Fix disambiguation against .MASK_STORE

Alias analysis was treating .MASK_STORE as storing a full vector
which means we disambiguate against decls of smaller than vector size.
That's of course wrong and a similar issue was fixed for DSE already.
The following makes sure we set the size of the access to unknown
and only constrain max_size.

This fixes runtime execution FAILs of gfortran.dg/matmul_2.f90,
gfortran.dg/matmul_6.f90 and gfortran.dg/pr91577.f90 when using
AVX512 with full masked loop vectorization on Zen4.

	* tree-ssa-alias.cc (call_may_clobber_ref_p_1): For
	.MASK_STORE and friend set the size of the access to
	unknown.

(cherry picked from commit 8d3eb3ad5388d2f523e4a6f886c4b3364f77f51f)

diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc
index e0693e146bf318edd7751a4164cfd81ae6e1a937..89d4f8372b4e027460415abf6c4000237e069f6c 100644 (file)
--- a/gcc/tree-ssa-alias.cc
+++ b/gcc/tree-ssa-alias.cc
@@ -3072,6 +3072,9 @@ call_may_clobber_ref_p_1 (gcall *call, ao_ref *ref, bool tbaa_p)
          ao_ref lhs_ref;
          ao_ref_init_from_ptr_and_size (&lhs_ref, gimple_call_arg (call, 0),
                                         TYPE_SIZE_UNIT (TREE_TYPE (rhs)));
+         /* We cannot make this a known-size access since otherwise
+            we disambiguate against stores to decls that are smaller.  */
+         lhs_ref.size = -1;
          lhs_ref.ref_alias_set = lhs_ref.base_alias_set
            = tbaa_p ? get_deref_alias_set
                                   (TREE_TYPE (gimple_call_arg (call, 1))) : 0;