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//===-- lib/CodeGen/PHIElimination.h ----------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_PHIELIMINATION_HPP
#define LLVM_CODEGEN_PHIELIMINATION_HPP
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Target/TargetInstrInfo.h"
#include <map>
namespace llvm {
/// Lower PHI instructions to copies.
class PHIElimination : public MachineFunctionPass {
MachineRegisterInfo *MRI; // Machine register information
public:
static char ID; // Pass identification, replacement for typeid
PHIElimination() : MachineFunctionPass(&ID) {}
virtual bool runOnMachineFunction(MachineFunction &Fn);
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
private:
/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions
/// in predecessor basic blocks.
///
bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB);
void LowerAtomicPHINode(MachineBasicBlock &MBB,
MachineBasicBlock::iterator AfterPHIsIt);
/// analyzePHINodes - Gather information about the PHI nodes in
/// here. In particular, we want to map the number of uses of a virtual
/// register which is used in a PHI node. We map that to the BB the
/// vreg is coming from. This is used later to determine when the vreg
/// is killed in the BB.
///
void analyzePHINodes(const MachineFunction& Fn);
// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from
// SrcReg. This needs to be after any def or uses of SrcReg, but before
// any subsequent point where control flow might jump out of the basic
// block.
MachineBasicBlock::iterator FindCopyInsertPoint(MachineBasicBlock &MBB,
unsigned SrcReg);
// SkipPHIsAndLabels - Copies need to be inserted after phi nodes and
// also after any exception handling labels: in landing pads execution
// starts at the label, so any copies placed before it won't be executed!
MachineBasicBlock::iterator SkipPHIsAndLabels(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
// Rather than assuming that EH labels come before other kinds of labels,
// just skip all labels.
while (I != MBB.end() &&
(I->getOpcode() == TargetInstrInfo::PHI || I->isLabel()))
++I;
return I;
}
typedef std::pair<const MachineBasicBlock*, unsigned> BBVRegPair;
typedef std::map<BBVRegPair, unsigned> VRegPHIUse;
VRegPHIUse VRegPHIUseCount;
// Defs of PHI sources which are implicit_def.
SmallPtrSet<MachineInstr*, 4> ImpDefs;
};
}
#endif /* PHIELIMINATION_H */