Re: APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Ian Lance Taylor <ian at airs dot com>]

Kevin McBride <kevin@planetsaphire.com> writes:

> Please take notice that I am appealing my bug (number 23605) to the
> steering committee of GCC on the basis that it is a legimate
> bug/enhancement in need of a through research.  I believe that Andrew
> Pinski is trying to keep the research from occuring by means of marking
> the bug as invalid.
> 
> I am hoping that the steering committee will order a through research on
> the bug.  There are times when it might be best to have things like
> memset() inlined by the compiler itself, as outlined in my latest
> comment to the bug.

I'm sure we all look forward to receiving orders from the steering
committee.

As pinskia noted, later, in the PR, you want the
-minline-all-stringops option, which is documented.


In the meantime, I think there may be a bug here, in that memset is
open coded for the i386 at -O0.  That doesn't make sense to me; e.g.,
it prevents setting a breakpoing on memset.  This happens in this
conditional in ix86_expand_clrmem:

  if ((!optimize || optimize_size)
      && (count == 0
	  || ((count & 0x03)
	      && (!optimize_size || (count & 0x03) + (count >> 2) > 7))))
    /* do cld; stos */

This conditional dates back to here:

Tue Jan 11 16:26:47 MET 2000  Jan Hubicka <jh@suse.cz>

	...
	(cld pattern): New.
	(movstrsi, clrstr, cmpstr, strlen expander): Emit cld instruction
	(movstrsi_1, clrstrsi_1, cmpstrsi_1, strlensi_1,
	cmpstrsi_nz_1 insn): Do not output cld instruction

Any thoughts on this?

Ian