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* [gcc(refs/vendors/redhat/heads/gcc-8-branch)] tree-optimization/98117 - fix range set by vectorization on niter IVs
@ 2021-05-14 14:54 Jakub Jelinek
0 siblings, 0 replies; only message in thread
From: Jakub Jelinek @ 2021-05-14 14:54 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:8633465e377d507fe86848781500de68bdd28f68
commit 8633465e377d507fe86848781500de68bdd28f68
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.
(cherry picked from commit 69894ce172412996c10c89838717980ede7c9003)
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 e82c1fe027e..8e41f5faf83 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -1967,13 +1967,29 @@ 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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