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From 24f5b59f5c9418d39087b36dd0d275f71ac4dca5 Mon Sep 17 00:00:00 2001
From: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Fri, 20 May 2011 15:08:56 +0000
Subject: [PATCH] 2011-05-20 Richard Guenther <rguenther@suse.de>
PR tree-optimization/49079
* tree-dfa.c (get_ref_base_and_extent): Handle view-converting
MEM_REFs correctly for the trailing array access detection.
Special case constants the same way as decls for overall size
constraining.
* gcc.dg/torture/pr49079.c: New testcase.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_6-branch@173955 138bc75d-0d04-0410-961f-82ee72b054a4
index 0efa0eb..dcb39c1 100644
new file mode 100644
index 0000000..1b53d3c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr49079.c
@@ -0,0 +1,31 @@
+/* { dg-do run } */
+
+extern void abort (void);
+
+struct Ustr
+{
+ unsigned char data[1];
+};
+
+static unsigned int
+ustr_xi__embed_val_get(const unsigned char *data)
+{
+ return (unsigned int)data[0];
+}
+
+int __attribute__((noinline)) zero(void) { return 0; }
+
+static unsigned int
+ustr_len(const struct Ustr *s1)
+{
+ return ustr_xi__embed_val_get(s1->data + 1 + zero());
+}
+
+int
+main()
+{
+ if (ustr_len (((struct Ustr *) "\x01" "\x0002" "s2")) != 2)
+ abort ();
+
+ return 0;
+}
diff --git a/gcc/tree-dfa.c b/gcc/tree-dfa.c
index 6490c5e..2dacd44 100644
--- a/gcc/tree-dfa.c
+++ b/gcc/tree-dfa.c
@@ -709,6 +709,7 @@ 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;
+ tree base_type;
/* First get the final access size from just the outermost expression. */
if (TREE_CODE (exp) == COMPONENT_REF)
@@ -739,6 +740,8 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
and find the ultimate containing object. */
while (1)
{
+ base_type = TREE_TYPE (exp);
+
switch (TREE_CODE (exp))
{
case BIT_FIELD_REF:
@@ -926,9 +929,16 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
the array. The simplest way to conservatively deal with this
is to punt in the case that offset + maxsize reaches the
base type boundary. This needs to include possible trailing padding
- that is there for alignment purposes.
+ that is there for alignment purposes. */
+
+ if (seen_variable_array_ref
+ && maxsize != -1
+ && (!host_integerp (TYPE_SIZE (base_type), 1)
+ || (bit_offset + maxsize
+ == (signed) TREE_INT_CST_LOW (TYPE_SIZE (base_type)))))
+ maxsize = -1;
- That is of course only true if the base object is not a decl. */
+ /* In case of a decl or constant base object we can do better. */
if (DECL_P (exp))
{
@@ -938,12 +948,14 @@ get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
&& host_integerp (DECL_SIZE (exp), 1))
maxsize = TREE_INT_CST_LOW (DECL_SIZE (exp)) - bit_offset;
}
- else 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))))))
- maxsize = -1;
+ else if (CONSTANT_CLASS_P (exp))
+ {
+ /* If maxsize is unknown adjust it according to the size of the
+ base type constant. */
+ if (maxsize == -1
+ && host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1))
+ maxsize = TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp))) - bit_offset;
+ }
/* ??? Due to negative offsets in ARRAY_REF we can end up with
negative bit_offset here. We might want to store a zero offset
--
1.7.0.4
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