Optimized Cmm containing useless blocks

Johan Tibell johan.tibell at gmail.com
Mon Mar 10 08:13:20 UTC 2014

On Sun, Mar 9, 2014 at 10:22 PM, Jan Stolarek <jan.stolarek at p.lodz.pl>wrote:

> > useless basic blocks that haven't been optimized away. Is this to be
> > expected?
> I believe this should not happen but it's hard to say without looking at a
> complete dump. Could
> you post full Cmm dump + a minimial working example that generates that?
> > On a related note, doesn't Cmm support fall-through branches?
> Cmm program is represented as a graph with each node (a block of code)
> having explicit list of
> successors. Having fall-throughs in Cmm would require storing blocks
> linearily with a guarantee
> that their order will not change. Note that fall-throughs are present in
> the generated assembly.

This was me being stupid. GHC happily prints optimized Cmm even if no
optimization was done due to a missing flag (cause GHC defaults to -O0).
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