llvm-6502/include/llvm/CodeGen/MachineRegisterInfo.h
Evan Cheng 358dec5180 Part 1.
- Change register allocation hint to a pair of unsigned integers. The hint type is zero (which means prefer the register specified as second part of the pair) or entirely target dependent.
- Allow targets to specify alternative register allocation orders based on allocation hint.

Part 2.
- Use the register allocation hint system to implement more aggressive load / store multiple formation.
- Aggressively form LDRD / STRD. These are formed *before* register allocation. It has to be done this way to shorten live interval of base and offset registers. e.g.
v1025 = LDR v1024, 0
v1026 = LDR v1024, 0
=>
v1025,v1026 = LDRD v1024, 0

If this transformation isn't done before allocation, v1024 will overlap v1025 which means it more difficult to allocate a register pair.

- Even with the register allocation hint, it may not be possible to get the desired allocation. In that case, the post-allocation load / store multiple pass must fix the ldrd / strd instructions. They can either become ldm / stm instructions or back to a pair of ldr / str instructions.

This is work in progress, not yet enabled.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73381 91177308-0d34-0410-b5e6-96231b3b80d8
2009-06-15 08:28:29 +00:00

333 lines
13 KiB
C++

//===-- llvm/CodeGen/MachineRegisterInfo.h ----------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the MachineRegisterInfo class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_MACHINEREGISTERINFO_H
#define LLVM_CODEGEN_MACHINEREGISTERINFO_H
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/iterator.h"
#include <vector>
namespace llvm {
/// MachineRegisterInfo - Keep track of information for virtual and physical
/// registers, including vreg register classes, use/def chains for registers,
/// etc.
class MachineRegisterInfo {
/// VRegInfo - Information we keep for each virtual register. The entries in
/// this vector are actually converted to vreg numbers by adding the
/// TargetRegisterInfo::FirstVirtualRegister delta to their index.
///
/// Each element in this list contains the register class of the vreg and the
/// start of the use/def list for the register.
std::vector<std::pair<const TargetRegisterClass*, MachineOperand*> > VRegInfo;
/// RegClassVRegMap - This vector acts as a map from TargetRegisterClass to
/// virtual registers. For each target register class, it keeps a list of
/// virtual registers belonging to the class.
std::vector<std::vector<unsigned> > RegClass2VRegMap;
/// RegAllocHints - This vector records register allocation hints for virtual
/// registers. For each virtual register, it keeps a register and hint type
/// pair making up the allocation hint. Hint type is target specific except
/// for the value 0 which means the second value of the pair is the preferred
/// register for allocation. For example, if the hint is <0, 1024>, it means
/// the allocator should prefer the physical register allocated to the virtual
/// register of the hint.
std::vector<std::pair<unsigned, unsigned> > RegAllocHints;
/// PhysRegUseDefLists - This is an array of the head of the use/def list for
/// physical registers.
MachineOperand **PhysRegUseDefLists;
/// UsedPhysRegs - This is a bit vector that is computed and set by the
/// register allocator, and must be kept up to date by passes that run after
/// register allocation (though most don't modify this). This is used
/// so that the code generator knows which callee save registers to save and
/// for other target specific uses.
BitVector UsedPhysRegs;
/// LiveIns/LiveOuts - Keep track of the physical registers that are
/// livein/liveout of the function. Live in values are typically arguments in
/// registers, live out values are typically return values in registers.
/// LiveIn values are allowed to have virtual registers associated with them,
/// stored in the second element.
std::vector<std::pair<unsigned, unsigned> > LiveIns;
std::vector<unsigned> LiveOuts;
MachineRegisterInfo(const MachineRegisterInfo&); // DO NOT IMPLEMENT
void operator=(const MachineRegisterInfo&); // DO NOT IMPLEMENT
public:
explicit MachineRegisterInfo(const TargetRegisterInfo &TRI);
~MachineRegisterInfo();
//===--------------------------------------------------------------------===//
// Register Info
//===--------------------------------------------------------------------===//
/// reg_begin/reg_end - Provide iteration support to walk over all definitions
/// and uses of a register within the MachineFunction that corresponds to this
/// MachineRegisterInfo object.
template<bool Uses, bool Defs>
class defusechain_iterator;
/// reg_iterator/reg_begin/reg_end - Walk all defs and uses of the specified
/// register.
typedef defusechain_iterator<true,true> reg_iterator;
reg_iterator reg_begin(unsigned RegNo) const {
return reg_iterator(getRegUseDefListHead(RegNo));
}
static reg_iterator reg_end() { return reg_iterator(0); }
/// reg_empty - Return true if there are no instructions using or defining the
/// specified register (it may be live-in).
bool reg_empty(unsigned RegNo) const { return reg_begin(RegNo) == reg_end(); }
/// def_iterator/def_begin/def_end - Walk all defs of the specified register.
typedef defusechain_iterator<false,true> def_iterator;
def_iterator def_begin(unsigned RegNo) const {
return def_iterator(getRegUseDefListHead(RegNo));
}
static def_iterator def_end() { return def_iterator(0); }
/// def_empty - Return true if there are no instructions defining the
/// specified register (it may be live-in).
bool def_empty(unsigned RegNo) const { return def_begin(RegNo) == def_end(); }
/// use_iterator/use_begin/use_end - Walk all uses of the specified register.
typedef defusechain_iterator<true,false> use_iterator;
use_iterator use_begin(unsigned RegNo) const {
return use_iterator(getRegUseDefListHead(RegNo));
}
static use_iterator use_end() { return use_iterator(0); }
/// use_empty - Return true if there are no instructions using the specified
/// register.
bool use_empty(unsigned RegNo) const { return use_begin(RegNo) == use_end(); }
/// replaceRegWith - Replace all instances of FromReg with ToReg in the
/// machine function. This is like llvm-level X->replaceAllUsesWith(Y),
/// except that it also changes any definitions of the register as well.
void replaceRegWith(unsigned FromReg, unsigned ToReg);
/// getRegUseDefListHead - Return the head pointer for the register use/def
/// list for the specified virtual or physical register.
MachineOperand *&getRegUseDefListHead(unsigned RegNo) {
if (RegNo < TargetRegisterInfo::FirstVirtualRegister)
return PhysRegUseDefLists[RegNo];
RegNo -= TargetRegisterInfo::FirstVirtualRegister;
return VRegInfo[RegNo].second;
}
MachineOperand *getRegUseDefListHead(unsigned RegNo) const {
if (RegNo < TargetRegisterInfo::FirstVirtualRegister)
return PhysRegUseDefLists[RegNo];
RegNo -= TargetRegisterInfo::FirstVirtualRegister;
return VRegInfo[RegNo].second;
}
/// getVRegDef - Return the machine instr that defines the specified virtual
/// register or null if none is found. This assumes that the code is in SSA
/// form, so there should only be one definition.
MachineInstr *getVRegDef(unsigned Reg) const;
#ifndef NDEBUG
void dumpUses(unsigned RegNo) const;
#endif
//===--------------------------------------------------------------------===//
// Virtual Register Info
//===--------------------------------------------------------------------===//
/// getRegClass - Return the register class of the specified virtual register.
///
const TargetRegisterClass *getRegClass(unsigned Reg) const {
Reg -= TargetRegisterInfo::FirstVirtualRegister;
assert(Reg < VRegInfo.size() && "Invalid vreg!");
return VRegInfo[Reg].first;
}
/// setRegClass - Set the register class of the specified virtual register.
///
void setRegClass(unsigned Reg, const TargetRegisterClass *RC);
/// createVirtualRegister - Create and return a new virtual register in the
/// function with the specified register class.
///
unsigned createVirtualRegister(const TargetRegisterClass *RegClass);
/// getLastVirtReg - Return the highest currently assigned virtual register.
///
unsigned getLastVirtReg() const {
return (unsigned)VRegInfo.size()+TargetRegisterInfo::FirstVirtualRegister-1;
}
/// getRegClassVirtRegs - Return the list of virtual registers of the given
/// target register class.
std::vector<unsigned> &getRegClassVirtRegs(const TargetRegisterClass *RC) {
return RegClass2VRegMap[RC->getID()];
}
/// setRegAllocationHint - Specify a register allocation hint for the
/// specified virtual register.
void setRegAllocationHint(unsigned Reg, unsigned Type, unsigned PrefReg) {
Reg -= TargetRegisterInfo::FirstVirtualRegister;
assert(Reg < VRegInfo.size() && "Invalid vreg!");
RegAllocHints[Reg].first = Type;
RegAllocHints[Reg].second = PrefReg;
}
/// getRegAllocationHint - Return the register allocation hint for the
/// specified virtual register.
std::pair<unsigned, unsigned>
getRegAllocationHint(unsigned Reg) const {
Reg -= TargetRegisterInfo::FirstVirtualRegister;
assert(Reg < VRegInfo.size() && "Invalid vreg!");
return RegAllocHints[Reg];
}
//===--------------------------------------------------------------------===//
// Physical Register Use Info
//===--------------------------------------------------------------------===//
/// isPhysRegUsed - Return true if the specified register is used in this
/// function. This only works after register allocation.
bool isPhysRegUsed(unsigned Reg) const { return UsedPhysRegs[Reg]; }
/// setPhysRegUsed - Mark the specified register used in this function.
/// This should only be called during and after register allocation.
void setPhysRegUsed(unsigned Reg) { UsedPhysRegs[Reg] = true; }
/// setPhysRegUnused - Mark the specified register unused in this function.
/// This should only be called during and after register allocation.
void setPhysRegUnused(unsigned Reg) { UsedPhysRegs[Reg] = false; }
//===--------------------------------------------------------------------===//
// LiveIn/LiveOut Management
//===--------------------------------------------------------------------===//
/// addLiveIn/Out - Add the specified register as a live in/out. Note that it
/// is an error to add the same register to the same set more than once.
void addLiveIn(unsigned Reg, unsigned vreg = 0) {
LiveIns.push_back(std::make_pair(Reg, vreg));
}
void addLiveOut(unsigned Reg) { LiveOuts.push_back(Reg); }
// Iteration support for live in/out sets. These sets are kept in sorted
// order by their register number.
typedef std::vector<std::pair<unsigned,unsigned> >::const_iterator
livein_iterator;
typedef std::vector<unsigned>::const_iterator liveout_iterator;
livein_iterator livein_begin() const { return LiveIns.begin(); }
livein_iterator livein_end() const { return LiveIns.end(); }
bool livein_empty() const { return LiveIns.empty(); }
liveout_iterator liveout_begin() const { return LiveOuts.begin(); }
liveout_iterator liveout_end() const { return LiveOuts.end(); }
bool liveout_empty() const { return LiveOuts.empty(); }
bool isLiveIn(unsigned Reg) const {
for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
if (I->first == Reg || I->second == Reg)
return true;
return false;
}
private:
void HandleVRegListReallocation();
public:
/// defusechain_iterator - This class provides iterator support for machine
/// operands in the function that use or define a specific register. If
/// ReturnUses is true it returns uses of registers, if ReturnDefs is true it
/// returns defs. If neither are true then you are silly and it always
/// returns end().
template<bool ReturnUses, bool ReturnDefs>
class defusechain_iterator
: public forward_iterator<MachineInstr, ptrdiff_t> {
MachineOperand *Op;
explicit defusechain_iterator(MachineOperand *op) : Op(op) {
// If the first node isn't one we're interested in, advance to one that
// we are interested in.
if (op) {
if ((!ReturnUses && op->isUse()) ||
(!ReturnDefs && op->isDef()))
++*this;
}
}
friend class MachineRegisterInfo;
public:
typedef forward_iterator<MachineInstr, ptrdiff_t>::reference reference;
typedef forward_iterator<MachineInstr, ptrdiff_t>::pointer pointer;
defusechain_iterator(const defusechain_iterator &I) : Op(I.Op) {}
defusechain_iterator() : Op(0) {}
bool operator==(const defusechain_iterator &x) const {
return Op == x.Op;
}
bool operator!=(const defusechain_iterator &x) const {
return !operator==(x);
}
/// atEnd - return true if this iterator is equal to reg_end() on the value.
bool atEnd() const { return Op == 0; }
// Iterator traversal: forward iteration only
defusechain_iterator &operator++() { // Preincrement
assert(Op && "Cannot increment end iterator!");
Op = Op->getNextOperandForReg();
// If this is an operand we don't care about, skip it.
while (Op && ((!ReturnUses && Op->isUse()) ||
(!ReturnDefs && Op->isDef())))
Op = Op->getNextOperandForReg();
return *this;
}
defusechain_iterator operator++(int) { // Postincrement
defusechain_iterator tmp = *this; ++*this; return tmp;
}
MachineOperand &getOperand() const {
assert(Op && "Cannot dereference end iterator!");
return *Op;
}
/// getOperandNo - Return the operand # of this MachineOperand in its
/// MachineInstr.
unsigned getOperandNo() const {
assert(Op && "Cannot dereference end iterator!");
return Op - &Op->getParent()->getOperand(0);
}
// Retrieve a reference to the current operand.
MachineInstr &operator*() const {
assert(Op && "Cannot dereference end iterator!");
return *Op->getParent();
}
MachineInstr *operator->() const {
assert(Op && "Cannot dereference end iterator!");
return Op->getParent();
}
};
};
} // End llvm namespace
#endif