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| author | Richard Sandiford <richard.sandiford@linaro.org> | 2017-06-23 15:57:58 +0100 |
|---|---|---|
| committer | Richard Sandiford <richard.sandiford@linaro.org> | 2017-11-19 14:48:27 +0000 |
| commit | 51714d91a47c0324fe39251244e06a32e951f5ca (patch) | |
| tree | a6a8594a8ca5a338c9d3458e0abd08155439d8ab | |
| parent | 89052115d558e96460d77137b722f8c9780ba063 (diff) | |
| download | gcc-51714d91a47c0324fe39251244e06a32e951f5ca.tar.gz | |
Protect against min_profitable_iters going negative
We had:
if (vec_outside_cost <= 0)
min_profitable_iters = 0;
else
{
min_profitable_iters = ((vec_outside_cost - scalar_outside_cost)
* assumed_vf
- vec_inside_cost * peel_iters_prologue
- vec_inside_cost * peel_iters_epilogue)
/ ((scalar_single_iter_cost * assumed_vf)
- vec_inside_cost);
which can lead to negative min_profitable_iters when the *_outside_costs
are the same and peel_iters_epilogue is nonzero (e.g. if we're peeling
for gaps).
This is tested as part of the patch that adds support for fully-predicated
loops.
2017-11-08 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>
gcc/
* tree-vect-loop.c (vect_estimate_min_profitable_iters): Make sure
min_profitable_iters doesn't go negative.
| -rw-r--r-- | gcc/tree-vect-loop.c | 19 |
1 files changed, 10 insertions, 9 deletions
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c index ab222b85a3f..793c22ac61d 100644 --- a/gcc/tree-vect-loop.c +++ b/gcc/tree-vect-loop.c @@ -3651,23 +3651,24 @@ vect_estimate_min_profitable_iters (loop_vec_info loop_vinfo, if ((scalar_single_iter_cost * assumed_vf) > (int) vec_inside_cost) { - if (vec_outside_cost <= 0) + min_profitable_iters = ((vec_outside_cost - scalar_outside_cost) + * assumed_vf + - vec_inside_cost * peel_iters_prologue + - vec_inside_cost * peel_iters_epilogue); + + if (min_profitable_iters <= 0) min_profitable_iters = 0; else - { - min_profitable_iters = ((vec_outside_cost - scalar_outside_cost) - * assumed_vf - - vec_inside_cost * peel_iters_prologue - - vec_inside_cost * peel_iters_epilogue) - / ((scalar_single_iter_cost * assumed_vf) - - vec_inside_cost); + { + min_profitable_iters /= ((scalar_single_iter_cost * assumed_vf) + - vec_inside_cost); if ((scalar_single_iter_cost * assumed_vf * min_profitable_iters) <= (((int) vec_inside_cost * min_profitable_iters) + (((int) vec_outside_cost - scalar_outside_cost) * assumed_vf))) min_profitable_iters++; - } + } } /* vector version will never be profitable. */ else |