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Re: [tree-ssa] COND_EXPR lowering preview

In message <>, Diego Novillo wr
 >On Tue, 2003-08-26 at 14:53, Zdenek Dvorak wrote:
 >> It disables control structures removal in dce; this also has to be
 >> handled separately.
 >What does this have to do with COND_EXPR lowering?
A lot actually.  If you have lowered COND_EXPRs, then there is very little
value in tracking control dependencies in DCE.

 >> It removes linearization from cfg cleanup, since the half of it
 >> is redundant with the patch and the rest contains several
 >> serious bugs (the most important one being that it uses merge_blocks; this
 >> function contains more bugs than correct code :-(
 >Test cases?  Better yet.  Fixes?  Generalizations like this one are
 >hardly useful.
As for cfg cleanup, I'd really like to see some analysis on both the
bugs and with/without.  ie, I don't want to start taking steps backwards
in terms of performance.  Simply claiming its unncessary isn't enough.

Similarly for merge blocks.  Analysis please.

 >> Some possibly useful cleanups were removed from
 >> remove_useless_stmts_and_vars; this function is not suitable for
 >> work over unstructured code.
 >Again.  Please separate this.  It has little to do with COND_EXPR
Actually remove_useless_stmts_and_vars is supposed to work with unstructured
code.  If it does not, I'd really like to see some analysis why.

 >> COND_EXPR lowering is being done in gimplification; if you like/dislike
 >> it, cry -- I personally have no opinion whether it should be done there
 >> or somewhere later.
 >I still think we should separate this from the gimplifier.  We should
 >probably have a single lowering pass that runs immediately before we
 >build the flow graph.
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.


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