Reload bug & SRA oddness

[Bernd Schmidt]

Daniel Berlin wrote:
> It would also be a mistake to try to do significant optimization of
> copy in/out placement directly in SRA.  Again, that is why we have PRE
> and DSE.  If they are not moving/eliminating these things, they need
> to be fixed.

I've had a look at why these statements are not eliminated.  I figure 
that dce is the pass that should get rid of them, but it doesn't.  From 
the dumps:

   # SFT.70_14 = VDEF <SFT.70_13(D)>
   y.k = y$k_9(D);
   # VUSE <sD_15(D)>
   # SFT.70_19 = VDEF <SFT.70_14>
   # SFT.71_20 = VDEF <SFT.71_16(D)>
   # SFT.72_21 = VDEF <SFT.72_17(D)>
   # SFT.73_22 = VDEF <SFT.73_18(D)>
   y = sD;

Note how all the VDEFs have an input argument, which causes us to 
believe that the second statement depends on the first.  AFAICT, these 
VDEFs should have no arguments, but the compiler always generates them 
with exactly one input.  I've tried to fix that, but so far the patch I 
have is only useful as an SSA learning tool for myself, as it creates 
lots of failures elsewhere in the compiler...

Any other ideas how to address this?


Bernd
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