+/* Return OFFSET if XEXP (MEM, 0) - OFFSET is known to be ALIGN
+ bits aligned for 0 <= OFFSET < ALIGN / BITS_PER_UNIT, or
+ -1 if not known. */
+
+int
+get_mem_align_offset (rtx mem, unsigned int align)
+{
+ tree expr;
+ unsigned HOST_WIDE_INT offset;
+
+ /* This function can't use
+ if (!MEM_EXPR (mem) || !MEM_OFFSET_KNOWN_P (mem)
+ || (MAX (MEM_ALIGN (mem),
+ get_object_alignment (MEM_EXPR (mem), align))
+ < align))
+ return -1;
+ else
+ return (- MEM_OFFSET (mem)) & (align / BITS_PER_UNIT - 1);
+ for two reasons:
+ - COMPONENT_REFs in MEM_EXPR can have NULL first operand,
+ for <variable>. get_inner_reference doesn't handle it and
+ even if it did, the alignment in that case needs to be determined
+ from DECL_FIELD_CONTEXT's TYPE_ALIGN.
+ - it would do suboptimal job for COMPONENT_REFs, even if MEM_EXPR
+ isn't sufficiently aligned, the object it is in might be. */
+ gcc_assert (MEM_P (mem));
+ expr = MEM_EXPR (mem);
+ if (expr == NULL_TREE || !MEM_OFFSET_KNOWN_P (mem))
+ return -1;
+
+ offset = MEM_OFFSET (mem);
+ if (DECL_P (expr))
+ {
+ if (DECL_ALIGN (expr) < align)
+ return -1;
+ }
+ else if (INDIRECT_REF_P (expr))
+ {
+ if (TYPE_ALIGN (TREE_TYPE (expr)) < (unsigned int) align)
+ return -1;
+ }
+ else if (TREE_CODE (expr) == COMPONENT_REF)
+ {
+ while (1)
+ {
+ tree inner = TREE_OPERAND (expr, 0);
+ tree field = TREE_OPERAND (expr, 1);
+ tree byte_offset = component_ref_field_offset (expr);
+ tree bit_offset = DECL_FIELD_BIT_OFFSET (field);
+
+ if (!byte_offset
+ || !host_integerp (byte_offset, 1)
+ || !host_integerp (bit_offset, 1))
+ return -1;
+
+ offset += tree_low_cst (byte_offset, 1);
+ offset += tree_low_cst (bit_offset, 1) / BITS_PER_UNIT;
+
+ if (inner == NULL_TREE)
+ {
+ if (TYPE_ALIGN (DECL_FIELD_CONTEXT (field))
+ < (unsigned int) align)
+ return -1;
+ break;
+ }
+ else if (DECL_P (inner))
+ {
+ if (DECL_ALIGN (inner) < align)
+ return -1;
+ break;
+ }
+ else if (TREE_CODE (inner) != COMPONENT_REF)
+ return -1;
+ expr = inner;
+ }
+ }
+ else
+ return -1;
+
+ return offset & ((align / BITS_PER_UNIT) - 1);