From 6b56e645a7b481693fe6982f8f09ba2e07768bf8 Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Wed, 29 Jan 2025 15:09:35 +0100 Subject: middle-end/118692 - ICE with out-of-bound ref expansion The following guards the BIT_FIELD_REF expansion fallback for MEM_REFs of entities expanded to register (or constant) further, avoiding large out-of-bound offsets by, when the access does not overlap the base object, expanding the offset as if it were zero. PR middle-end/118692 * expr.cc (expand_expr_real_1): When expanding a MEM_REF as BIT_FIELD_REF avoid large offsets for accesses not overlapping the base object. * gcc.dg/pr118692.c: New testcase. --- gcc/expr.cc | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'gcc/expr.cc') diff --git a/gcc/expr.cc b/gcc/expr.cc index 7f3149b..10467f8 100644 --- a/gcc/expr.cc +++ b/gcc/expr.cc @@ -11806,6 +11806,14 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode, set_mem_size (temp, int_size_in_bytes (type)); return temp; } + /* When the access is fully outside of the underlying object + expand the offset as zero. This avoids out-of-bound + BIT_FIELD_REFs and generates smaller code for these cases + with UB. */ + type_size = tree_to_poly_uint64 (TYPE_SIZE_UNIT (type)); + if (!ranges_maybe_overlap_p (offset, type_size, 0, + GET_MODE_SIZE (DECL_MODE (base)))) + offset = 0; exp = build3 (BIT_FIELD_REF, type, base, TYPE_SIZE (type), bitsize_int (offset * BITS_PER_UNIT)); REF_REVERSE_STORAGE_ORDER (exp) = reverse; -- cgit v1.1