https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101437
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:f6dde32b9d487dd6e343d0a1e1d1f60783f5e735 commit r12-2320-gf6dde32b9d487dd6e343d0a1e1d1f60783f5e735 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Jul 15 10:17:06 2021 +0200 gimplify: Fix endless recursion on volatile empty type reads/writes [PR101437] Andrew's recent change to optimize away during gimplification not just assignments of zero sized types, but also assignments of empty types, caused infinite recursion in the gimplifier. If such assignment is optimized away, we gimplify separately the to_p and from_p operands and throw away the result. When gimplifying the operand that is volatile, we run into the gimplifier code below, which has different handling for types with non-BLKmode mode, tries to gimplify those as vol.N = expr, and for BLKmode just throws those away. Zero sized types will always have BLKmode and so are fine, but for the non-BLKmode ones like struct S in the testcase, the vol.N = expr gimplification will reach again the gimplify_modify_expr code, see it is assignment of empty type and will gimplify again vol.N separately (non-volatile, so ok) and expr, on which it will recurse again. The following patch breaks that infinite recursion by ignoring bare volatile loads from empty types. If a volatile load or store for aggregates are supposed to be member-wise loads or stores, then there are no non-padding members in the empty types that should be copied and so it is probably ok. 2021-07-15 Jakub Jelinek <ja...@redhat.com> PR middle-end/101437 * gimplify.c (gimplify_expr): Throw away volatile reads from empty types even if they have non-BLKmode TYPE_MODE. * gcc.c-torture/compile/pr101437.c: New test.
