[Bug target/60604] [4.9 Regression] GCC incorrectly compiles s_csinh function on MIPS32 (32bit fp)

[sje at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60604

--- Comment #7 from Steve Ellcey <sje at gcc dot gnu.org> ---
I didn't notice that just before the emit-rtl.c (validate_subregs) comment
that says:

  /* Subregs involving floating point modes are not allowed to
     change size.  Therefore (subreg:DI (reg:DF) 0) is fine, but
     (subreg:SI (reg:DF) 0) isn't.  */


Is another comment (and code) that has:

  /* ??? This should not be here.  Temporarily continue to allow word_mode
     subregs of anything.  The most common offender is (subreg:SI (reg:DF)).
     Generally, backends are doing something sketchy but it'll take time to
     fix them all.  */
  if (omode == word_mode)
    ;

This is why we are creating the 'bad' subregs.