79 lines
2.4 KiB
C++
79 lines
2.4 KiB
C++
//===-- LoopAligner.cpp - Loop aligner pass. ------------------------------===//
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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 file implements the pass that align loop headers to target specific
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// alignment boundary.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "loopalign"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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using namespace llvm;
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namespace {
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class LoopAligner : public MachineFunctionPass {
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public:
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static char ID;
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LoopAligner() : MachineFunctionPass(&ID) {}
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virtual bool runOnMachineFunction(MachineFunction &MF);
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virtual const char *getPassName() const { return "Loop aligner"; }
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<MachineLoopInfo>();
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AU.addPreserved<MachineLoopInfo>();
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AU.addPreservedID(MachineDominatorsID);
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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};
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char LoopAligner::ID = 0;
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} // end anonymous namespace
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FunctionPass *llvm::createLoopAlignerPass() { return new LoopAligner(); }
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bool LoopAligner::runOnMachineFunction(MachineFunction &MF) {
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const MachineLoopInfo *MLI = &getAnalysis<MachineLoopInfo>();
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if (MLI->empty())
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return false; // No loops.
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const TargetLowering *TLI = MF.getTarget().getTargetLowering();
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if (!TLI)
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return false;
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unsigned Align = TLI->getPrefLoopAlignment();
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if (!Align)
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return false; // Don't care about loop alignment.
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const Function *F = MF.getFunction();
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if (F->hasFnAttr(Attribute::OptimizeForSize))
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return false;
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
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MachineBasicBlock *MBB = I;
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if (MLI->isLoopHeader(MBB)) {
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MachineBasicBlock *PredBB = prior(I);
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if (MLI->getLoopFor(MBB) == MLI->getLoopFor(PredBB))
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// If previously BB is in the same loop, don't align this BB. We want
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// to prevent adding noop's inside a loop.
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continue;
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MBB->setAlignment(Align);
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}
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}
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return true;
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}
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