diff options
Diffstat (limited to 'gcc/tree-dfa.c')
| -rw-r--r-- | gcc/tree-dfa.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/gcc/tree-dfa.c b/gcc/tree-dfa.c index 5241e64c929..082ac082bf3 100644 --- a/gcc/tree-dfa.c +++ b/gcc/tree-dfa.c @@ -801,6 +801,7 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset, tree size_tree = NULL_TREE; HOST_WIDE_INT bit_offset = 0; bool seen_variable_array_ref = false; + bool seen_union = false; gcc_assert (!SSA_VAR_P (exp)); @@ -844,6 +845,9 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset, tree field = TREE_OPERAND (exp, 1); tree this_offset = component_ref_field_offset (exp); + if (TREE_CODE (TREE_TYPE (TREE_OPERAND (exp, 0))) == UNION_TYPE) + seen_union = true; + if (this_offset && TREE_CODE (this_offset) == INTEGER_CST) { HOST_WIDE_INT hthis_offset = tree_low_cst (this_offset, 0); @@ -934,12 +938,22 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset, where we do not know maxsize for variable index accesses to the array. The simplest way to conservatively deal with this is to punt in the case that offset + maxsize reaches the - base type boundary. */ + base type boundary. + + Unfortunately this is difficult to determine reliably when unions are + involved and so we are conservative in such cases. + + FIXME: This approach may be too conservative, we probably want to at least + check that the union is the last field/element at its level or even + propagate the calculated offsets back up the access chain and check + there. */ + if (seen_variable_array_ref - && maxsize != -1 - && host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1) - && bit_offset + maxsize - == (signed)TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp)))) + && (seen_union + || (maxsize != -1 + && host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1) + && bit_offset + maxsize + == (signed) TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp)))))) maxsize = -1; /* ??? Due to negative offsets in ARRAY_REF we can end up with |