On Thu, Mar 27, 2014 at 2:49 PM, Ulrich Weigand <uweig...@de.ibm.com> wrote:
> Hello,
>
> when trying to build Ada for powerpc64le-linux, I ran into an ICE
> in fixup_args_size_notes.
>
> It turns out that the p8 fusion peephole acts on these two insns
> from the epilog sequence:
>
> (insn 1693 1078 1079 91 (set (reg:DI 7 7)
> (plus:DI (reg/f:DI 31 31)
> (const_int 65536 [0x10000]))) 82 {*adddi3_internal1}
> (nil))
> (insn 1079 1693 1511 91 (set (reg/f:DI 1 1)
> (mem/c:DI (plus:DI (reg:DI 7 7)
> (const_int -16096 [0xffffffffffffc120])) [233 %sfp+49440 S8
> A64])) 519 {*movdi_internal64}
> (expr_list:REG_DEAD (reg:DI 7 7)
> (expr_list:REG_ARGS_SIZE (const_int 0 [0])
> (nil))))
>
> and replaces them by:
>
> (insn 1776 1078 1777 91 (set (reg/f:DI 1 1)
> (plus:DI (reg/f:DI 31 31)
> (const_int 65536 [0x10000]))) -1
> (nil))
>
> (insn 1777 1776 1511 91 (set (reg/f:DI 1 1)
> (mem/c:DI (plus:DI (reg/f:DI 1 1)
> (const_int -16096 [0xffffffffffffc120])) [233 S8 A8])) -1
> (expr_list:REG_ARGS_SIZE (const_int 0 [0])
> (nil)))
>
> Then peephole common code thinks it needs to re-create the REG_ARGS_SIZE
> note and fails since the code is too complex for it to understand. (Which
> is reasonable since it doesn't know what value is being restored from the
> stack here.)
>
> However, the more fundamental problem seems to be that this transformation
> should be invalid anyway, since it creates an intermediate state where
> the stack pointer points to a location without proper backchain, which
> violates the ABI.
>
> The following patch fixes this by disabling the fusion peephole in those
> cases where it would introduce a new use of the stack pointer as temporary
> register.
>
> Tested on powerpc64le-linux. OK for mainline (and 4.8 after the big patch
> series is committed)?
>
> Bye,
> Ulrich
>
> ChangeLog:
>
> * config/rs6000/rs6000.c (fusion_gpr_load_p): Refuse optimization
> if it would clobber the stack pointer, even temporarily.
Okay.
Thanks, David
