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[SelectionDAG] Add SRA/SHL demanded elts support to ComputeNumSignBits
authorSimon Pilgrim <llvm-dev@redking.me.uk>
Sun, 29 Oct 2017 18:19:37 +0000 (18:19 +0000)
committerSimon Pilgrim <llvm-dev@redking.me.uk>
Sun, 29 Oct 2017 18:19:37 +0000 (18:19 +0000)
commitb3d173b2690e8364b9b4b4f2823636e3ea712324
tree9736b67a38ec8c7c1e9485db7e0caa4c4a2b6796
parentefd461e3e36b6ee5019ea728451e78a633aea587
[SelectionDAG] Add SRA/SHL demanded elts support to ComputeNumSignBits

Introduce a isConstOrDemandedConstSplat helper function that can recognise a constant splat build vector for at least the demanded elts we care about.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316866 91177308-0d34-0410-b5e6-96231b3b80d8
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
test/CodeGen/X86/known-signbits-vector.ll