mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-10-21 12:02:58 +02:00
0e35152dbe
Like several other loop passes (the vectorizer, etc) this pass doesn't really fit the model of a loop pass. The critical distinction is that it isn't intended to be pipelined together with other loop passes. I plan to add some documentation to the loop pass manager to make this more clear on that side. LoopSink is also different because it doesn't really need a lot of the infrastructure of our loop passes. For example, if there aren't loop invariant instructions causing a preheader to exist, there is no need to form a preheader. It also doesn't need LCSSA because this pass is only involved in sinking invariant instructions from a preheader into the loop, not reasoning about live-outs. This allows some nice simplifications to the pass in the new PM where we can directly walk the loops once without restructuring them. Differential Revision: https://reviews.llvm.org/D28921 llvm-svn: 292589
41 lines
1.5 KiB
C++
41 lines
1.5 KiB
C++
//===- LoopSink.h - Loop Sink Pass ------------------------------*- C++ -*-===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file provides the interface for the Loop Sink pass.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_TRANSFORMS_SCALAR_LOOPSINK_H
|
|
#define LLVM_TRANSFORMS_SCALAR_LOOPSINK_H
|
|
|
|
#include "llvm/Analysis/LoopInfo.h"
|
|
#include "llvm/IR/PassManager.h"
|
|
#include "llvm/Transforms/Scalar/LoopPassManager.h"
|
|
|
|
namespace llvm {
|
|
|
|
/// A pass that does profile-guided sinking of instructions into loops.
|
|
///
|
|
/// This is a function pass as it shouldn't be composed into any kind of
|
|
/// unified loop pass pipeline. The goal of it is to sink code into loops that
|
|
/// is loop invariant but only required within the loop body when doing so
|
|
/// reduces the global expected dynamic frequency with which it executes.
|
|
/// A classic example is an extremely cold branch within a loop body.
|
|
///
|
|
/// We do this as a separate pass so that during normal optimization all
|
|
/// invariant operations can be held outside the loop body to simplify
|
|
/// fundamental analyses and transforms of the loop.
|
|
class LoopSinkPass : public PassInfoMixin<LoopSinkPass> {
|
|
public:
|
|
PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM);
|
|
};
|
|
}
|
|
|
|
#endif // LLVM_TRANSFORMS_SCALAR_LOOPSINK_H
|