[Bug middle-end/37861] [4.3 Regression] Bogus array bounds warning
jamborm at gcc dot gnu dot org
gcc-bugzilla@gcc.gnu.org
Mon Nov 10 10:07:00 GMT 2008
------- Comment #8 from jamborm at gcc dot gnu dot org 2008-11-10 10:06 -------
The previous patch resulted into a regression on m32c-unknown-elf and
thus I prepared a less intrusive one below. See also:
* http://gcc.gnu.org/ml/gcc/2008-11/msg00058.html and
* http://gcc.gnu.org/ml/gcc-patches/2008-11/msg00353.html
The patch is pending approval in the mailing list.
2008-11-07 Martin Jambor <mjambor@suse.cz>
* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Do not check
for INDIRECT_REFs.
(forward_propagate_addr_into_variable_array_index): Check that the
offset is not computed from a MULT_EXPR, use is_gimple_assign rather
than the gimple code directly.
Index: gcc/tree-ssa-forwprop.c
===================================================================
--- gcc/tree-ssa-forwprop.c (revision 141673)
+++ gcc/tree-ssa-forwprop.c (working copy)
@@ -613,19 +613,27 @@ forward_propagate_addr_into_variable_arr
tree index;
gimple offset_def, use_stmt = gsi_stmt (*use_stmt_gsi);
- /* Try to find an expression for a proper index. This is either
- a multiplication expression by the element size or just the
- ssa name we came along in case the element size is one. */
+ /* Get the offset's defining statement. */
+ offset_def = SSA_NAME_DEF_STMT (offset);
+
+ /* Try to find an expression for a proper index. This is either a
+ multiplication expression by the element size or just the ssa name we
came
+ along in case the element size is one. In that case, however, we do not
+ allow multiplications because they can be computing index to a higher
+ level dimension (PR 37861). */
if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
- index = offset;
- else
{
- /* Get the offset's defining statement. */
- offset_def = SSA_NAME_DEF_STMT (offset);
+ if (is_gimple_assign (offset_def)
+ && gimple_assign_rhs_code (offset_def) == MULT_EXPR)
+ return false;
+ index = offset;
+ }
+ else
+ {
/* The statement which defines OFFSET before type conversion
must be a simple GIMPLE_ASSIGN. */
- if (gimple_code (offset_def) != GIMPLE_ASSIGN)
+ if (!is_gimple_assign (offset_def))
return false;
/* The RHS of the statement which defines OFFSET must be a
@@ -802,9 +810,6 @@ forward_propagate_addr_expr_1 (tree name
array_ref = TREE_OPERAND (def_rhs, 0);
if (TREE_CODE (array_ref) != ARRAY_REF
|| TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
- /* Avoid accessing hidden multidimensional arrays in this way or VRP
- might give out bogus warnings (see PR 37861) */
- || TREE_CODE (TREE_OPERAND (array_ref, 0)) == INDIRECT_REF
|| !integer_zerop (TREE_OPERAND (array_ref, 1)))
return false;
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37861
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