Patch to allow strlen expander to fail

[Jeffrey A Law]

  In message < 200003060159.e261xPj06505@sleipnir.valparaiso.cl >you write:
  > Jan Hubicka <hubicka@atrey.karlin.mff.cuni.cz> said on gcc-patches:
  > > This patch adds the strlen libcall and necesary code to emit_builtin_strl
  > en
  > > to emit libcall when strlen expander fails.
  > 
  > Is there some documentation about the functions gcc might generate calls
  > to? 
No, and any such documentation would have the caveat that the conditions
under which GCC will use a libcall can change without warning or
predictability.

Any code which depends on gcc generating or not generating libcalls is
broken.

  > There was recently a problem with the Linux kernel because gcc
  > willy-nilly called memcpy(3), and that one isn't around in the kernel,
Then that's a kernel problem.  They're depending on a specific, undocumented
and highly implementation dependent behavior in the compiler.  That's dumb.

jeff