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Avoid double branch / conditional move for promoted cttz
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Authored by dotdash on Apr 26 2015, 1:24 PM.
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Summary

Instead of handling the zero case for that promoted value and then
adjusting the result for the original type, we can set the appropriate
bit in the promoted value.

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dotdash updated this revision to Diff 24447.Apr 26 2015, 1:24 PM
dotdash retitled this revision from to Avoid double branch / conditional move for promoted cttz.
dotdash updated this object.
dotdash edited the test plan for this revision. (Show Details)
dotdash added a subscriber: Unknown Object (MLST).

Looks good, but there's room for a minor improvement still - see inline comment.

lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
4051

Another trick that can be added here: operation can now be safely changed to CTTZ_UNDEF.