Richard Sandiford 32379b8141 [SystemZ] Optimize (sext (ashr (shl ...), ...)) ...

...into (ashr (shl (anyext X), ...), ...), which requires one fewer
instruction.  The (anyext X) can sometimes be simplified too.

I didn't do this in DAGCombiner because widening shifts isn't a win
on all targets.

llvm-svn: 199114

2014-01-13 15:17:53 +00:00

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