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8e46796ab9
One exception here is LoopInfo which must forward-declare it (because the typedef is in LoopPassManager.h which depends on LoopInfo). Also, some includes for LoopPassManager.h were needed since that file provides the typedef. Besides a general consistently benefit, the extra layer of indirection allows the mechanical part of https://reviews.llvm.org/D23256 that requires touching every transformation and analysis to be factored out cleanly. Thanks to David for the suggestion. llvm-svn: 278079
50 lines
2.2 KiB
C++
50 lines
2.2 KiB
C++
//===- LICM.h - Loop Invariant Code Motion Pass -------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass performs loop invariant code motion, attempting to remove as much
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// code from the body of a loop as possible. It does this by either hoisting
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// code into the preheader block, or by sinking code to the exit blocks if it is
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// safe. This pass also promotes must-aliased memory locations in the loop to
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// live in registers, thus hoisting and sinking "invariant" loads and stores.
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//
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// This pass uses alias analysis for two purposes:
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//
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// 1. Moving loop invariant loads and calls out of loops. If we can determine
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// that a load or call inside of a loop never aliases anything stored to,
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// we can hoist it or sink it like any other instruction.
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// 2. Scalar Promotion of Memory - If there is a store instruction inside of
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// the loop, we try to move the store to happen AFTER the loop instead of
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// inside of the loop. This can only happen if a few conditions are true:
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// A. The pointer stored through is loop invariant
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// B. There are no stores or loads in the loop which _may_ alias the
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// pointer. There are no calls in the loop which mod/ref the pointer.
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// If these conditions are true, we can promote the loads and stores in the
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// loop of the pointer to use a temporary alloca'd variable. We then use
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// the SSAUpdater to construct the appropriate SSA form for the value.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_SCALAR_LICM_H
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#define LLVM_TRANSFORMS_SCALAR_LICM_H
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/LoopPassManager.h"
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#include "llvm/IR/PassManager.h"
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namespace llvm {
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/// Performs Loop Invariant Code Motion Pass.
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class LICMPass : public PassInfoMixin<LICMPass> {
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public:
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PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM);
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_SCALAR_LICM_H
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