Eliminate generality that is not buying us anything.  In particular, this will cause us to miss cases where the input pointer to a load could be value numbered to another load.  Something like this:
Eliminate generality that is not buying us anything.  In particular, this
will cause us to miss cases where the input pointer to a load could be value
numbered to another load.  Something like this:


  %X = load int* %P1
  %Y = load int* %P2

Those are obviously the same if P1/P2 are the same.  The code this patch
removes attempts to handle that.  However, since GCSE iterates, this doesn't
actually buy us anything: GCSE will first replace P1 or P2 with the other
one, then the load can be value numbered as equal.

Removing this code speeds up gcse a lot.  On 176.gcc in debug mode, this
speeds up gcse from 29.08s -> 25.73s, a 13% savings.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@19906 91177308-0d34-0410-b5e6-96231b3b80d8

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