public inbox for gcc-cvs@sourceware.org help / color / mirror / Atom feed
From: Aldy Hernandez <aldyh@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-3761] Improve multiplication by powers of 2 in range-ops. Date: Mon, 7 Nov 2022 19:59:33 +0000 (GMT) [thread overview] Message-ID: <20221107195944.75C613858426@sourceware.org> (raw) https://gcc.gnu.org/g:a239a63f868e29e9276088e7c0fb00804c2903ba commit r13-3761-ga239a63f868e29e9276088e7c0fb00804c2903ba Author: Aldy Hernandez <aldyh@redhat.com> Date: Fri Nov 4 22:24:42 2022 +0100 Improve multiplication by powers of 2 in range-ops. For unsigned numbers, multiplication by X, where X is a power of 2 is [0,0][X,+INF]. This patch causes a regression to g++.dg/pr71488.C where -Wstringop-overflow gets the same IL as before, but better ranges cause it to issue a bogus warning. I will create a PR with some notes. No discernible changes in performance. Tested on x86-64 Linux. PR tree-optimization/55157 gcc/ChangeLog: * range-op.cc (operator_mult::wi_fold): Optimize multiplications by powers of 2. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr55157.c: New test. Diff: --- gcc/range-op.cc | 16 ++++++++++++++-- gcc/testsuite/gcc.dg/tree-ssa/pr55157.c | 19 +++++++++++++++++++ 2 files changed, 33 insertions(+), 2 deletions(-) diff --git a/gcc/range-op.cc b/gcc/range-op.cc index 2b5db0cac85..a13e88840a6 100644 --- a/gcc/range-op.cc +++ b/gcc/range-op.cc @@ -1911,8 +1911,20 @@ operator_mult::wi_fold (irange &r, tree type, // diff = max - min prod2 = prod3 - prod0; if (wi::geu_p (prod2, sizem1)) - // The range covers all values. - r.set_varying (type); + { + // Multiplying by X, where X is a power of 2 is [0,0][X,+INF]. + if (TYPE_UNSIGNED (type) && rh_lb == rh_ub + && wi::exact_log2 (rh_lb) != -1 && prec > 1) + { + r.set (type, rh_lb, wi::max_value (prec, sign)); + int_range<2> zero; + zero.set_zero (type); + r.union_ (zero); + } + else + // The range covers all values. + r.set_varying (type); + } else { wide_int new_lb = wide_int::from (prod0, prec, sign); diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr55157.c b/gcc/testsuite/gcc.dg/tree-ssa/pr55157.c new file mode 100644 index 00000000000..bbdda45bd64 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr55157.c @@ -0,0 +1,19 @@ +// { dg-do compile } +// { dg-options "-O2 -fdump-tree-evrp" } + +void gg(void); +int f(unsigned t) +{ + unsigned g = t*16; + if (g==0) return 1; + gg(); + gg(); + gg(); + gg(); + gg(); + gg(); + if (g<=4) return 1; + return 0; +} + +// { dg-final { scan-tree-dump-times " if " 1 "evrp" } }
reply other threads:[~2022-11-07 19:59 UTC|newest] Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20221107195944.75C613858426@sourceware.org \ --to=aldyh@gcc.gnu.org \ --cc=gcc-cvs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).