free_data_ref (drb); > > >> if (!alias_p) > > >> { > > >> if (gimple_vdef (use_stmt)) > > >> defs.safe_push (use_stmt); > > >> continue; > > >> } > > >> } > > > > It still fails to delete the redundant store. The reason is when checking the redundant store. > > it didn't match the condtion: ref_maybe_used_by_stmt_p (use_stmt, ref). > > It does for me: > > Deleted dead store: a[i_18] = _5; > > ... > > : > _1 = b[i_18]; > _2 = c[i_18]; > _3 = d[i_18]; > _4 = _2 * _3; > _5 = _1 + _4; > _8 = e[i_18]; > _9 = _3 * _8; > _10 = _5 + _9; > b[i_18] = _10; > _12 = i_18 + 1; > _13 = a[_12]; > _15 = _3 * _13; > _16 = _10 + _15; > a[i_18] = _16; > > the other relevant function is stmt_kills_ref_p, that one does > handle a[i_18] vs. a[i_18] just fine. > > > Maybe we should first figure why it doesn't satisfy this situation? > > > > > > juzhe.zhong@rivai.ai > > > > From: Richard Biener > > Date: 2022-09-22 15:44 > > To: Ju-Zhe Zhong > > CC: gcc-patches; richard.sandiford > > Subject: Re: [PATCH] DSE: Enhance dse with def-ref analysis > > On Thu, 22 Sep 2022, Richard Biener wrote: > > > > > On Thu, 22 Sep 2022, juzhe.zhong@rivai.ai wrote: > > > > > > > From: Ju-Zhe Zhong > > > > > > > > This patch fix issue: PR 99407 > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99407 > > > > > > > > The enhancement implementation is simple: > > > > 1.Search gimple statement in program reverse order. > > > > 2.Queue the store statement which may be possible kill the def > > > > of previous store statement. > > > > 3.Perform dse_def_ref_analysis to remove stores will not kill > > > > any def. > > > > For example: > > > > a[i_18] = _5; > > > > ... > > > > foo (&a); > > > > a[i_18] = _7; > > > > > > > > a[i_18] = _7 is queued at the begining and will be removed > > > > in dse_def_ref_analysis. > > > > 4.Remove the store if the def is confirmed to be killed. > > > > > > But we already do the very same thing in dse_classify_store, I fail > > > to see why we need to have an alternate implementation? It also > > > seems to be quadratic in the size of a basic-block? > > > > > > The issue with dse_classify_store is that it relies on > > > ref_maybe_used_by_stmt_p but that doesn't handle > > > > > > a[i] = ..; > > > .. = a[i+1]; > > > > > > but when seeing a[_1] vs. a[_2] (two variable offsets), it gives > > > up, asserting may-aliasing. We do have infrastructure to catch > > > such cases with data reference analysis. If we want to catch > > > these cases we should use that instead. Given we have a > > > DSE/DCE pass pair right before loop optimizations we could even > > > move those inside of the loop pipeline and perform this more > > > expensive checks conditional on loop/scev availability. > > > > Oh, and when doing non-loop aware analysis we don't need SCEV. The > > following optimizes the testcase but as said I don't think we want > > to perform this for each of the DSE passes since it can be somewhat > > expensive, at least without doing more caching (we could keep a > > stmt -> data-ref hash-map and compute data-refs at most once for each > > statement, that would make it more acceptable). > > > > Richard. > > > > From 515b213e9d06c2bd36160e66728f57e48095bb84 Mon Sep 17 00:00:00 2001 > > From: Richard Biener > > Date: Thu, 22 Sep 2022 09:40:40 +0200 > > Subject: [PATCH] tree-optimization/99407 - DSE with data-ref analysis > > To: gcc-patches@gcc.gnu.org > > > > * tree-ssa-dse.c (dse_classify_store): Use data-ref analysis > > to disambiguate more uses. > > --- > > gcc/tree-ssa-dse.cc | 21 +++++++++++++++++++++ > > 1 file changed, 21 insertions(+) > > > > diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc > > index 34cfd1a8802..340a54f4105 100644 > > --- a/gcc/tree-ssa-dse.cc > > +++ b/gcc/tree-ssa-dse.cc > > @@ -45,6 +45,8 @@ along with GCC; see the file COPYING3. If not see > > #include "ipa-modref.h" > > #include "target.h" > > #include "tree-ssa-loop-niter.h" > > +#include "cfgloop.h" > > +#include "tree-data-ref.h" > > /* This file implements dead store elimination. > > @@ -1019,6 +1021,25 @@ dse_classify_store (ao_ref *ref, gimple *stmt, > > /* If the statement is a use the store is not dead. */ > > else if (ref_maybe_used_by_stmt_p (use_stmt, ref)) > > { > > + if (is_gimple_assign (use_stmt)) > > + { > > + data_reference_p dra, drb; > > + dra = create_data_ref (NULL, NULL, ref->ref, stmt, > > + false, false); > > + drb = create_data_ref (NULL, NULL, > > + gimple_assign_rhs1 (use_stmt), > > + use_stmt, false, false); > > + bool alias_p = dr_may_alias_p (dra, drb, NULL); > > + free_data_ref (dra); > > + free_data_ref (drb); > > + if (!alias_p) > > + { > > + if (gimple_vdef (use_stmt)) > > + defs.safe_push (use_stmt); > > + continue; > > + } > > + } > > + > > /* Handle common cases where we can easily build an ao_ref > > structure for USE_STMT and in doing so we find that the > > references hit non-live bytes and thus can be ignored. > > > > -- Richard Biener SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)