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      1 //===- LoopSink.h - Loop Sink Pass ------------------------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file provides the interface for the Loop Sink pass.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_TRANSFORMS_SCALAR_LOOPSINK_H
     15 #define LLVM_TRANSFORMS_SCALAR_LOOPSINK_H
     16 
     17 #include "llvm/Analysis/LoopInfo.h"
     18 #include "llvm/IR/PassManager.h"
     19 #include "llvm/Transforms/Scalar/LoopPassManager.h"
     20 
     21 namespace llvm {
     22 
     23 /// A pass that does profile-guided sinking of instructions into loops.
     24 ///
     25 /// This is a function pass as it shouldn't be composed into any kind of
     26 /// unified loop pass pipeline. The goal of it is to sink code into loops that
     27 /// is loop invariant but only required within the loop body when doing so
     28 /// reduces the global expected dynamic frequency with which it executes.
     29 /// A classic example is an extremely cold branch within a loop body.
     30 ///
     31 /// We do this as a separate pass so that during normal optimization all
     32 /// invariant operations can be held outside the loop body to simplify
     33 /// fundamental analyses and transforms of the loop.
     34 class LoopSinkPass : public PassInfoMixin<LoopSinkPass> {
     35 public:
     36   PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM);
     37 };
     38 }
     39 
     40 #endif // LLVM_TRANSFORMS_SCALAR_LOOPSINK_H
     41