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Author SHA1 Message Date
Adam Nemet d4e56073c7 [X86] Add peephole for masked rotate amount 
Extend what's currently done for shift because the HW performs this masking
implicitly:

   (rotl:i32 x, (and y, 31)) -> (rotl:i32 x, y)

I use the newly factored out multiclass that was only supporting shifts so
far.

For testing I extended my testcase for the new rotation idiom.

<rdar://problem/15295856>

llvm-svn: 203718
 2014-03-12 21:20:55 +00:00
Adam Nemet 4203039760 Update comment from r203315 based on review 
llvm-svn: 203361
 2014-03-08 21:51:55 +00:00
Adam Nemet 5117f5dffc [DAGCombiner] Recognize another rotation idiom 
This is the new idiom:

  x<<(y&31) | x>>((0-y)&31)

which is recognized as:

  x ROTL (y&31)

The change refines matchRotateSub.  In
Neg & (OpSize - 1) == (OpSize - Pos) & (OpSize - 1), if Pos is
Pos' & (OpSize - 1) we can just use Pos' instead of Pos.

llvm-svn: 203315
 2014-03-07 23:56:28 +00:00