Re: [tree-ssa] COND_EXPR lowering preview

[Jason Merrill <jason at redhat dot com>]

On Wed, 27 Aug 2003 14:21:10 -0600, law@redhat.com wrote:

> In message <20030827201640.GA13443@atrey.karlin.mff.cuni.cz>, Zdenek Dvorak wri
> tes:
>  >Hello,
>  >
>  >> > I don't see the value in having it separate.  All that does is force 
>  >> > another walk over the statements, which seems awful wasteful.  I'd
>  >> > prefer to see this lowering happen during gimplification.
>  >> > 
>  >> We are going to be doing separate lowering pass with EH.  We can
>  >> piggyback all the lowering code in there.
>  >> 
>  >> The reason I tend to prefer this is more stylistic than anything else. 
>  >> The only example I had in mind was code analysis.  The purist in me
>  >> would like to have a clean separation between GIMPLE as an IL and the
>  >> lowering of GIMPLE to benefit our scalar optimizers.  Since we are
>  >> already going to do a separate lowering pass, we could do it there.
>  >> 
>  >> But, as I said before, I'm not that opposed to doing it in the
>  >> gimplifier.  I don't have a strong technical reason now, so I'm happy
>  >> with what the majority thinks it's best.
>  >
>  >from "amount of work" point of view, I would slightly prefer a separate
>  >pass too.  With cond_exprs I have somehow managed to place it into
>  >gimplification (although even this was more complicated than I thought),
>  >but for switch_expr lowering, this imho would be quite cumbersome.

> Well, then let's make it separate lowering pass.

For switches, OK, but there's already code to do COND_EXPR lowering in the
gimplifier in order to handle && and || semantics.  I really don't want
two copies of that code floating around the compiler.

Jason