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Loop unswitching can be extremely harmful for a SIMT target. In case if hoisted condition is not uniform a SIMT machine will execute both clones of a loop sequentially. Therefor LoopUnswitch checks if the condition is non-divergent. Since DivergenceAnalysis adds an expensive PostDominatorTree analysis not needed for non-SIMT targets a new option is added to avoid unneded analysis initialization. The method getAnalysisUsage is called when TargetTransformInfo is not yet available and we cannot use it here. For that reason a new field DivergentTarget is added to PassManagerBuilder to control the behavior and set this field from a target. Differential Revision: https://reviews.llvm.org/D30796 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298104 91177308-0d34-0410-b5e6-96231b3b80d8