Hi!
The patch I've just posted wasn't enough, because stmt_kills_ref_p_1
only did something if base == ref->base, but in the case of the dtors
base and ref->base are often MEM_REFs, which aren't equal, but they
just operand_equal_p. And, for MEM_REFs, we don't even need to require
that the two MEM_REFs operand_equal_p, it is enough if the first operand
of both is the same, we don't need to care about either of the two types
(TBAA and MEM_REF's type), nor sizes, and can even handle different offset
arguments. On IRC we've been talking with Richard about adding a predicate
function whether addresses are the same, but as that predicate would
necessarily require that the MEM_REF offset is the same constant (ignoring
the TBAA type on it), that would disallow handling different offsets,
so the function now performs all the checking inline.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2013-04-02 Jakub Jelinek <ja...@redhat.com>
PR c++/34949
* tree-ssa-alias.c (stmt_kills_ref_p_1): If base != ref->base,
call operand_equal_p on them or for MEM_REFs just compare
first argument for equality and attempt to deal even with differing
offsets.
--- gcc/tree-ssa-alias.c.jj 2013-03-18 12:16:59.000000000 +0100
+++ gcc/tree-ssa-alias.c 2013-03-27 17:09:28.230216081 +0100
@@ -1870,20 +1870,51 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref
&& !stmt_can_throw_internal (stmt))
{
tree base, lhs = gimple_get_lhs (stmt);
- HOST_WIDE_INT size, offset, max_size;
+ HOST_WIDE_INT size, offset, max_size, ref_offset = ref->offset;
base = get_ref_base_and_extent (lhs, &offset, &size, &max_size);
/* We can get MEM[symbol: sZ, index: D.8862_1] here,
so base == ref->base does not always hold. */
- if (base == ref->base)
+ if (base != ref->base)
{
- /* For a must-alias check we need to be able to constrain
- the access properly. */
- if (size != -1 && size == max_size)
+ /* If both base and ref->base are MEM_REFs, only compare the
+ first operand, and if the second operand isn't equal constant,
+ try to add the offsets into offset and ref_offset. */
+ if (TREE_CODE (base) == MEM_REF && TREE_CODE (ref->base) == MEM_REF
+ && operand_equal_p (TREE_OPERAND (base, 0),
+ TREE_OPERAND (ref->base, 0), 0))
{
- if (offset <= ref->offset
- && offset + size >= ref->offset + ref->max_size)
- return true;
+ if (!tree_int_cst_equal (TREE_OPERAND (base, 0),
+ TREE_OPERAND (ref->base, 0)))
+ {
+ double_int off1 = mem_ref_offset (base);
+ off1 = off1.alshift (BITS_PER_UNIT == 8
+ ? 3 : exact_log2 (BITS_PER_UNIT),
+ HOST_BITS_PER_DOUBLE_INT);
+ off1 = off1 + double_int::from_shwi (offset);
+ double_int off2 = mem_ref_offset (ref->base);
+ off2 = off2.alshift (BITS_PER_UNIT == 8
+ ? 3 : exact_log2 (BITS_PER_UNIT),
+ HOST_BITS_PER_DOUBLE_INT);
+ off2 = off2 + double_int::from_shwi (ref_offset);
+ if (off1.fits_shwi () && off2.fits_shwi ())
+ {
+ offset = off1.to_shwi ();
+ ref_offset = off2.to_shwi ();
+ }
+ else
+ size = -1;
+ }
}
+ else if (!operand_equal_p (base, ref->base, 0))
+ size = -1;
+ }
+ /* For a must-alias check we need to be able to constrain
+ the access properly. */
+ if (size != -1 && size == max_size)
+ {
+ if (offset <= ref_offset
+ && offset + size >= ref_offset + ref->max_size)
+ return true;
}
}
Jakub
