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Re: Teach sccvn about constant vars
Hi,
this patch fixes the ignored low_bound in array_ref folding and converts arithmetics
to double_int.
Note that the code (without the low_bound bug) exist in another two copies - in
fold_read_from_constant_string and in expr.c
I hope to remove the expr.c code by end of week (we need to process the remaining
sccvn patch and should be there). In expr.c I can also put in the INTEGER_CST
code but since this is used by frontend too we sould miss optimization when
lower bound and index are variables. So I guess I can keep the busy operation
there and remove the call from tree-ssa-ccp that should be redundant now.
Boostrapped/regtested x86_64, OK?
Honza
* tree-ssa-ccp.c (fold_const_aggregate_ref): Fix handling of array_ref_low_bound
in string access folding.
Index: tree-ssa-ccp.c
===================================================================
--- tree-ssa-ccp.c (revision 163947)
+++ tree-ssa-ccp.c (working copy)
@@ -1398,14 +1398,27 @@ fold_const_aggregate_ref (tree t)
}
/* Fold read from constant string. */
- if (TREE_CODE (ctor) == STRING_CST)
+ if (TREE_CODE (ctor) == STRING_CST
+ && TREE_CODE (idx) == INTEGER_CST)
{
+ tree low_bound = array_ref_low_bound (t);
+ double_int low_bound_cst;
+ double_int index_cst;
+ double_int length_cst;
+ bool signed_p = TYPE_UNSIGNED (TREE_TYPE (idx));
+
+ if (TREE_CODE (low_bound) != INTEGER_CST)
+ return NULL_TREE;
+ low_bound_cst = tree_to_double_int (low_bound);
+ index_cst = tree_to_double_int (idx);
+ length_cst = uhwi_to_double_int (TREE_STRING_LENGTH (ctor));
+ double_int_sub (index_cst, low_bound_cst);
if ((TYPE_MODE (TREE_TYPE (t))
== TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
&& (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
== MODE_INT)
&& GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1
- && compare_tree_int (idx, TREE_STRING_LENGTH (ctor)) < 0)
+ && double_int_cmp (index_cst, length_cst, signed_p) < 0)
return build_int_cst_type (TREE_TYPE (t),
(TREE_STRING_POINTER (ctor)
[TREE_INT_CST_LOW (idx)]));