//===-- 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
// 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 "llvm/ADT/BitVector.h"
+#include "llvm/ADT/SmallVector.h"
#include <map>
namespace llvm {
class LiveVariables : public MachineFunctionPass {
public:
+ static const int ID; // Pass identifcation, replacement for typeid
+ LiveVariables() : MachineFunctionPass((intptr_t)&ID) {}
+
+ /// VarInfo - This represents the regions where a virtual register is live in
+ /// the program. We represent this with three different pieces of
+ /// information: the instruction that uniquely defines the value, the set of
+ /// blocks the instruction is live into and live out of, and the set of
+ /// non-phi instructions that are the last users of the value.
+ ///
+ /// In the common case where a value is defined and killed in the same block,
+ /// DefInst is the defining inst, there is one killing instruction, and
+ /// AliveBlocks is empty.
+ ///
+ /// Otherwise, the value is live out of the block. If the value is live
+ /// across any blocks, these blocks are listed in AliveBlocks. Blocks where
+ /// the liveness range ends are not included in AliveBlocks, instead being
+ /// captured by the Kills set. In these blocks, the value is live into the
+ /// block (unless the value is defined and killed in the same block) and lives
+ /// until the specified instruction. Note that there cannot ever be a value
+ /// whose Kills set contains two instructions from the same basic block.
+ ///
+ /// PHI nodes complicate things a bit. If a PHI node is the last user of a
+ /// value in one of its predecessor blocks, it is not listed in the kills set,
+ /// but does include the predecessor block in the AliveBlocks set (unless that
+ /// block also defines the value). This leads to the (perfectly sensical)
+ /// situation where a value is defined in a block, and the last use is a phi
+ /// node in the successor. In this case, DefInst will be the defining
+ /// instruction, AliveBlocks is empty (the value is not live across any
+ /// blocks) and Kills is empty (phi nodes are not included). This is sensical
+ /// because the value must be live to the end of the block, but is not live in
+ /// any successor blocks.
struct VarInfo {
- /// DefBlock - The basic block which defines this value...
- MachineBasicBlock *DefBlock;
- MachineInstr *DefInst;
+ /// 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;
+ BitVector AliveBlocks;
+
+ /// NumUses - Number of uses of this register across the entire function.
+ ///
+ unsigned NumUses;
- /// Kills - List of MachineBasicblock's which contain the last use of this
- /// virtual register (kill it). This also includes the specific instruction
- /// which kills the value.
+ /// Kills - List of MachineInstruction's which are the last use of this
+ /// virtual register (kill it) in their basic block.
///
- std::vector<std::pair<MachineBasicBlock*, MachineInstr*> > Kills;
+ std::vector<MachineInstr*> Kills;
- VarInfo() : DefBlock(0), DefInst(0) {}
+ VarInfo() : DefInst(0), NumUses(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<std::pair<MachineBasicBlock*, MachineInstr*> >::iterator
- i = Kills.begin(); i != Kills.end(); ++i) {
- if (i->second == 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;
}
+
+ void dump() const;
};
private:
///
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.
+ /// ReservedRegisters - This vector keeps track of which registers
+ /// are reserved register which are not allocatable by the target machine.
+ /// We can not track liveness for values that are in this set.
///
- 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;
+ BitVector ReservedRegisters;
private: // Intermediate data structures
+ MachineFunction *MF;
- /// BBMap - Maps LLVM basic blocks to their corresponding machine basic block.
- /// This also provides a numbering of the basic blocks in the function.
- std::map<const BasicBlock*, std::pair<MachineBasicBlock*, unsigned> > BBMap;
-
const MRegisterInfo *RegInfo;
+ // PhysRegInfo - Keep track of which instruction was the last def/use of a
+ // physical register. This is a purely local property, because all physical
+ // register references as presumed dead across basic blocks.
MachineInstr **PhysRegInfo;
+
+ // PhysRegUsed - Keep track whether the physical register has been used after
+ // its last definition. This is local property.
bool *PhysRegUsed;
+ // PhysRegPartUse - Keep track of which instruction was the last partial use
+ // of a physical register (e.g. on X86 a def of EAX followed by a use of AX).
+ // This is a purely local property.
+ MachineInstr **PhysRegPartUse;
+
+ // PhysRegPartDef - Keep track of a list of instructions which "partially"
+ // defined the physical register (e.g. on X86 AX partially defines EAX).
+ // These are turned into use/mod/write if there is a use of the register
+ // later in the same block. This is local property.
+ SmallVector<MachineInstr*, 4> *PhysRegPartDef;
+
+ SmallVector<unsigned, 4> *PHIVarInfo;
+
+ /// addRegisterKilled - We have determined MI kills a register. Look for the
+ /// operand that uses it and mark it as IsKill. If AddIfNotFound is true,
+ /// add a implicit operand if it's not found. Returns true if the operand
+ /// exists / is added.
+ bool addRegisterKilled(unsigned IncomingReg, MachineInstr *MI,
+ bool AddIfNotFound = false);
+
+ /// addRegisterDead - We have determined MI defined a register without a use.
+ /// Look for the operand that defines it and mark it as IsDead. If
+ /// AddIfNotFound is true, add a implicit operand if it's not found. Returns
+ /// true if the operand exists / is added.
+ bool addRegisterDead(unsigned IncomingReg, MachineInstr *MI,
+ bool AddIfNotFound = false);
+
void HandlePhysRegUse(unsigned Reg, MachineInstr *MI);
void HandlePhysRegDef(unsigned Reg, MachineInstr *MI);
+ /// analyzePHINodes - Gather information about the PHI nodes in here. In
+ /// particular, we want to map the variable information of a virtual
+ /// register which is used in a PHI node. We map that to the BB the vreg
+ /// is coming from.
+ void analyzePHINodes(const MachineFunction& Fn);
public:
virtual bool runOnMachineFunction(MachineFunction &MF);
- /// getMachineBasicBlockIndex - Turn a MachineBasicBlock into an index number
- /// suitable for use with VarInfo's.
- ///
- const std::pair<MachineBasicBlock*, unsigned>
- &getMachineBasicBlockInfo(MachineBasicBlock *MBB) const;
- const std::pair<MachineBasicBlock*, unsigned>
- &getBasicBlockInfo(const BasicBlock *BB) const {
- return BBMap.find(BB)->second;
- }
-
-
- /// killed_iterator - Iterate over registers killed by a machine instruction
- ///
- typedef std::multimap<MachineInstr*, unsigned>::iterator killed_iterator;
+ /// KillsRegister - Return true if the specified instruction kills the
+ /// specified register.
+ bool KillsRegister(MachineInstr *MI, unsigned Reg) const;
- /// 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);
- }
-
- 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);
- }
+ /// RegisterDefIsDead - Return true if the specified instruction defines the
+ /// specified register, but that definition is dead.
+ bool RegisterDefIsDead(MachineInstr *MI, unsigned Reg) const;
+ /// ModifiesRegister - Return true if the specified instruction modifies the
+ /// specified register.
+ bool ModifiesRegister(MachineInstr *MI, unsigned Reg) const;
+
//===--------------------------------------------------------------------===//
// 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,
- MachineBasicBlock *MBB,
- MachineInstr *MI) {
- RegistersKilled.insert(std::make_pair(MI, IncomingReg));
- getVarInfo(IncomingReg).Kills.push_back(std::make_pair(MBB, MI));
- }
+ /// instruction. If AddIfNotFound is true, add a implicit operand if it's
+ /// not found.
+ void addVirtualRegisterKilled(unsigned IncomingReg, MachineInstr *MI,
+ bool AddIfNotFound = false) {
+ if (addRegisterKilled(IncomingReg, MI, AddIfNotFound))
+ getVarInfo(IncomingReg).Kills.push_back(MI);
+ }
/// removeVirtualRegisterKilled - Remove the specified virtual
/// register from the live variable information. Returns true if the
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?");
+ bool Removed = false;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (MO.isReg() && MO.isUse() && MO.getReg() == reg) {
+ MO.unsetIsKill();
+ Removed = true;
+ break;
+ }
}
- RegistersKilled.erase(B, E);
+
+ assert(Removed && "Register is not used by this instruction!");
+ return true;
}
+ /// removeVirtualRegistersKilled - Remove all killed info for the specified
+ /// instruction.
+ void removeVirtualRegistersKilled(MachineInstr *MI);
+
/// addVirtualRegisterDead - Add information about the fact that the specified
- /// register is dead after being used by the specified instruction.
- ///
- void addVirtualRegisterDead(unsigned IncomingReg,
- MachineBasicBlock *MBB,
- MachineInstr *MI) {
- RegistersDead.insert(std::make_pair(MI, IncomingReg));
- getVarInfo(IncomingReg).Kills.push_back(std::make_pair(MBB, MI));
+ /// register is dead after being used by the specified instruction. If
+ /// AddIfNotFound is true, add a implicit operand if it's not found.
+ void addVirtualRegisterDead(unsigned IncomingReg, MachineInstr *MI,
+ bool AddIfNotFound = false) {
+ if (addRegisterDead(IncomingReg, MI, AddIfNotFound))
+ getVarInfo(IncomingReg).Kills.push_back(MI);
}
/// removeVirtualRegisterDead - Remove the specified virtual
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;
+ bool Removed = false;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (MO.isReg() && MO.isDef() && MO.getReg() == reg) {
+ MO.unsetIsDead();
+ Removed = true;
+ break;
+ }
}
+ assert(Removed && "Register is not defined by this instruction!");
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);
- }
-
+ /// removeVirtualRegistersDead - Remove all of the dead registers for the
+ /// specified instruction from the live variable information.
+ void removeVirtualRegistersDead(MachineInstr *MI);
+
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
virtual void releaseMemory() {
VirtRegInfo.clear();
- RegistersKilled.clear();
- RegistersDead.clear();
- BBMap.clear();
}
/// getVarInfo - Return the VarInfo structure for the specified VIRTUAL
/// register.
VarInfo &getVarInfo(unsigned RegIdx);
- const std::vector<bool>& getAllocatablePhysicalRegisters() const {
- return AllocatablePhysicalRegisters;
- }
-
- void MarkVirtRegAliveInBlock(VarInfo &VRInfo, const BasicBlock *BB);
+ void MarkVirtRegAliveInBlock(VarInfo &VRInfo, MachineBasicBlock *BB);
void HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB,
- MachineInstr *MI);
+ MachineInstr *MI);
};
} // End llvm namespace
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