On Wed, 2005-02-16 at 16:49 +0100, Theodore Papadopoulo wrote: > On Wed, 2005-02-16 at 14:25 +0100, Richard Guenther wrote: > > On Wed, 16 Feb 2005, Paul Schlie wrote: > > > Yes, of course, but it is the C frontent that is producing > > &a + (int *)-4, not me. I'm just trying to work around this... > > > > In fact, it is c-common.c:2289 that does -4 -> (int *)-4 > > conversion, but pointer_int_sum is already called with PLUS_EXPR. > > build_unary_op unconditionally expands &x[y] to x+y, regardless > > of the sign of y. Of course the standard says that they are equal. > > But is &x[-1] == x + (int *)4*(int *)-1 ? From this follows that > > we have no way to convert this back to &x[-1], as we loose the > > sign information by the (int *) cast. > > Reading this thread, I keep wondering why this cast to an (int*). It > should be a simple int no ?? If the intent is to have both operands of > the PLUS to have the same type then it might be a counter-example for > this rule (but I do understand that it would require specific patterns > for pointer addition which is fairly stupid in general).... The cast is to ensure that both operands of the PLUS_EXPR have the same type.
I looked for a little while into fixing this by having a new tree node (PLUS_POINTER_EXPR or whatever it was) which took a pointer and an integer. The amount of work necessary to get that going is mind-boggling. I gave up. jeff
