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vect: Move suggested_unroll_factor applying [PR105940]

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As PR105940 shown, when rs6000 port tries to assign
m_suggested_unroll_factor by 4 or so, there will be ICE on:

  exact_div (LOOP_VINFO_VECT_FACTOR (loop_vinfo),
             loop_vinfo->suggested_unroll_factor);

In function vect_analyze_loop_2, the current place of
suggested_unroll_factor applying can't guarantee it's
applied for all cases.  As the case shows, vectorizer
could retry with SLP forced off, the vf is reset by
saved_vectorization_factor which isn't applied with
suggested_unroll_factor before.  It means it can end
up with one vf which neglects suggested_unroll_factor.
I think it's off design, we should move the applying
of suggested_unroll_factor after start_over.

	PR tree-optimization/105940

gcc/ChangeLog:

	* tree-vect-loop.cc (vect_analyze_loop_2): Move the place of
	applying suggested_unroll_factor after start_over.
This commit is contained in:
Kewen Lin 2022-06-14 00:57:01 -05:00
parent 077438933c
commit f907cf4c07
1 changed files with 3 additions and 3 deletions
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6
gcc/tree-vect-loop.cc
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@ -2388,15 +2388,15 @@ vect_analyze_loop_2 (loop_vec_info loop_vinfo, bool &fatal,
set of rgroups. */
gcc_assert (LOOP_VINFO_MASKS (loop_vinfo).is_empty ());
/* This is the point where we can re-start analysis with SLP forced off. */
start_over:
/* Apply the suggested unrolling factor, this was determined by the backend
during finish_cost the first time we ran the analyzis for this
vector mode. */
if (loop_vinfo->suggested_unroll_factor > 1)
LOOP_VINFO_VECT_FACTOR (loop_vinfo) *= loop_vinfo->suggested_unroll_factor;
/* This is the point where we can re-start analysis with SLP forced off. */
start_over:
/* Now the vectorization factor is final. */
poly_uint64 vectorization_factor = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
gcc_assert (known_ne (vectorization_factor, 0U));