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llvm-mirror/include/llvm/CodeGen/LiveVariables.h
Misha Brukman 5e38b1e17e Convert tabs to spaces
llvm-svn: 21438
2005-04-22 03:46:24 +00:00

252 lines
9.1 KiB
C++

//===-- llvm/CodeGen/LiveVariables.h - Live Variable Analysis ---*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LiveVariable analysis pass. For each machine
// instruction in the function, this pass calculates the set of registers that
// are immediately dead after the instruction (i.e., the instruction calculates
// the value, but it is never used) and the set of registers that are used by
// the instruction, but are never used after the instruction (i.e., they are
// killed).
//
// This class computes live variables using are sparse implementation based on
// the machine code SSA form. This class computes live variable information for
// each virtual and _register allocatable_ physical register in a function. It
// uses the dominance properties of SSA form to efficiently compute live
// variables for virtual registers, and assumes that physical registers are only
// live within a single basic block (allowing it to do a single local analysis
// to resolve physical register lifetimes in each basic block). If a physical
// register is not register allocatable, it is not tracked. This is useful for
// things like the stack pointer and condition codes.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_LIVEVARIABLES_H
#define LLVM_CODEGEN_LIVEVARIABLES_H
#include "llvm/CodeGen/MachineFunctionPass.h"
#include <map>
namespace llvm {
class MRegisterInfo;
class LiveVariables : public MachineFunctionPass {
public:
struct VarInfo {
/// DefInst - The machine instruction that defines this register.
MachineInstr *DefInst;
/// AliveBlocks - Set of blocks of which this value is alive completely
/// through. This is a bit set which uses the basic block number as an
/// index.
///
std::vector<bool> AliveBlocks;
/// Kills - List of MachineInstruction's which are the last use of this
/// virtual register (kill it) in their basic block.
///
std::vector<MachineInstr*> Kills;
VarInfo() : DefInst(0) {}
/// removeKill - Delete a kill corresponding to the specified
/// machine instruction. Returns true if there was a kill
/// corresponding to this instruction, false otherwise.
bool removeKill(MachineInstr *MI) {
for (std::vector<MachineInstr*>::iterator i = Kills.begin(),
e = Kills.end(); i != e; ++i)
if (*i == MI) {
Kills.erase(i);
return true;
}
return false;
}
};
private:
/// VirtRegInfo - This list is a mapping from virtual register number to
/// variable information. FirstVirtualRegister is subtracted from the virtual
/// register number before indexing into this list.
///
std::vector<VarInfo> VirtRegInfo;
/// RegistersKilled - This multimap keeps track of all of the registers that
/// are dead immediately after an instruction reads its operands. If an
/// instruction does not have an entry in this map, it kills no registers.
///
std::multimap<MachineInstr*, unsigned> RegistersKilled;
/// RegistersDead - This multimap keeps track of all of the registers that are
/// dead immediately after an instruction executes, which are not dead after
/// the operands are evaluated. In practice, this only contains registers
/// which are defined by an instruction, but never used.
///
std::multimap<MachineInstr*, unsigned> RegistersDead;
/// AllocatablePhysicalRegisters - This vector keeps track of which registers
/// are actually register allocatable by the target machine. We can not track
/// liveness for values that are not in this set.
///
std::vector<bool> AllocatablePhysicalRegisters;
private: // Intermediate data structures
const MRegisterInfo *RegInfo;
MachineInstr **PhysRegInfo;
bool *PhysRegUsed;
void HandlePhysRegUse(unsigned Reg, MachineInstr *MI);
void HandlePhysRegDef(unsigned Reg, MachineInstr *MI);
public:
virtual bool runOnMachineFunction(MachineFunction &MF);
/// killed_iterator - Iterate over registers killed by a machine instruction
///
typedef std::multimap<MachineInstr*, unsigned>::iterator killed_iterator;
/// killed_begin/end - Get access to the range of registers killed by a
/// machine instruction.
killed_iterator killed_begin(MachineInstr *MI) {
return RegistersKilled.lower_bound(MI);
}
killed_iterator killed_end(MachineInstr *MI) {
return RegistersKilled.upper_bound(MI);
}
std::pair<killed_iterator, killed_iterator>
killed_range(MachineInstr *MI) {
return RegistersKilled.equal_range(MI);
}
/// KillsRegister - Return true if the specified instruction kills the
/// specified register.
bool KillsRegister(MachineInstr *MI, unsigned Reg) {
std::pair<killed_iterator, killed_iterator> KIP = killed_range(MI);
for (; KIP.first != KIP.second; ++KIP.first)
if (KIP.first->second == Reg)
return true;
return false;
}
killed_iterator dead_begin(MachineInstr *MI) {
return RegistersDead.lower_bound(MI);
}
killed_iterator dead_end(MachineInstr *MI) {
return RegistersDead.upper_bound(MI);
}
std::pair<killed_iterator, killed_iterator>
dead_range(MachineInstr *MI) {
return RegistersDead.equal_range(MI);
}
//===--------------------------------------------------------------------===//
// API to update live variable information
/// instructionChanged - When the address of an instruction changes, this
/// method should be called so that live variables can update its internal
/// data structures. This removes the records for OldMI, transfering them to
/// the records for NewMI.
void instructionChanged(MachineInstr *OldMI, MachineInstr *NewMI);
/// addVirtualRegisterKilled - Add information about the fact that the
/// specified register is killed after being used by the specified
/// instruction.
///
void addVirtualRegisterKilled(unsigned IncomingReg, MachineInstr *MI) {
RegistersKilled.insert(std::make_pair(MI, IncomingReg));
getVarInfo(IncomingReg).Kills.push_back(MI);
}
/// removeVirtualRegisterKilled - Remove the specified virtual
/// register from the live variable information. Returns true if the
/// variable was marked as killed by the specified instruction,
/// false otherwise.
bool removeVirtualRegisterKilled(unsigned reg,
MachineBasicBlock *MBB,
MachineInstr *MI) {
if (!getVarInfo(reg).removeKill(MI))
return false;
for (killed_iterator i = killed_begin(MI), e = killed_end(MI); i != e; ) {
if (i->second == reg)
RegistersKilled.erase(i++);
else
++i;
}
return true;
}
/// removeVirtualRegistersKilled - Remove all of the specified killed
/// registers from the live variable information.
void removeVirtualRegistersKilled(killed_iterator B, killed_iterator E) {
for (killed_iterator I = B; I != E; ++I) { // Remove VarInfo entries...
bool removed = getVarInfo(I->second).removeKill(I->first);
assert(removed && "kill not in register's VarInfo?");
}
RegistersKilled.erase(B, E);
}
/// addVirtualRegisterDead - Add information about the fact that the specified
/// register is dead after being used by the specified instruction.
///
void addVirtualRegisterDead(unsigned IncomingReg, MachineInstr *MI) {
RegistersDead.insert(std::make_pair(MI, IncomingReg));
getVarInfo(IncomingReg).Kills.push_back(MI);
}
/// removeVirtualRegisterDead - Remove the specified virtual
/// register from the live variable information. Returns true if the
/// variable was marked dead at the specified instruction, false
/// otherwise.
bool removeVirtualRegisterDead(unsigned reg,
MachineBasicBlock *MBB,
MachineInstr *MI) {
if (!getVarInfo(reg).removeKill(MI))
return false;
for (killed_iterator i = killed_begin(MI), e = killed_end(MI); i != e; ) {
if (i->second == reg)
RegistersKilled.erase(i++);
else
++i;
}
return true;
}
/// removeVirtualRegistersDead - Remove all of the specified dead
/// registers from the live variable information.
void removeVirtualRegistersDead(killed_iterator B, killed_iterator E) {
for (killed_iterator I = B; I != E; ++I) // Remove VarInfo entries...
getVarInfo(I->second).removeKill(I->first);
RegistersDead.erase(B, E);
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
virtual void releaseMemory() {
VirtRegInfo.clear();
RegistersKilled.clear();
RegistersDead.clear();
}
/// getVarInfo - Return the VarInfo structure for the specified VIRTUAL
/// register.
VarInfo &getVarInfo(unsigned RegIdx);
void MarkVirtRegAliveInBlock(VarInfo &VRInfo, MachineBasicBlock *BB);
void HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB,
MachineInstr *MI);
};
} // End llvm namespace
#endif