From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1666) id 9E82D385800B; Mon, 24 Jan 2022 12:15:30 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9E82D385800B MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Richard Biener To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-6844] tree-optimization/102131 - fix niter analysis wrt overflow X-Act-Checkin: gcc X-Git-Author: Richard Biener X-Git-Refname: refs/heads/master X-Git-Oldrev: 2755037e40aa3549b38f6d080108e26fb5cb677b X-Git-Newrev: f1af8528d34418bc874ae9d993ee0dc3559972d2 Message-Id: <20220124121530.9E82D385800B@sourceware.org> Date: Mon, 24 Jan 2022 12:15:30 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 24 Jan 2022 12:15:30 -0000 https://gcc.gnu.org/g:f1af8528d34418bc874ae9d993ee0dc3559972d2 commit r12-6844-gf1af8528d34418bc874ae9d993ee0dc3559972d2 Author: Richard Biener Date: Mon Jan 24 11:50:06 2022 +0100 tree-optimization/102131 - fix niter analysis wrt overflow This fixes the overflow issues seen with analyzing BASE0 + STEP0 cmp BASE1 + STEP1 as BASE0 + STEP0 - STEP1 cmp BASE1 by following the logic we have when simplifying comparisons. 2022-01-24 Richard Biener Jiufu Guo PR tree-optimization/100740 PR tree-optimization/101508 PR tree-optimization/101972 PR tree-optimization/102131 * tree-ssa-loop-niter.cc (number_of_iterations_cond): Properly constrain BASE0 + STEP0 cmp BASE1 + STEP1 to BASE0 + STEP0 - STEP1 cmp BASE1 transform. * gcc.dg/torture/pr100740.c: New testcase. * gcc.dg/torture/pr101508.c: Likewise. * gcc.dg/torture/pr101972.c: Likewise. * gcc.dg/torture/pr102131-1.c: Likewise. * gcc.dg/torture/pr102131-2.c: Likewise. * gcc.dg/torture/pr102131-3.c: Likewise. * gcc.dg/torture/pr102131-4.c: Likewise. Diff: --- gcc/testsuite/gcc.dg/torture/pr100740.c | 12 ++++++++++ gcc/testsuite/gcc.dg/torture/pr101508.c | 13 +++++++++++ gcc/testsuite/gcc.dg/torture/pr101972.c | 39 +++++++++++++++++++++++++++++++ gcc/testsuite/gcc.dg/torture/pr102131-1.c | 16 +++++++++++++ gcc/testsuite/gcc.dg/torture/pr102131-2.c | 15 ++++++++++++ gcc/testsuite/gcc.dg/torture/pr102131-3.c | 11 +++++++++ gcc/testsuite/gcc.dg/torture/pr102131-4.c | 15 ++++++++++++ gcc/tree-ssa-loop-niter.cc | 32 +++++++++++++++++-------- 8 files changed, 143 insertions(+), 10 deletions(-) diff --git a/gcc/testsuite/gcc.dg/torture/pr100740.c b/gcc/testsuite/gcc.dg/torture/pr100740.c new file mode 100644 index 00000000000..a85855ebe18 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr100740.c @@ -0,0 +1,12 @@ +/* { dg-do run } */ + +unsigned a, b; +int main() +{ + unsigned c = 0; + for (a = 0; a < 2; a++) + for (b = 0; b < 2; b++) + if (++c < a) + __builtin_abort (); + return 0; +} diff --git a/gcc/testsuite/gcc.dg/torture/pr101508.c b/gcc/testsuite/gcc.dg/torture/pr101508.c new file mode 100644 index 00000000000..e1cb2645a31 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr101508.c @@ -0,0 +1,13 @@ +/* { dg-do run } */ + +int +main () +{ + unsigned i; + for (i = 0; i < 3; ++i) + { + if (i > i * 2) + __builtin_abort (); + } + return 0; +} diff --git a/gcc/testsuite/gcc.dg/torture/pr101972.c b/gcc/testsuite/gcc.dg/torture/pr101972.c new file mode 100644 index 00000000000..3adb4828ea5 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr101972.c @@ -0,0 +1,39 @@ +/* { dg-do run } */ +/* { dg-require-effective-target int32plus } */ + +int a, b, c, d, f; +static short e = 63891; +char g = 30; +unsigned h(int i, int j) { return i << j; } +int *l(int *); +void m() +{ + a = 0; + for (; a >= 0; a--) + { + int *k = &b; + *k = e < 0; + } + c = b; + l(&c); +} +int *l(int *i) +{ + d = 2; + for (; d <= 6; d++) + { + if (h(d, *i) <= d) + ; + else + continue; + g = 0; + return &f; + } + return (void *)0; +} +int main() +{ + m(); + if (g != 30) + __builtin_abort (); +} diff --git a/gcc/testsuite/gcc.dg/torture/pr102131-1.c b/gcc/testsuite/gcc.dg/torture/pr102131-1.c new file mode 100644 index 00000000000..5ff576d8634 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr102131-1.c @@ -0,0 +1,16 @@ +/* { dg-do run } */ + +int a; +int main() +{ + unsigned b = 0; + int c = 1; + for (; b < 3; b++) + { + while (c < b) + __builtin_abort (); + for (a = 0; a < 3; a++) + c++; + } + return 0; +} diff --git a/gcc/testsuite/gcc.dg/torture/pr102131-2.c b/gcc/testsuite/gcc.dg/torture/pr102131-2.c new file mode 100644 index 00000000000..830c72c23d9 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr102131-2.c @@ -0,0 +1,15 @@ +/* { dg-do run } */ + +int a; +int main() +{ + unsigned b = 0; + int c = 1; + for (;b < 3; b++) + { + if (c < b) + __builtin_abort (); + c+=3; + } + return 0; +} diff --git a/gcc/testsuite/gcc.dg/torture/pr102131-3.c b/gcc/testsuite/gcc.dg/torture/pr102131-3.c new file mode 100644 index 00000000000..aed10c973e6 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr102131-3.c @@ -0,0 +1,11 @@ +/* { dg-do run } */ + +int a; +int main() +{ + unsigned b = 0; + for (a = 2; a < 8; a += 2) + if (++b > a) + __builtin_abort(); + return 0; +} diff --git a/gcc/testsuite/gcc.dg/torture/pr102131-4.c b/gcc/testsuite/gcc.dg/torture/pr102131-4.c new file mode 100644 index 00000000000..c63c08b2137 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr102131-4.c @@ -0,0 +1,15 @@ +/* { dg-do run } */ +/* { dg-require-effective-target int32plus } */ + +unsigned a; +int main() +{ + unsigned b = 1; + for (; b < 4; b++) { + a = (a ^ 2000000000) * -b; + if (b > a) + __builtin_abort (); + a = 3000000000; + } + return 0; +} diff --git a/gcc/tree-ssa-loop-niter.cc b/gcc/tree-ssa-loop-niter.cc index 21cc257c91b..04c209561d8 100644 --- a/gcc/tree-ssa-loop-niter.cc +++ b/gcc/tree-ssa-loop-niter.cc @@ -1894,7 +1894,8 @@ number_of_iterations_cond (class loop *loop, provided that either below condition is satisfied: a) the test is NE_EXPR; - b) iv0.step - iv1.step is integer and iv0/iv1 don't overflow. + b) iv0 and iv1 do not overflow and iv0.step - iv1.step is of + the same sign and of less or equal magnitude than iv0.step This rarely occurs in practice, but it is simple enough to manage. */ if (!integer_zerop (iv0->step) && !integer_zerop (iv1->step)) @@ -1903,17 +1904,28 @@ number_of_iterations_cond (class loop *loop, tree step = fold_binary_to_constant (MINUS_EXPR, step_type, iv0->step, iv1->step); - /* No need to check sign of the new step since below code takes care - of this well. */ - if (code != NE_EXPR - && (TREE_CODE (step) != INTEGER_CST - || !iv0->no_overflow || !iv1->no_overflow)) - return false; + /* For code other than NE_EXPR we have to ensure moving the evolution + of IV1 to that of IV0 does not introduce overflow. */ + if (TREE_CODE (step) != INTEGER_CST + || !iv0->no_overflow || !iv1->no_overflow) + { + if (code != NE_EXPR) + return false; + iv0->no_overflow = false; + } + /* If the new step of IV0 has changed sign or is of greater + magnitude then we do not know whether IV0 does overflow + and thus the transform is not valid for code other than NE_EXPR */ + else if (tree_int_cst_sign_bit (step) != tree_int_cst_sign_bit (iv0->step) + || wi::gtu_p (wi::abs (wi::to_widest (step)), + wi::abs (wi::to_widest (iv0->step)))) + { + if (code != NE_EXPR) + return false; + iv0->no_overflow = false; + } iv0->step = step; - if (!POINTER_TYPE_P (type)) - iv0->no_overflow = false; - iv1->step = build_int_cst (step_type, 0); iv1->no_overflow = true; }