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3248675f42
This is a simple implementation of the unroll-and-jam classical loop
optimisation.
The basic idea is that we take an outer loop of the form:
for i..
ForeBlocks(i)
for j..
SubLoopBlocks(i, j)
AftBlocks(i)
Instead of doing normal inner or outer unrolling, we unroll as follows:
for i... i+=2
ForeBlocks(i)
ForeBlocks(i+1)
for j..
SubLoopBlocks(i, j)
SubLoopBlocks(i+1, j)
AftBlocks(i)
AftBlocks(i+1)
Remainder Loop
So we have unrolled the outer loop, then jammed the two inner loops into
one. This can lead to a simpler inner loop if memory accesses can be shared
between the now jammed loops.
To do this we have to prove that this is all safe, both for the memory
accesses (using dependence analysis) and that ForeBlocks(i+1) can move before
AftBlocks(i) and SubLoopBlocks(i, j).
Differential Revision: https://reviews.llvm.org/D41953
llvm-svn: 336062
36 lines
1.1 KiB
C++
36 lines
1.1 KiB
C++
//===- LoopUnrollAndJamPass.h -----------------------------------*- 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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#ifndef LLVM_TRANSFORMS_SCALAR_LOOPUNROLLANDJAMPASS_H
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#define LLVM_TRANSFORMS_SCALAR_LOOPUNROLLANDJAMPASS_H
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#include "llvm/Analysis/LoopAnalysisManager.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/IR/PassManager.h"
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namespace llvm {
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class Loop;
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struct LoopStandardAnalysisResults;
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class LPMUpdater;
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/// A simple loop rotation transformation.
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class LoopUnrollAndJamPass : public PassInfoMixin<LoopUnrollAndJamPass> {
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const int OptLevel;
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public:
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explicit LoopUnrollAndJamPass(int OptLevel = 2) : OptLevel(OptLevel) {}
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PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM,
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LoopStandardAnalysisResults &AR, LPMUpdater &U);
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_SCALAR_LOOPUNROLLANDJAMPASS_H
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