//
// 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 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
+// This file implements the LiveVariables 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
+// This class computes live variables using a 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
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
-#include <map>
namespace llvm {
-class MRegisterInfo;
+class MachineRegisterInfo;
+class TargetRegisterInfo;
class LiveVariables : public MachineFunctionPass {
public:
- static char ID; // Pass identifcation, replacement for typeid
- LiveVariables() : MachineFunctionPass((intptr_t)&ID) {}
+ static char ID; // Pass identification, replacement for typeid
+ LiveVariables() : MachineFunctionPass(&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.
+ /// information: the set of blocks in which the instruction is live
+ /// throughout, the set of blocks in which the instruction is actually used,
+ /// 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.
+ /// 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.
+ /// throughout 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.
+ /// node in the successor. In this case, 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 {
- /// DefInst - The machine instruction that defines this register.
- ///
- MachineInstr *DefInst;
-
- /// AliveBlocks - Set of blocks of which this value is alive completely
+ /// AliveBlocks - Set of blocks in which this value is alive completely
/// through. This is a bit set which uses the basic block number as an
/// index.
///
BitVector AliveBlocks;
+ /// UsedBlocks - Set of blocks in which this value is actually used. This
+ /// is a bit set which uses the basic block number as an index.
+ BitVector UsedBlocks;
+
/// NumUses - Number of uses of this register across the entire function.
///
unsigned NumUses;
///
std::vector<MachineInstr*> Kills;
- VarInfo() : DefInst(0), NumUses(0) {}
+ VarInfo() : 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<MachineInstr*>::iterator i = Kills.begin(),
- e = Kills.end(); i != e; ++i)
- if (*i == MI) {
- Kills.erase(i);
- return true;
- }
- return false;
+ std::vector<MachineInstr*>::iterator
+ I = std::find(Kills.begin(), Kills.end(), MI);
+ if (I == Kills.end())
+ return false;
+ Kills.erase(I);
+ return true;
}
void dump() const;
private: // Intermediate data structures
MachineFunction *MF;
- const MRegisterInfo *RegInfo;
+ MachineRegisterInfo* MRI;
- // 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;
+ const TargetRegisterInfo *TRI;
- // 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;
+ // PhysRegInfo - Keep track of which instruction was the last def of a
+ // physical register. This is a purely local property, because all physical
+ // register references are presumed dead across basic blocks.
+ MachineInstr **PhysRegDef;
- // 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;
+ // PhysRegInfo - Keep track of which instruction was the last use of a
+ // physical register. This is a purely local property, because all physical
+ // register references are presumed dead across basic blocks.
+ MachineInstr **PhysRegUse;
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);
+ // DistanceMap - Keep track the distance of a MI from the start of the
+ // current basic block.
+ DenseMap<MachineInstr*, unsigned> DistanceMap;
- /// 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);
+ /// HandlePhysRegKill - Add kills of Reg and its sub-registers to the
+ /// uses. Pay special attention to the sub-register uses which may come below
+ /// the last use of the whole register.
+ bool HandlePhysRegKill(unsigned Reg, MachineInstr *MI);
void HandlePhysRegUse(unsigned Reg, MachineInstr *MI);
void HandlePhysRegDef(unsigned Reg, MachineInstr *MI);
+ /// FindLastPartialDef - Return the last partial def of the specified register.
+ /// Also returns the sub-register that's defined.
+ MachineInstr *FindLastPartialDef(unsigned Reg, unsigned &PartDefReg);
+
+ /// hasRegisterUseBelow - Return true if the specified register is used after
+ /// the current instruction and before it's next definition.
+ bool hasRegisterUseBelow(unsigned Reg, MachineBasicBlock::iterator I,
+ MachineBasicBlock *MBB);
+
/// 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
virtual bool runOnMachineFunction(MachineFunction &MF);
- /// KillsRegister - Return true if the specified instruction kills the
- /// specified register.
- bool KillsRegister(MachineInstr *MI, unsigned Reg) const;
-
/// 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);
+ /// replaceKillInstruction - Update register kill info by replacing a kill
+ /// instruction with a new one.
+ void replaceKillInstruction(unsigned Reg, MachineInstr *OldMI,
+ MachineInstr *NewMI);
/// addVirtualRegisterKilled - Add information about the fact that the
/// specified register is killed after being used by the specified
/// not found.
void addVirtualRegisterKilled(unsigned IncomingReg, MachineInstr *MI,
bool AddIfNotFound = false) {
- if (addRegisterKilled(IncomingReg, MI, AddIfNotFound))
+ if (MI->addRegisterKilled(IncomingReg, TRI, AddIfNotFound))
getVarInfo(IncomingReg).Kills.push_back(MI);
- }
+ }
- /// removeVirtualRegisterKilled - Remove the specified virtual
+ /// removeVirtualRegisterKilled - Remove the specified kill of the 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) {
+ bool removeVirtualRegisterKilled(unsigned reg, MachineInstr *MI) {
if (!getVarInfo(reg).removeKill(MI))
return false;
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();
+ if (MO.isReg() && MO.isKill() && MO.getReg() == reg) {
+ MO.setIsKill(false);
Removed = true;
break;
}
/// 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. 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);
+ if (MI->addRegisterDead(IncomingReg, TRI, AddIfNotFound))
+ getVarInfo(IncomingReg).Kills.push_back(MI);
}
- /// removeVirtualRegisterDead - Remove the specified virtual
+ /// removeVirtualRegisterDead - Remove the specified kill of the 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) {
+ bool removeVirtualRegisterDead(unsigned reg, MachineInstr *MI) {
if (!getVarInfo(reg).removeKill(MI))
return 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();
+ MO.setIsDead(false);
Removed = true;
break;
}
assert(Removed && "Register is not defined by this instruction!");
return true;
}
-
- /// 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();
- }
+ void getAnalysisUsage(AnalysisUsage &AU) const;
virtual void releaseMemory() {
VirtRegInfo.clear();
/// register.
VarInfo &getVarInfo(unsigned RegIdx);
- void MarkVirtRegAliveInBlock(VarInfo &VRInfo, MachineBasicBlock *BB);
- void HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB,
+ void MarkVirtRegAliveInBlock(VarInfo& VRInfo, MachineBasicBlock* DefBlock,
+ MachineBasicBlock *BB);
+ void MarkVirtRegAliveInBlock(VarInfo& VRInfo, MachineBasicBlock* DefBlock,
+ MachineBasicBlock *BB,
+ std::vector<MachineBasicBlock*> &WorkList);
+ void HandleVirtRegDef(unsigned reg, MachineInstr *MI);
+ void HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB,
MachineInstr *MI);
};
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