If we have a clamp pattern, SMIN(SMAX(X, LO),HI) or SMAX(SMIN(X, HI),LO) then we can deduce that the number of signbits (zeros/ones) will be at least the minimum of the LO and HI constants.
ComputeKnownBits equivalent of D43338.
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| Differential D43463
[SelectionDAG] ComputeKnownBits - add support for SMIN+SMAX clamp patterns ClosedPublic Authored by RKSimon on Feb 19 2018, 6:51 AM.
Details Summary If we have a clamp pattern, SMIN(SMAX(X, LO),HI) or SMAX(SMIN(X, HI),LO) then we can deduce that the number of signbits (zeros/ones) will be at least the minimum of the LO and HI constants. ComputeKnownBits equivalent of D43338.
Diff Detail
Event TimelineThis revision is now accepted and ready to land.Feb 19 2018, 9:27 AM Closed by commit rL325521: [SelectionDAG] ComputeKnownBits - add support for SMIN+SMAX clamp patterns (authored by RKSimon). · Explain WhyFeb 19 2018, 10:10 AM This revision was automatically updated to reflect the committed changes.
Revision Contents
Diff 134905 lib/CodeGen/SelectionDAG/SelectionDAG.cpp
test/CodeGen/X86/vector-trunc-packus.ll
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