On 03/13/2018 09:32 AM, Jakub Jelinek wrote:
On Tue, Mar 13, 2018 at 09:24:11AM +0100, Martin Liška wrote:
On 03/12/2018 10:39 AM, Marc Glisse wrote:
On Mon, 12 Mar 2018, Martin Liška wrote:

This is fix for the PR that introduces a new target macro. Using the macro
one can say that a target has a fast mempcpy and thus it's preferred to be used
if possible.

Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
I also tested on x86_64-linux-gnu.

Ready to be installed?


2018-03-08  Martin Liska  <mli...@suse.cz>

     PR middle-end/81657
     * builtins.c (expand_builtin_memory_copy_args): Add new
     * config/i386/i386.h (TARGET_HAS_FAST_MEMPCPY_ROUTINE):
     New macro.

Shouldn't the macro be defined in a more specific case, for instance glibc on 
x86? Or do all known libc on x86 happen to provide a fast mempcpy?

That's Marc a very good question. Do we already have a glibc-related target 
If so, I would add this as one of these.

Yes, see e.g. TARGET_LIBC_HAS_FUNCTION target hook,
where in particular linux_libc_has_function deals with various C libraries.
Of course, in this case you need another target hook, that is dependent both
on the target backend and C library.

It would be nice to make the target hook a little bit more generic as well,
e.g. pass it enum builtin_function and query if it is fast, slow or
unknown, or even some kind of cost, where the caller could ask for cost of
BUILT_IN_MEMCPY and BUILT_IN_MEMPCPY and decide based on the relative costs.

Let me start with simple return enum value of FAST,SLOW,UNKNOWN. I've added new 
definition to gcc/config/gnu-user.h that will point to 
I would like to implement the function in gcc/targhooks.c, but I don't know how 
make ifdef according to target?

One another issue is that built_in_function is enum defined in tree.h. Thus 
I'll replace the
callback argument with int, that will be casted. One last issue: am I right 
that I'll have to define
TARGET_LIBC_FUNCTION_IMPLEMENTATION in each config file (similar to 



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