When canonicalizing dags according to the rule
(shl (zext (shr X, c1) ), c1) ==> (zext (shl (shr X, c1), c1))
remember to add the new shl dag to the DAGCombiner worklist of nodes.
If we don't explicitly add it to the worklist of nodes to visit, we
may not trigger later on the rule that folds the shift left + logical
shift right into a AND instruction with bitmask.
llvm-svn: 192883
This change fixes the problem reported in pr17380 and re-add the dagcombine
transformation ensuring that the value types are always legal if the
transformation is triggered after Legalization took place.
Added the test case from pr17380.
llvm-svn: 191509
(shl (zext (shr A, X)), X) => (zext (shl (shr A, X), X)).
The rule only triggers when there are no other uses of the
zext to avoid materializing more instructions.
This helps the DAGCombiner understand that the shl/shr
sequence can then be converted into an and instruction.
llvm-svn: 191393
Andrea Di Biagio