When the first pointer happens to be a pointer to a STRING_CST we give up too early since the 2nd pointer handling could still end up with a DECL for example which can disambiguate against a STRING_CST just fine.
Boostrapped and tested on x86_64-unknown-linux-gnu, pushed. * tree-ssa-alias.cc (ptr_derefs_may_alias_p): If ptr1 points to a constant continue checking ptr2. --- gcc/tree-ssa-alias.cc | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc index 390cd875074..b4c65da5718 100644 --- a/gcc/tree-ssa-alias.cc +++ b/gcc/tree-ssa-alias.cc @@ -349,7 +349,9 @@ ptr_derefs_may_alias_p (tree ptr1, tree ptr2) else if (base && DECL_P (base)) return ptr_deref_may_alias_decl_p (ptr2, base); - else + /* Try ptr2 when ptr1 points to a constant. */ + else if (base + && !CONSTANT_CLASS_P (base)) return true; } if (TREE_CODE (ptr2) == ADDR_EXPR) -- 2.35.3