[gcc r13-7442] Fix disambiguation against .MASK_STORE

[Richard Biener]

https://gcc.gnu.org/g:6955c36ab313492bc0ea1aa98085193a32e0ed4e

commit r13-7442-g6955c36ab313492bc0ea1aa98085193a32e0ed4e
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Jun 12 14:09:45 2023 +0200

    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:
---
 gcc/tree-ssa-alias.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc
index e0693e146bf..89d4f8372b4 100644
--- 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;