Chris Lattner f00b2f3fb4 Teach jump threading some more simple tricks:
1) have it fold "br undef", which does occur with
   surprising frequency as jump threading iterates.
2) teach j-t to delete dead blocks.  This removes the successor
   edges, reducing the in-edges of other blocks, allowing 
   recursive simplification.
3) Fold things like:
     br COND, BBX, BBY
  BBX:
     br COND, BBZ, BBW

   which also happens because jump threading iterates.

llvm-svn: 60470
2008-12-03 07:48:08 +00:00
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2008-11-21 20:00:59 +00:00
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