Re: [PATCH] Fixes tree-loop-distribute-patterns issues

[Roland McGrath <roland at hack dot frob dot com>]

> > I'm a little worried about the fragility of the test, but if it doesn't
> > optimize to memset, then it may not optimize the internal implementation
> > to memset, and therefore we need not avoid the benefit of the optimization.
> >
> > I think this is a good approach, but we will have to see how it plays out
> > and if it is robust enough.
> 
> We might make it more robust (maybe trying different loops), do you think it 
> is worth to push more tests?

I had not contemplated this sort of configure check and I don't think it's
what we want at all.  It doesn't matter whether the compiler actually
transforms a particular case into a call.  All that matters is that the
compiler understands
__attribute__ ((optimize ("-fno-tree-loop-distribute-patterns"))).
If it does, then we'll use it every place we think it might matter.

> 	* include/libc-symbols.h (libc_disable_loop_to_calls): Define to
> 	disable loop transformation to library calls.

The log line for this is just, "New macro."  Details about its purpose
belong in a comment at the definition site.

We only use the "libc_" prefix on macros when they are ones that
specifically apply to libc proper but not other contexts of the same code
(i.e. are defined differently based on NOT_IN_libc).

The name I'd favor is "inhibit_loop_to_libcall".

> 	* string/memmove.c (MEMMOVE): Disable loop transformation to avoid
> 	recursive call.
> 	* string/memset.c (memset): Likewise.
> 	* string/test-memmove.c (simple_memmove): Disable loop transformation
> 	to library calls.
> 	* string/test-memset.c (simple_memset): Likewise.
> 	* benchtests/bench-memmove.c (simple_memmove): Likewise.

These log entries should be concrete about what they're doing.
That is, say something like, "Define with inhibit_loop_to_libcall."

> -char *
> +libc_disable_cc_loop_to_function char *
>  simple_memset (char *s, int c, size_t n)

Put the macro on its own line, after the return-type line.
That's the style we've used for internal_function in many places.

> +dnl Check wheter the compiler may replace some loop constructions

typo: "whether"


Thanks,
Roland