+
+ /* Initially, maxsize is the same as the accessed element size.
+ In the following it will only grow (or become -1). */
+ maxsize = bitsize;
+
+ /* Compute cumulative bit-offset for nested component-refs and array-refs,
+ and find the ultimate containing object. */
+ while (1)
+ {
+ switch (TREE_CODE (exp))
+ {
+ case BIT_FIELD_REF:
+ bit_offset += TREE_INT_CST_LOW (TREE_OPERAND (exp, 2));
+ break;
+
+ case COMPONENT_REF:
+ {
+ tree field = TREE_OPERAND (exp, 1);
+ tree this_offset = component_ref_field_offset (exp);
+
+ if (this_offset
+ && TREE_CODE (this_offset) == INTEGER_CST
+ && host_integerp (this_offset, 0))
+ {
+ HOST_WIDE_INT hthis_offset = TREE_INT_CST_LOW (this_offset);
+ hthis_offset *= BITS_PER_UNIT;
+ hthis_offset
+ += TREE_INT_CST_LOW (DECL_FIELD_BIT_OFFSET (field));
+ bit_offset += hthis_offset;
+
+ /* If we had seen a variable array ref already and we just
+ referenced the last field of a struct or a union member
+ then we have to adjust maxsize by the padding at the end
+ of our field. */
+ if (seen_variable_array_ref
+ && maxsize != -1)
+ {
+ tree stype = TREE_TYPE (TREE_OPERAND (exp, 0));
+ tree next = TREE_CHAIN (field);
+ while (next && TREE_CODE (next) != FIELD_DECL)
+ next = TREE_CHAIN (next);
+ if (!next
+ || TREE_CODE (stype) != RECORD_TYPE)
+ {
+ tree fsize = DECL_SIZE_UNIT (field);
+ tree ssize = TYPE_SIZE_UNIT (stype);
+ if (host_integerp (fsize, 0)
+ && host_integerp (ssize, 0))
+ maxsize += ((TREE_INT_CST_LOW (ssize)
+ - TREE_INT_CST_LOW (fsize))
+ * BITS_PER_UNIT - hthis_offset);
+ else
+ maxsize = -1;
+ }
+ }
+ }
+ else
+ {
+ tree csize = TYPE_SIZE (TREE_TYPE (TREE_OPERAND (exp, 0)));
+ /* We need to adjust maxsize to the whole structure bitsize.
+ But we can subtract any constant offset seen so far,
+ because that would get us out of the structure otherwise. */
+ if (maxsize != -1 && csize && host_integerp (csize, 1))
+ maxsize = TREE_INT_CST_LOW (csize) - bit_offset;
+ else
+ maxsize = -1;
+ }
+ }
+ break;
+
+ case ARRAY_REF:
+ case ARRAY_RANGE_REF:
+ {
+ tree index = TREE_OPERAND (exp, 1);
+ tree low_bound, unit_size;
+
+ /* If the resulting bit-offset is constant, track it. */
+ if (TREE_CODE (index) == INTEGER_CST
+ && host_integerp (index, 0)
+ && (low_bound = array_ref_low_bound (exp),
+ host_integerp (low_bound, 0))
+ && (unit_size = array_ref_element_size (exp),
+ host_integerp (unit_size, 1)))
+ {
+ HOST_WIDE_INT hindex = TREE_INT_CST_LOW (index);
+
+ hindex -= TREE_INT_CST_LOW (low_bound);
+ hindex *= TREE_INT_CST_LOW (unit_size);
+ hindex *= BITS_PER_UNIT;
+ bit_offset += hindex;
+
+ /* An array ref with a constant index up in the structure
+ hierarchy will constrain the size of any variable array ref
+ lower in the access hierarchy. */
+ seen_variable_array_ref = false;
+ }
+ else
+ {
+ tree asize = TYPE_SIZE (TREE_TYPE (TREE_OPERAND (exp, 0)));
+ /* We need to adjust maxsize to the whole array bitsize.
+ But we can subtract any constant offset seen so far,
+ because that would get us outside of the array otherwise. */
+ if (maxsize != -1 && asize && host_integerp (asize, 1))
+ maxsize = TREE_INT_CST_LOW (asize) - bit_offset;
+ else
+ maxsize = -1;
+
+ /* Remember that we have seen an array ref with a variable
+ index. */
+ seen_variable_array_ref = true;
+ }
+ }
+ break;
+
+ case REALPART_EXPR:
+ break;
+
+ case IMAGPART_EXPR:
+ bit_offset += bitsize;
+ break;
+
+ case VIEW_CONVERT_EXPR:
+ break;
+
+ default:
+ goto done;
+ }
+
+ exp = TREE_OPERAND (exp, 0);
+ }
+ done:
+
+ /* We need to deal with variable arrays ending structures such as
+ struct { int length; int a[1]; } x; x.a[d]
+ struct { struct { int a; int b; } a[1]; } x; x.a[d].a
+ struct { struct { int a[1]; } a[1]; } x; x.a[0][d], x.a[d][0]
+ struct { int len; union { int a[1]; struct X x; } u; } x; x.u.a[d]
+ where we do not know maxsize for variable index accesses to
+ 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 of course only true if the base object is not a decl. */
+
+ if (DECL_P (exp))
+ {
+ /* If maxsize is unknown adjust it according to the size of the
+ base decl. */
+ if (maxsize == -1
+ && 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;
+
+ /* ??? Due to negative offsets in ARRAY_REF we can end up with
+ negative bit_offset here. We might want to store a zero offset
+ in this case. */
+ *poffset = bit_offset;
+ *psize = bitsize;
+ *pmax_size = maxsize;
+
+ return exp;
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