https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102756
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2021-10-15
Keywords| |missed-optimization
Summary|[12 Regression] Vectorizer |[12 Regression] Complete
|change creates poor code |unrolling is too senative
|for |to PRE;
|c-c++-common/torture/vector |c-c++-common/torture/vector
|-compare-2.c |-compare-2.c
Status|UNCONFIRMED |NEW
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
With -ftree-vectorize
size: 7-4, last_iteration: 7-4
Loop size: 7
Estimated size after unrolling: 8
_1 = VIEW_CONVERT_EXPR<int[4]>(r)[i_10];
With -fno-tree-vectorize
size: 7-4, last_iteration: 6-4
Loop size: 7
Estimated size after unrolling: 7
pretmp_2 = MEM[(vector(4) int *)&r][i_7];
Also -O2 -fno-tree-vectorize -fno-tree-pre produces the same as the -O2
-ftree-vectorize case.
------------------- CUT ----------------------------
Loop 1 iterates 3 times.
Loop 1 iterates at most 3 times.
Loop 1 likely iterates at most 3 times.
Estimating sizes for loop 1
BB: 3, after_exit: 0
size: 1 _1 = VIEW_CONVERT_EXPR<int[4]>(r)[i_10];
size: 2 if (_1 != -3)
BB: 7, after_exit: 1
BB: 5, after_exit: 0
size: 1 i_7 = i_10 + 1;
Induction variable computation will be folded away.
size: 1 ivtmp_9 = ivtmp_2 - 1;
Induction variable computation will be folded away.
size: 2 if (ivtmp_9 != 0)
Exit condition will be eliminated in peeled copies.
Exit condition will be eliminated in last copy.
Constant conditional.
size: 7-4, last_iteration: 7-4
Loop size: 7
Estimated size after unrolling: 8
Not unrolling loop 1: size would grow.
vs:
Estimating sizes for loop 1
BB: 3, after_exit: 0
size: 2 if (prephitmp_9 != -3)
BB: 6, after_exit: 1
size: 1 pretmp_2 = MEM[(vector(4) int *)&r][i_7];
BB: 5, after_exit: 0
size: 1 i_7 = i_10 + 1;
Induction variable computation will be folded away.
size: 1 ivtmp_11 = ivtmp_1 - 1;
Induction variable computation will be folded away.
size: 2 if (ivtmp_11 != 0)
Exit condition will be eliminated in peeled copies.
Exit condition will be eliminated in last copy.
Constant conditional.
size: 7-4, last_iteration: 6-4
Loop size: 7
Estimated size after unrolling: 7
PRE decides to do the load for MEM[(vector(4) int *)&r][0] which is why the
last iteration is 6-4 rather than 7-4.
