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From: Aldy Hernandez <aldyh@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-3217] [PR107195] Set range to zero when nonzero mask is 0. Date: Tue, 11 Oct 2022 08:31:55 +0000 (GMT) [thread overview] Message-ID: <20221011083155.1D1C0385735E@sourceware.org> (raw) https://gcc.gnu.org/g:c4d15dddf6b9eacb36f535807ad2ee364af46e04 commit r13-3217-gc4d15dddf6b9eacb36f535807ad2ee364af46e04 Author: Aldy Hernandez <aldyh@redhat.com> Date: Mon Oct 10 20:42:10 2022 +0200 [PR107195] Set range to zero when nonzero mask is 0. When solving 0 = _15 & 1, we calculate _15 as: [irange] int [-INF, -2][0, +INF] NONZERO 0xfffffffe The known value of _15 is [0, 1] NONZERO 0x1 which is intersected with the above, yielding: [0, 1] NONZERO 0x0 This eventually gets copied to a _Bool [0, 1] NONZERO 0x0. This is problematic because here we have a bool which is zero, but returns false for irange::zero_p, since the latter does not look at nonzero bits. This causes logical_combine to assume the range is not-zero, and all hell breaks loose. I think we should just normalize a nonzero mask of 0 to [0, 0] at creation, thus avoiding all this. PR tree-optimization/107195 gcc/ChangeLog: * value-range.cc (irange::set_range_from_nonzero_bits): Set range to [0,0] when nonzero mask is 0. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr107195-1.c: New test. * gcc.dg/tree-ssa/pr107195-2.c: New test. Diff: --- gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c | 15 +++++++++++++++ gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c | 16 ++++++++++++++++ gcc/value-range.cc | 5 +++++ 3 files changed, 36 insertions(+) diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c new file mode 100644 index 00000000000..a0c20dbd4b1 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-1.c @@ -0,0 +1,15 @@ +// { dg-do run } +// { dg-options "-O1 -fno-tree-ccp" } + +int a, b; +int main() { + int c = 0; + if (a) + c = 1; + c = 1 & (a && c) && b; + if (a) { + b = c; + __builtin_abort (); + } + return 0; +} diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c new file mode 100644 index 00000000000..d447c78bdd3 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr107195-2.c @@ -0,0 +1,16 @@ +// { dg-do run } +// { dg-options "-O1" } + +int a, b; +int main() { + int c = 0; + long d; + for (; b < 1; b++) { + (c && d) & 3 || a; + d = c; + c = -1; + if (d) + __builtin_abort(); + } + return 0; +} diff --git a/gcc/value-range.cc b/gcc/value-range.cc index a14f9bc4394..e07d2aa9a5b 100644 --- a/gcc/value-range.cc +++ b/gcc/value-range.cc @@ -2903,6 +2903,11 @@ irange::set_range_from_nonzero_bits () } return true; } + else if (popcount == 0) + { + set_zero (type ()); + return true; + } return false; }
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