[PATCH] bb-reorder: Remove a misfiring micro-optimization (PR96475)

Jeff Law law@redhat.com
Tue Aug 25 20:39:56 GMT 2020


On Fri, 2020-08-07 at 21:51 +0000, Segher Boessenkool wrote:
> When the compgotos pass copies the tail of blocks ending in an indirect
> jump, there is a micro-optimization to not copy the last one, since the
> original block will then just be deleted.  This does not work properly
> if cleanup_cfg does not merge all pairs of blocks we expect it to.
> 
> 
> v2: This also deletes the other use of single_pred_p, which has the same
> problem in principle, I just never have triggered it so far.
> 
> Tested on powerpc64-linux {-m32,-m64} like before.  Is this okay for
> trunk?
> 
> 
> Segher
> 
> 
> 2020-08-07  Segher Boessenkool  <segher@kernel.crashing.org>
> 
> 	PR rtl-optimization/96475
> 	* bb-reorder.c (maybe_duplicate_computed_goto): Remove single_pred_p
> 	micro-optimization.
So this may have already been answered, but why didn't we merge the single pred
with its single succ?

Though I guess your patch wouldn't hurt, so OK.

jeff




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