On Mon, Jul 11, 2016 at 03:26:46PM +0200, Ulrich Weigand wrote:
> However, there still seems to be another underlying problem: reload
> should never generate invalid instructions. (Playing with '?' to
> fix *inefficient* instructions is fine, but we shouldn't rely on '?'
> to fix *invalid* instructions.)
>
> If reload -for whatever reason- wants to emit a vr->gpr move, then it
> should generate a valid instruction sequence to do so, via secondary
> reloads if necessary. I think it would be a good idea to investigate
> why that isn't happening in this test case. [ There is a chance that
> the underlying bug will reappear in a different context, even after
> the '?' change is applied. ]
The vr->gpr move uses secondary memory. The memory allocated by
assign_stack_local, called from get_secondary_memory is
(mem/c:V16QI (plus:DI (reg/f:DI 113 sfp)
(const_int 32 [0x20])) [0 S16 A128])
and that is incorrectly simplified by eliminate_regs to
(mem/c:V16QI (reg/f:DI 1 1))
for use by the strict_memory_address_space_p check, which of course
then passes.
eliminate_regs sees this entry in the elimination table:
(gdb) p *ep
$7 = {from = 113, to = 1, initial_offset = -32, can_eliminate = 1,
can_eliminate_previous = 1, offset = -32, previous_offset = -32,
ref_outside_mem = 0, from_rtx = 0x7ffff688a300, to_rtx = 0x7ffff688a2e8}
The offset in the elimination table was correct before
get_secondary_memory called assign_stack_local, but not after
frame_offset was changed when allocating a new stack slot.
--
Alan Modra
Australia Development Lab, IBM
