Re: PowerPC shrink-wrap support 3 of 3

[Bernd Schmidt <bernds@codesourcery.com>]

On 10/26/11 14:27, Alan Modra wrote:
> Committed revision 180522.  It turns out that shrink-wrapping isn't as
> effective as it used to be with the 20110915 based sources I was using
> originally.  povray Ray_In_Bound no longer gets the benefit of shrink
> wrap, likely due to some cfg optimization.  We end up with a simple
> block that just does r3=1 then jumps to last_bb being reached from
> blocks that need a prologue as well as blocks that don't.  That's
> enough to kill our current shrink wrap implementation.  What we need
> is something to duplicate these tail blocks..

Would it work to insert the epilogue on some edges to this R3=1 block,
and not on the others? (How many edges of each kind are there?)

Now that we have an initial patch in the tree and it mostly seems to
work, we can think about making it a little stronger - the initial
implementation is really quite conservative.


Bernd