On Jun 12, 2011, at 4:03 AM, Richard Guenther wrote: > Btw, see tree.def which says > > /* Represents viewing something of one type as being of a second type. > This corresponds to an "Unchecked Conversion" in Ada and roughly to > the idiom *(type2 *)&X in C. The only operand is the value to be > viewed as being of another type. It is undefined if the type of the > input and of the expression have different sizes. > > This code may also be used within the LHS of a MODIFY_EXPR, in which > case no actual data motion may occur. TREE_ADDRESSABLE will be set in > this case and GCC must abort if it could not do the operation without > generating insns. */
I wasn't able to follow what this was trying to say. :-( No actual data motion may occur? The wording is weasely. Does it mean: Data motion does not occur when used on the LHS of a MODIFY_EXPR? If so, it should just directly state it.
