On Thu, Apr 12, 2018 at 07:37:22PM +0200, Jakub Jelinek wrote:
> On Thu, Apr 12, 2018 at 05:29:35PM +0000, Wilco Dijkstra wrote:
> > > Depending on what you mean old, I see e.g. in 2010 power7 mempcpy got
> > > added,
> > > in 2013 other power versions, in 2016 s390*, etc. Doing a decent mempcpy
> > > isn't hard if you have asm version of memcpy and one spare register.
> >
> > More mempcpy implementations have been added in recent years indeed, but
> > almost all
> > add an extra copy of the memcpy code rather than using a single combined
> > implementation.
> > That means it is still better to call memcpy (which is frequently used and
> > thus likely in L1/L2)
> > rather than mempcpy (which is more likely to be cold and thus not cached).
>
> That really depends, usually when some app uses mempcpy, it uses it very
> heavily. And all the proposed patches do is honor what the user asked, if
> you use memcpy () + n, we aren't transforming that into mempcpy behind the
> user's back.
>
> Anyway, here is what I think Richard was asking for, that I'm currently
> bootstrapping/regtesting. It can be easily combined with Martin's target
> hook if needed, or do it only for
> endp == 1 && target != const0_rtx && CALL_EXPR_TAILCALL (exp)
> etc.
>
> 2018-04-12 Martin Liska <mli...@suse.cz>
> Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/81657
> * expr.h (enum block_op_methods): Add BLOCK_OP_NO_LIBCALL_RET.
> * expr.c (emit_block_move_hints): Handle BLOCK_OP_NO_LIBCALL_RET.
> * builtins.c (expand_builtin_memory_copy_args): Use
> BLOCK_OP_NO_LIBCALL_RET method for mempcpy with non-ignored target,
> handle dest_addr == pc_rtx.
>
> * gcc.dg/string-opt-1.c: Remove bogus comment. Expect a mempcpy
> call.
Successfully bootstrapped/regtested on x86_64-linux and i686-linux.
Jakub
