Re: [PATCH (9/7)] Widening multiplies with constant inputs

[Andrew Stubbs <ams at codesourcery dot com>]

On 21/07/11 14:22, Richard Guenther wrote:
> On Thu, Jul 21, 2011 at 2:53 PM, Andrew Stubbs<ams@codesourcery.com>  wrote:
> > This patch is part bug fix, part better optimization.
> >
> > Firstly, my initial patch series introduced a bug that caused an internal
> > compiler error when the input to a multiply was a constant. This was caused
> > by the gimple verification rejecting such things. I'm not totally clear how
> > this ever worked, but I've corrected it by inserting a temporary SSA_NAME
> > between the constant and the multiply.
>
> Huh?  Constant operands should be perfectly fine.  What was the error
> you got?

Ok, so it seems that the fold_convert we thought was redundant in patch 
5 (now moved to patch 2) was in fact responsible for making constants 
the right type.

I've rewritten it to use fold_convert to change the constant.

> > I also discovered that widening multiply-and-accumulate operations were not
> > recognised if any one of the three inputs were a constant. I've corrected
> > this by adjusting the pattern matching. This also required inserting new
> > SSA_NAMEs to make it work.
>
> See above.

The pattern matching stuff remains the same, but the constant 
conversions have been updated.

> > In order to insert the new SSA_NAME, I've simply reused the existing type
> > conversion code - the only difference is that the conversion may be a no-op,
> > so it just generates a straight forward assignment.
> >
> > OK?
>
> Nope.  I suppose you forget to adjust the constants type?  Just
> fold-convert it before using it as input to a macc.

Done.

OK?

Andrew