On 6 February 2014 16:42:05 Jakub Jelinek <ja...@redhat.com> wrote:
Hi!
As discussed on IRC, this patch introduces two new attributes,
so that the C library (and other headers) have a way to
a) tell the compiler something about functions like aligned_alloc
or memalign
b) tell the compiler the alignment of pointers returned say by malloc
Ok for trunk if bootstrap/regtest passes?
+/* Return the propagation value for functions with assume_aligned
+ or alloc_aligned attribute. */
+
+static prop_value_t
+bit_value_alloc_assume_aligned_attribute (gimple stmt, tree attr,
+ prop_value_t ptrval,
+ bool alloc_aligned)
+{
+ tree lhs = gimple_call_lhs (stmt), align, misalign = NULL_TREE;
+ tree type = TREE_TYPE (lhs);
+ unsigned HOST_WIDE_INT aligni, misaligni = 0;
+ prop_value_t alignval;
+ double_int value, mask;
+ prop_value_t val;
Do we have an optimization that moves most of the above down..
+ if (ptrval.lattice_val == UNDEFINED)
+ return ptrval;
+ gcc_assert ((ptrval.lattice_val == CONSTANT
+ && TREE_CODE (ptrval.value) == INTEGER_CST)
+ || ptrval.mask.is_minus_one ());
+ if (TREE_VALUE (attr) == NULL_TREE)
+ return ptrval;
+ attr = TREE_VALUE (attr);
+ align = TREE_VALUE (attr);
+ if (!tree_fits_uhwi_p (align))
+ return ptrval;
+ aligni = tree_to_uhwi (align);
+ if (alloc_aligned)
+ {
+ if (aligni == 0 || aligni > gimple_call_num_args (stmt))
+ return ptrval;
+ align = gimple_call_arg (stmt, aligni - 1);
+ if (!tree_fits_uhwi_p (align))
+ return ptrval;
+ aligni = tree_to_uhwi (align);
+ }
+ if (aligni <= 1
+ || (aligni & (aligni - 1)) != 0)
+ return ptrval;
+ if (!alloc_aligned && TREE_CHAIN (attr) && TREE_VALUE (TREE_CHAIN (attr)))
+ {
+ misalign = TREE_VALUE (TREE_CHAIN (attr));
+ if (!tree_fits_uhwi_p (misalign))
+ return ptrval;
+ misaligni = tree_to_uhwi (misalign);
+ if (misaligni >= aligni)
+ return ptrval;
+ }
.. here, btw? Or would one have to do that manually?
Just curious.
Thanks,
+ align = build_int_cst_type (type, -aligni);
+ alignval = get_value_for_expr (align, true);
+ bit_value_binop_1 (BIT_AND_EXPR, type, &value, &mask,
+ type, value_to_double_int (ptrval), ptrval.mask,
+ type, value_to_double_int (alignval), alignval.mask);
+ if (!mask.is_minus_one ())
+ {
+ val.lattice_val = CONSTANT;
+ val.mask = mask;
+ gcc_assert ((mask.low & (aligni - 1)) == 0);
+ gcc_assert ((value.low & (aligni - 1)) == 0);
+ value.low |= misaligni;
+ /* ??? Delay building trees here. */
+ val.value = double_int_to_tree (type, value);
+ }
+ else
+ {
+ val.lattice_val = VARYING;
+ val.value = NULL_TREE;
+ val.mask = double_int_minus_one;
+ }
+ return val;
+}
+
/* Evaluate statement STMT.
Valid only for assignments, calls, conditionals, and switches. */
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