https://gcc.gnu.org/g:d48273f06fee3886b05ce4d10b4db3d52f1991dc
commit r15-3317-gd48273f06fee3886b05ce4d10b4db3d52f1991dc
Author: Richard Biener <rguent...@suse.de>
Date: Fri Aug 30 09:50:32 2024 +0200
Avoid division by zero via constant_multiple_p
With recent SLP vectorization patches I see RISC-V divison by zero
for gfortran.dg/matmul_10.f90 and others in get_group_load_store_type
which does
&& can_div_trunc_p (group_size
* LOOP_VINFO_VECT_FACTOR (loop_vinfo) -
gap,
nunits, &tem, &remain)
&& (known_eq (remain, 0u)
|| (constant_multiple_p (nunits, remain, &num)
&& (vector_vector_composition_type (vectype, num,
&half_vtype)
!= NULL_TREE))))
overrun_p = false;
where for [2, 2] / [0, 2] the condition doesn't reflect what we
are trying to test - that, when remain is zero or, when non-zero,
nunits is a multiple of remain, we can avoid touching a gap via
loading smaller pieces and vector composition.
It isn't safe to change the known_eq to maybe_eq so instead
require known_ne (remain, 0u) before doing constant_multiple_p.
There's the corresponding code in vectorizable_load that's known
to have a latent similar issue, so sync that up as well.
* tree-vect-stmts.cc (get_group_load_store_type): Check
known_ne (remain, 0u) before doing constant_multiple_p.
(vectorizable_load): Likewise.
Diff:
---
gcc/tree-vect-stmts.cc | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 03c65f0958c6..72a29c0584b9 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -2126,7 +2126,8 @@ get_group_load_store_type (vec_info *vinfo, stmt_vec_info
stmt_info,
* LOOP_VINFO_VECT_FACTOR (loop_vinfo) - gap,
nunits, &tem, &remain)
&& (known_eq (remain, 0u)
- || (constant_multiple_p (nunits, remain, &num)
+ || (known_ne (remain, 0u)
+ && constant_multiple_p (nunits, remain, &num)
&& (vector_vector_composition_type (vectype, num,
&half_vtype)
!= NULL_TREE))))
@@ -11519,7 +11520,8 @@ vectorizable_load (vec_info *vinfo,
{
/* remain should now be > 0 and < nunits. */
unsigned num;
- if (constant_multiple_p (nunits, remain, &num))
+ if (known_ne (remain, 0u)
+ && constant_multiple_p (nunits, remain, &num))
{
tree ptype;
new_vtype
