From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2136) id 75C613858426; Mon, 7 Nov 2022 19:59:33 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 75C613858426 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1667851184; bh=ti5jqls4Tn5lKlyhA9RnZSz7ROlAMMQnjd/HDw7bA74=; h=From:To:Subject:Date:From; b=o3Hwl8DPelW5jkb9i2cR2HhWYh3H7jTr/rog6XFM1rT183R7B6rjxLPsVNQ9Xi0I/ dmAo2VF4+rdVTQ2GVTtXVQfSU1QY6aaWr4ks5uKldGV2wrnQ6hcEHAhjKx+XZ04xVV X8+s26GMQIotIWzw/IAxi4EJkp0/I9mtP/T5aU3k= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Aldy Hernandez To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-3761] Improve multiplication by powers of 2 in range-ops. X-Act-Checkin: gcc X-Git-Author: Aldy Hernandez X-Git-Refname: refs/heads/master X-Git-Oldrev: 03ed4e57e3d46a61513b3d1ab1720997aec8cf71 X-Git-Newrev: a239a63f868e29e9276088e7c0fb00804c2903ba Message-Id: <20221107195944.75C613858426@sourceware.org> Date: Mon, 7 Nov 2022 19:59:33 +0000 (GMT) List-Id: https://gcc.gnu.org/g:a239a63f868e29e9276088e7c0fb00804c2903ba commit r13-3761-ga239a63f868e29e9276088e7c0fb00804c2903ba Author: Aldy Hernandez 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" } }