https://bugs.gentoo.org/956308 https://gcc.gnu.org/PR120358 https://gcc.gnu.org/cgit/gcc/commit/?id=aa5ae523e84a97bf3a582ea0fa73d959afa9b9c7 From aa5ae523e84a97bf3a582ea0fa73d959afa9b9c7 Mon Sep 17 00:00:00 2001 Message-ID: From: Richard Biener Date: Mon, 7 Jul 2025 15:13:38 +0200 Subject: [PATCH] tree-optimization/120358 - bogus PTA with structure access When we compute the constraint for something like MEM[(const struct QStringView &)&tok2 + 32] we go and compute what (const struct QStringView &)&tok2 + 32 points to and then add subvariables to its dereference that possibly fall in the range of the access according to the original refs size. In doing that we disregarded that the subvariable the starting address points to might not be aligned to it and thus the access might start at any point within that variable. The following conservatively adjusts the pruning of adjacent sub-variables to honor this. PR tree-optimization/120358 * tree-ssa-structalias.cc (get_constraint_for_1): Adjust pruning of sub-variables according to the imprecise known start offset. --- gcc/tree-ssa-structalias.cc | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/gcc/tree-ssa-structalias.cc b/gcc/tree-ssa-structalias.cc index deca44ae0bf3..0215243d5be9 100644 --- a/gcc/tree-ssa-structalias.cc +++ b/gcc/tree-ssa-structalias.cc @@ -3690,7 +3690,10 @@ get_constraint_for_1 (tree t, vec *results, bool address_p, size = -1; for (; curr; curr = vi_next (curr)) { - if (curr->offset - vi->offset < size) + /* The start of the access might happen anywhere + within vi, so conservatively assume it was + at its end. */ + if (curr->offset - (vi->offset + vi->size - 1) < size) { cs.var = curr->id; results->safe_push (cs); -- 2.50.0