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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r11-5820] tree-optimization/98117 - fix range set by vectorization on niter IVs Date: Mon, 7 Dec 2020 11:06:00 +0000 (GMT) [thread overview] Message-ID: <20201207110600.B9FB73857824@sourceware.org> (raw) https://gcc.gnu.org/g:cdcbef3c3310a14f2994982b44cb1f8e14c77232 commit r11-5820-gcdcbef3c3310a14f2994982b44cb1f8e14c77232 Author: Richard Biener <rguenther@suse.de> Date: Mon Dec 7 10:29:07 2020 +0100 tree-optimization/98117 - fix range set by vectorization on niter IVs This avoids the degenerate case of a TYPE_MAX_VALUE latch iteration count value causing wrong range info for the vector IV. There's still the case of VF == 1 where if we don't know whether we hit the above case we cannot emit a range. 2020-12-07 Richard Biener <rguenther@suse.de> PR tree-optimization/98117 * tree-vect-loop-manip.c (vect_gen_vector_loop_niters): Properly handle degenerate niter when setting the vector loop IV range. * gcc.dg/torture/pr98117.c: New testcase. Diff: --- gcc/testsuite/gcc.dg/torture/pr98117.c | 19 +++++++++++++++++++ gcc/tree-vect-loop-manip.c | 28 ++++++++++++++++++++++------ 2 files changed, 41 insertions(+), 6 deletions(-) diff --git a/gcc/testsuite/gcc.dg/torture/pr98117.c b/gcc/testsuite/gcc.dg/torture/pr98117.c new file mode 100644 index 00000000000..f2160257263 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr98117.c @@ -0,0 +1,19 @@ +/* { dg-do run } */ +/* { dg-additional-options "-fno-tree-scev-cprop" } */ + +unsigned char c; +void __attribute__((noipa)) +e() +{ + do + { + } + while (++c); +} +int main() +{ + e(); + if (c != 0) + __builtin_abort (); + return 0; +} diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c index 36179188f6d..2370b879b21 100644 --- a/gcc/tree-vect-loop-manip.c +++ b/gcc/tree-vect-loop-manip.c @@ -2034,13 +2034,29 @@ vect_gen_vector_loop_niters (loop_vec_info loop_vinfo, tree niters, niters_vector = force_gimple_operand (niters_vector, &stmts, true, var); gsi_insert_seq_on_edge_immediate (pe, stmts); /* Peeling algorithm guarantees that vector loop bound is at least ONE, - we set range information to make niters analyzer's life easier. */ + we set range information to make niters analyzer's life easier. + Note the number of latch iteration value can be TYPE_MAX_VALUE so + we have to represent the vector niter TYPE_MAX_VALUE + 1 >> log_vf. */ if (stmts != NULL && log_vf) - set_range_info (niters_vector, VR_RANGE, - wi::to_wide (build_int_cst (type, 1)), - wi::to_wide (fold_build2 (RSHIFT_EXPR, type, - TYPE_MAX_VALUE (type), - log_vf))); + { + if (niters_no_overflow) + set_range_info (niters_vector, VR_RANGE, + wi::one (TYPE_PRECISION (type)), + wi::rshift (wi::max_value (TYPE_PRECISION (type), + TYPE_SIGN (type)), + exact_log2 (const_vf), + TYPE_SIGN (type))); + /* For VF == 1 the vector IV might also overflow so we cannot + assert a minimum value of 1. */ + else if (const_vf > 1) + set_range_info (niters_vector, VR_RANGE, + wi::one (TYPE_PRECISION (type)), + wi::rshift (wi::max_value (TYPE_PRECISION (type), + TYPE_SIGN (type)) + - (const_vf - 1), + exact_log2 (const_vf), TYPE_SIGN (type)) + + 1); + } } *niters_vector_ptr = niters_vector; *step_vector_ptr = step_vector;
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