Re: Patch: disable invalid REG_EQUAL note

[Andrew Pinski <pinskia at physics dot uc dot edu>]

On Apr 29, 2004, at 20:55, Dale Johannesen wrote:

> This addresses a bug that shows up building perlbmk (SPEC) in LNO 
> branch.
> cse pastes together the high and low parts of
>
>  (CONST (MINUS (LABEL_REF) (0)))
>
> each valid in context, into a REG_EQUAL; this propagates into the RHS 
> of an
> assignment without being validated, and since it is not in fact valid, 
> an ICE results.
> There's already a case where a similar pasting is disallowed, so I'd 
> like to add
> this one.  (I don't know why it happens only in LNO branch.)
> (It seems obvious to approach this instead by getting rid of the 
> redundant MINUS 0,
> but that turns out to lead into some very dusty twisty little passages 
> of the
> darwin-specific address generation code.)  Bootstrapped and tested on 
> darwin.
>
> 2004-04-29  Dale Johannesen  <dalej@apple.com>
>
>         * cse.c (cse_insn): Disallow construction of
>         (CONST (MINUS (LABEL_REF) (0))) in a REG_EQUAL note.

The only thing I could see what is wrong with this is the call to 
rtx_equal_p to
see if the rtx is zero as constants are always shared and are always 
the same so a
simple equals will be fine here (and for speed it is better as 
rtx_equal_p has a semi
large epilogue especially for checking to see if something is equal to 
a constant).

Thanks,
Andrew Pinski