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From: Andrew Macleod <amacleod@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-2636] Change integral divide by zero to produce UNDEFINED. Date: Fri, 30 Jul 2021 19:12:12 +0000 (GMT) [thread overview] Message-ID: <20210730191212.A9ED539730C4@sourceware.org> (raw) https://gcc.gnu.org/g:ebbcdd7fae1f802763850e4afedfdfa09cf10e1a commit r12-2636-gebbcdd7fae1f802763850e4afedfdfa09cf10e1a Author: Andrew MacLeod <amacleod@redhat.com> Date: Wed Jul 28 13:14:22 2021 -0400 Change integral divide by zero to produce UNDEFINED. Instead of VARYING, we can get better results by treating divide by zero as producing an undefined result. gcc/ * range-op.cc (operator_div::wi_fold): Return UNDEFINED for [0, 0] divisor. gcc/testsuite/ * gcc.dg/tree-ssa/pr61839_2.c: Adjust. Diff: --- gcc/range-op.cc | 9 +-------- gcc/testsuite/gcc.dg/tree-ssa/pr61839_2.c | 3 +-- 2 files changed, 2 insertions(+), 10 deletions(-) diff --git a/gcc/range-op.cc b/gcc/range-op.cc index b1fb25c77f8..69228882930 100644 --- a/gcc/range-op.cc +++ b/gcc/range-op.cc @@ -1785,13 +1785,6 @@ operator_div::wi_fold (irange &r, tree type, const wide_int &lh_lb, const wide_int &lh_ub, const wide_int &rh_lb, const wide_int &rh_ub) const { - // If we know we will divide by zero... - if (rh_lb == 0 && rh_ub == 0) - { - r.set_varying (type); - return; - } - const wide_int dividend_min = lh_lb; const wide_int dividend_max = lh_ub; const wide_int divisor_min = rh_lb; @@ -1818,7 +1811,7 @@ operator_div::wi_fold (irange &r, tree type, // If we're definitely dividing by zero, there's nothing to do. if (wi_zero_p (type, divisor_min, divisor_max)) { - r.set_varying (type); + r.set_undefined (); return; } diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr61839_2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr61839_2.c index cfec54de991..f1b8feb4e9d 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/pr61839_2.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr61839_2.c @@ -45,9 +45,8 @@ int bar2 () return 0; } - /* Dont optimize 972195717 / 0 in function foo. */ -/* { dg-final { scan-tree-dump-times "972195717 / " 1 "evrp" } } */ +/* { dg-final { scan-tree-dump-times "972195717 / " 0 "evrp" } } */ /* Dont optimize 972195717 % 0 in function bar. */ /* { dg-final { scan-tree-dump-times "972195717 % " 1 "evrp" } } */ /* May optimize in function bar2, but EVRP doesn't perform this yet. */
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