From 00e850451cfa2fee4f2c52442896522a6b61d3a1 Mon Sep 17 00:00:00 2001 From: Richard Guenther Date: Fri, 10 Feb 2006 13:05:48 +0000 Subject: tree-dfa.c (get_ref_base_and_extent): When computing maxsize deal with structures that end in implicitly variable... 2006-02-10 Richard Guenther * tree-dfa.c (get_ref_base_and_extent): When computing maxsize deal with structures that end in implicitly variable sized arrays. From-SVN: r110834 --- gcc/tree-dfa.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'gcc/tree-dfa.c') diff --git a/gcc/tree-dfa.c b/gcc/tree-dfa.c index 19453780d42..8339a942831 100644 --- a/gcc/tree-dfa.c +++ b/gcc/tree-dfa.c @@ -913,6 +913,7 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset, HOST_WIDE_INT maxsize = -1; tree size_tree = NULL_TREE; tree bit_offset = bitsize_zero_node; + bool seen_variable_array_ref = false; gcc_assert (!SSA_VAR_P (exp)); @@ -1004,6 +1005,11 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset, fold_convert (bitsizetype, index), bitsize_unit_node); bit_offset = size_binop (PLUS_EXPR, bit_offset, index); + + /* An array ref with a constant index up in the structure + hierarchy will constrain the size of any variable array ref + lower in the access hierarchy. */ + seen_variable_array_ref = false; } else { @@ -1019,6 +1025,10 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset, } else maxsize = -1; + + /* Remember that we have seen an array ref with a variable + index. */ + seen_variable_array_ref = true; } } break; @@ -1043,6 +1053,21 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset, } done: + /* We need to deal with variable arrays ending structures such as + struct { int length; int a[1]; } x; x.a[d] + struct { struct { int a; int b; } a[1]; } x; x.a[d].a + struct { struct { int a[1]; } a[1]; } x; x.a[0][d], x.a[d][0] + 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. */ + if (seen_variable_array_ref + && maxsize != -1 + && host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1) + && TREE_INT_CST_LOW (bit_offset) + maxsize + == TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp)))) + maxsize = -1; + /* ??? Due to negative offsets in ARRAY_REF we can end up with negative bit_offset here. We might want to store a zero offset in this case. */ -- cgit v1.2.1