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tree-optimization/100778 - avoid cross-BB vectorization of trapping op

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This avoids vectorizing a possibly trapping operation when lanes
are handled in different BBs.  I spotted this when working on the
originally reported issue in PR100778.

2021-05-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/100778
	* tree-vect-slp.c (vect_build_slp_tree_1): Prevent possibly
	trapping ops in different BBs.

	* gcc.dg/vect/bb-slp-pr100778-1.c: New testcase.
This commit is contained in:
Richard Biener 2021-05-28 14:26:06 +02:00
parent f838e3ccf8
commit f7a07f5a5d
2 changed files with 20 additions and 2 deletions
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18
gcc/testsuite/gcc.dg/vect/bb-slp-pr100778-1.c Normal file
View file

@ -0,0 +1,18 @@
/* { dg-do compile } */
/* { dg-require-effective-target vect_double } */
double foo (int x, double *p)
{
double res = p[0] + p[1];
double tem = p[0] / x;
if (x)
{
p[0] = tem;
p[1] /= x;
}
return res + tem;
}
/* We may not SLP vectorize the FP division because it can trap and it
is distributed between two basic-blocks. */
/* { dg-final { scan-tree-dump "Build SLP failed: different BB for PHI or possibly trapping operation in _\[0-9\]+ = _\[0-9\]+ / _\[0-9\]+;" "slp2" } } */

4
gcc/tree-vect-slp.c
View file

@ -1214,14 +1214,14 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
}
}
if (phi_p
if ((phi_p || gimple_could_trap_p (stmt_info->stmt))
&& (gimple_bb (first_stmt_info->stmt)
!= gimple_bb (stmt_info->stmt)))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
"Build SLP failed: different BB for PHI "
"in %G", stmt);
"or possibly trapping operation in %G", stmt);
/* Mismatch. */
continue;
}