1 //===-- llvm/CodeGen/MachineRegisterInfo.h ----------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the MachineRegisterInfo class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_MACHINEREGISTERINFO_H
15 #define LLVM_CODEGEN_MACHINEREGISTERINFO_H
17 #include "llvm/Target/TargetRegisterInfo.h"
18 #include "llvm/ADT/BitVector.h"
19 #include "llvm/ADT/IndexedMap.h"
24 /// MachineRegisterInfo - Keep track of information for virtual and physical
25 /// registers, including vreg register classes, use/def chains for registers,
27 class MachineRegisterInfo {
28 const TargetRegisterInfo *const TRI;
30 /// IsSSA - True when the machine function is in SSA form and virtual
31 /// registers have a single def.
34 /// VRegInfo - Information we keep for each virtual register.
36 /// Each element in this list contains the register class of the vreg and the
37 /// start of the use/def list for the register.
38 IndexedMap<std::pair<const TargetRegisterClass*, MachineOperand*>,
39 VirtReg2IndexFunctor> VRegInfo;
41 /// RegAllocHints - This vector records register allocation hints for virtual
42 /// registers. For each virtual register, it keeps a register and hint type
43 /// pair making up the allocation hint. Hint type is target specific except
44 /// for the value 0 which means the second value of the pair is the preferred
45 /// register for allocation. For example, if the hint is <0, 1024>, it means
46 /// the allocator should prefer the physical register allocated to the virtual
47 /// register of the hint.
48 IndexedMap<std::pair<unsigned, unsigned>, VirtReg2IndexFunctor> RegAllocHints;
50 /// PhysRegUseDefLists - This is an array of the head of the use/def list for
51 /// physical registers.
52 MachineOperand **PhysRegUseDefLists;
54 /// UsedPhysRegs - This is a bit vector that is computed and set by the
55 /// register allocator, and must be kept up to date by passes that run after
56 /// register allocation (though most don't modify this). This is used
57 /// so that the code generator knows which callee save registers to save and
58 /// for other target specific uses.
59 /// This vector only has bits set for registers explicitly used, not their
61 BitVector UsedPhysRegs;
63 /// UsedPhysRegMask - Additional used physregs, but including aliases.
64 BitVector UsedPhysRegMask;
66 /// ReservedRegs - This is a bit vector of reserved registers. The target
67 /// may change its mind about which registers should be reserved. This
68 /// vector is the frozen set of reserved registers when register allocation
70 BitVector ReservedRegs;
72 /// AllocatableRegs - From TRI->getAllocatableSet.
73 mutable BitVector AllocatableRegs;
75 /// LiveIns/LiveOuts - Keep track of the physical registers that are
76 /// livein/liveout of the function. Live in values are typically arguments in
77 /// registers, live out values are typically return values in registers.
78 /// LiveIn values are allowed to have virtual registers associated with them,
79 /// stored in the second element.
80 std::vector<std::pair<unsigned, unsigned> > LiveIns;
81 std::vector<unsigned> LiveOuts;
83 MachineRegisterInfo(const MachineRegisterInfo&); // DO NOT IMPLEMENT
84 void operator=(const MachineRegisterInfo&); // DO NOT IMPLEMENT
86 explicit MachineRegisterInfo(const TargetRegisterInfo &TRI);
87 ~MachineRegisterInfo();
89 //===--------------------------------------------------------------------===//
91 //===--------------------------------------------------------------------===//
93 // isSSA - Returns true when the machine function is in SSA form. Early
94 // passes require the machine function to be in SSA form where every virtual
95 // register has a single defining instruction.
97 // The TwoAddressInstructionPass and PHIElimination passes take the machine
98 // function out of SSA form when they introduce multiple defs per virtual
100 bool isSSA() const { return IsSSA; }
102 // leaveSSA - Indicates that the machine function is no longer in SSA form.
103 void leaveSSA() { IsSSA = false; }
105 //===--------------------------------------------------------------------===//
107 //===--------------------------------------------------------------------===//
109 /// reg_begin/reg_end - Provide iteration support to walk over all definitions
110 /// and uses of a register within the MachineFunction that corresponds to this
111 /// MachineRegisterInfo object.
112 template<bool Uses, bool Defs, bool SkipDebug>
113 class defusechain_iterator;
115 /// reg_iterator/reg_begin/reg_end - Walk all defs and uses of the specified
117 typedef defusechain_iterator<true,true,false> reg_iterator;
118 reg_iterator reg_begin(unsigned RegNo) const {
119 return reg_iterator(getRegUseDefListHead(RegNo));
121 static reg_iterator reg_end() { return reg_iterator(0); }
123 /// reg_empty - Return true if there are no instructions using or defining the
124 /// specified register (it may be live-in).
125 bool reg_empty(unsigned RegNo) const { return reg_begin(RegNo) == reg_end(); }
127 /// reg_nodbg_iterator/reg_nodbg_begin/reg_nodbg_end - Walk all defs and uses
128 /// of the specified register, skipping those marked as Debug.
129 typedef defusechain_iterator<true,true,true> reg_nodbg_iterator;
130 reg_nodbg_iterator reg_nodbg_begin(unsigned RegNo) const {
131 return reg_nodbg_iterator(getRegUseDefListHead(RegNo));
133 static reg_nodbg_iterator reg_nodbg_end() { return reg_nodbg_iterator(0); }
135 /// reg_nodbg_empty - Return true if the only instructions using or defining
136 /// Reg are Debug instructions.
137 bool reg_nodbg_empty(unsigned RegNo) const {
138 return reg_nodbg_begin(RegNo) == reg_nodbg_end();
141 /// def_iterator/def_begin/def_end - Walk all defs of the specified register.
142 typedef defusechain_iterator<false,true,false> def_iterator;
143 def_iterator def_begin(unsigned RegNo) const {
144 return def_iterator(getRegUseDefListHead(RegNo));
146 static def_iterator def_end() { return def_iterator(0); }
148 /// def_empty - Return true if there are no instructions defining the
149 /// specified register (it may be live-in).
150 bool def_empty(unsigned RegNo) const { return def_begin(RegNo) == def_end(); }
152 /// use_iterator/use_begin/use_end - Walk all uses of the specified register.
153 typedef defusechain_iterator<true,false,false> use_iterator;
154 use_iterator use_begin(unsigned RegNo) const {
155 return use_iterator(getRegUseDefListHead(RegNo));
157 static use_iterator use_end() { return use_iterator(0); }
159 /// use_empty - Return true if there are no instructions using the specified
161 bool use_empty(unsigned RegNo) const { return use_begin(RegNo) == use_end(); }
163 /// hasOneUse - Return true if there is exactly one instruction using the
164 /// specified register.
165 bool hasOneUse(unsigned RegNo) const;
167 /// use_nodbg_iterator/use_nodbg_begin/use_nodbg_end - Walk all uses of the
168 /// specified register, skipping those marked as Debug.
169 typedef defusechain_iterator<true,false,true> use_nodbg_iterator;
170 use_nodbg_iterator use_nodbg_begin(unsigned RegNo) const {
171 return use_nodbg_iterator(getRegUseDefListHead(RegNo));
173 static use_nodbg_iterator use_nodbg_end() { return use_nodbg_iterator(0); }
175 /// use_nodbg_empty - Return true if there are no non-Debug instructions
176 /// using the specified register.
177 bool use_nodbg_empty(unsigned RegNo) const {
178 return use_nodbg_begin(RegNo) == use_nodbg_end();
181 /// hasOneNonDBGUse - Return true if there is exactly one non-Debug
182 /// instruction using the specified register.
183 bool hasOneNonDBGUse(unsigned RegNo) const;
185 /// replaceRegWith - Replace all instances of FromReg with ToReg in the
186 /// machine function. This is like llvm-level X->replaceAllUsesWith(Y),
187 /// except that it also changes any definitions of the register as well.
189 /// Note that it is usually necessary to first constrain ToReg's register
190 /// class to match the FromReg constraints using:
192 /// constrainRegClass(ToReg, getRegClass(FromReg))
194 /// That function will return NULL if the virtual registers have incompatible
196 void replaceRegWith(unsigned FromReg, unsigned ToReg);
198 /// getRegUseDefListHead - Return the head pointer for the register use/def
199 /// list for the specified virtual or physical register.
200 MachineOperand *&getRegUseDefListHead(unsigned RegNo) {
201 if (TargetRegisterInfo::isVirtualRegister(RegNo))
202 return VRegInfo[RegNo].second;
203 return PhysRegUseDefLists[RegNo];
206 MachineOperand *getRegUseDefListHead(unsigned RegNo) const {
207 if (TargetRegisterInfo::isVirtualRegister(RegNo))
208 return VRegInfo[RegNo].second;
209 return PhysRegUseDefLists[RegNo];
212 /// getVRegDef - Return the machine instr that defines the specified virtual
213 /// register or null if none is found. This assumes that the code is in SSA
214 /// form, so there should only be one definition.
215 MachineInstr *getVRegDef(unsigned Reg) const;
217 /// clearKillFlags - Iterate over all the uses of the given register and
218 /// clear the kill flag from the MachineOperand. This function is used by
219 /// optimization passes which extend register lifetimes and need only
220 /// preserve conservative kill flag information.
221 void clearKillFlags(unsigned Reg) const;
224 void dumpUses(unsigned RegNo) const;
227 /// isConstantPhysReg - Returns true if PhysReg is unallocatable and constant
228 /// throughout the function. It is safe to move instructions that read such
230 bool isConstantPhysReg(unsigned PhysReg, const MachineFunction &MF) const;
232 //===--------------------------------------------------------------------===//
233 // Virtual Register Info
234 //===--------------------------------------------------------------------===//
236 /// getRegClass - Return the register class of the specified virtual register.
238 const TargetRegisterClass *getRegClass(unsigned Reg) const {
239 return VRegInfo[Reg].first;
242 /// setRegClass - Set the register class of the specified virtual register.
244 void setRegClass(unsigned Reg, const TargetRegisterClass *RC);
246 /// constrainRegClass - Constrain the register class of the specified virtual
247 /// register to be a common subclass of RC and the current register class,
248 /// but only if the new class has at least MinNumRegs registers. Return the
249 /// new register class, or NULL if no such class exists.
250 /// This should only be used when the constraint is known to be trivial, like
251 /// GR32 -> GR32_NOSP. Beware of increasing register pressure.
253 const TargetRegisterClass *constrainRegClass(unsigned Reg,
254 const TargetRegisterClass *RC,
255 unsigned MinNumRegs = 0);
257 /// recomputeRegClass - Try to find a legal super-class of Reg's register
258 /// class that still satisfies the constraints from the instructions using
259 /// Reg. Returns true if Reg was upgraded.
261 /// This method can be used after constraints have been removed from a
262 /// virtual register, for example after removing instructions or splitting
265 bool recomputeRegClass(unsigned Reg, const TargetMachine&);
267 /// createVirtualRegister - Create and return a new virtual register in the
268 /// function with the specified register class.
270 unsigned createVirtualRegister(const TargetRegisterClass *RegClass);
272 /// getNumVirtRegs - Return the number of virtual registers created.
274 unsigned getNumVirtRegs() const { return VRegInfo.size(); }
276 /// setRegAllocationHint - Specify a register allocation hint for the
277 /// specified virtual register.
278 void setRegAllocationHint(unsigned Reg, unsigned Type, unsigned PrefReg) {
279 RegAllocHints[Reg].first = Type;
280 RegAllocHints[Reg].second = PrefReg;
283 /// getRegAllocationHint - Return the register allocation hint for the
284 /// specified virtual register.
285 std::pair<unsigned, unsigned>
286 getRegAllocationHint(unsigned Reg) const {
287 return RegAllocHints[Reg];
290 /// getSimpleHint - Return the preferred register allocation hint, or 0 if a
291 /// standard simple hint (Type == 0) is not set.
292 unsigned getSimpleHint(unsigned Reg) const {
293 std::pair<unsigned, unsigned> Hint = getRegAllocationHint(Reg);
294 return Hint.first ? 0 : Hint.second;
298 //===--------------------------------------------------------------------===//
299 // Physical Register Use Info
300 //===--------------------------------------------------------------------===//
302 /// isPhysRegUsed - Return true if the specified register is used in this
303 /// function. This only works after register allocation.
304 bool isPhysRegUsed(unsigned Reg) const {
305 return UsedPhysRegs.test(Reg) || UsedPhysRegMask.test(Reg);
308 /// isPhysRegOrOverlapUsed - Return true if Reg or any overlapping register
309 /// is used in this function.
310 bool isPhysRegOrOverlapUsed(unsigned Reg) const {
311 if (UsedPhysRegMask.test(Reg))
313 for (const unsigned *AI = TRI->getOverlaps(Reg); *AI; ++AI)
314 if (UsedPhysRegs.test(*AI))
319 /// setPhysRegUsed - Mark the specified register used in this function.
320 /// This should only be called during and after register allocation.
321 void setPhysRegUsed(unsigned Reg) { UsedPhysRegs.set(Reg); }
323 /// addPhysRegsUsed - Mark the specified registers used in this function.
324 /// This should only be called during and after register allocation.
325 void addPhysRegsUsed(const BitVector &Regs) { UsedPhysRegs |= Regs; }
327 /// addPhysRegsUsedFromRegMask - Mark any registers not in RegMask as used.
328 /// This corresponds to the bit mask attached to register mask operands.
329 void addPhysRegsUsedFromRegMask(const uint32_t *RegMask) {
330 UsedPhysRegMask.setBitsNotInMask(RegMask);
333 /// setPhysRegUnused - Mark the specified register unused in this function.
334 /// This should only be called during and after register allocation.
335 void setPhysRegUnused(unsigned Reg) {
336 UsedPhysRegs.reset(Reg);
337 UsedPhysRegMask.reset(Reg);
341 //===--------------------------------------------------------------------===//
342 // Reserved Register Info
343 //===--------------------------------------------------------------------===//
345 // The set of reserved registers must be invariant during register
346 // allocation. For example, the target cannot suddenly decide it needs a
347 // frame pointer when the register allocator has already used the frame
348 // pointer register for something else.
350 // These methods can be used by target hooks like hasFP() to avoid changing
351 // the reserved register set during register allocation.
353 /// freezeReservedRegs - Called by the register allocator to freeze the set
354 /// of reserved registers before allocation begins.
355 void freezeReservedRegs(const MachineFunction&);
357 /// reservedRegsFrozen - Returns true after freezeReservedRegs() was called
358 /// to ensure the set of reserved registers stays constant.
359 bool reservedRegsFrozen() const {
360 return !ReservedRegs.empty();
363 /// canReserveReg - Returns true if PhysReg can be used as a reserved
364 /// register. Any register can be reserved before freezeReservedRegs() is
366 bool canReserveReg(unsigned PhysReg) const {
367 return !reservedRegsFrozen() || ReservedRegs.test(PhysReg);
371 //===--------------------------------------------------------------------===//
372 // LiveIn/LiveOut Management
373 //===--------------------------------------------------------------------===//
375 /// addLiveIn/Out - Add the specified register as a live in/out. Note that it
376 /// is an error to add the same register to the same set more than once.
377 void addLiveIn(unsigned Reg, unsigned vreg = 0) {
378 LiveIns.push_back(std::make_pair(Reg, vreg));
380 void addLiveOut(unsigned Reg) { LiveOuts.push_back(Reg); }
382 // Iteration support for live in/out sets. These sets are kept in sorted
383 // order by their register number.
384 typedef std::vector<std::pair<unsigned,unsigned> >::const_iterator
386 typedef std::vector<unsigned>::const_iterator liveout_iterator;
387 livein_iterator livein_begin() const { return LiveIns.begin(); }
388 livein_iterator livein_end() const { return LiveIns.end(); }
389 bool livein_empty() const { return LiveIns.empty(); }
390 liveout_iterator liveout_begin() const { return LiveOuts.begin(); }
391 liveout_iterator liveout_end() const { return LiveOuts.end(); }
392 bool liveout_empty() const { return LiveOuts.empty(); }
394 bool isLiveIn(unsigned Reg) const;
395 bool isLiveOut(unsigned Reg) const;
397 /// getLiveInPhysReg - If VReg is a live-in virtual register, return the
398 /// corresponding live-in physical register.
399 unsigned getLiveInPhysReg(unsigned VReg) const;
401 /// getLiveInVirtReg - If PReg is a live-in physical register, return the
402 /// corresponding live-in physical register.
403 unsigned getLiveInVirtReg(unsigned PReg) const;
405 /// EmitLiveInCopies - Emit copies to initialize livein virtual registers
406 /// into the given entry block.
407 void EmitLiveInCopies(MachineBasicBlock *EntryMBB,
408 const TargetRegisterInfo &TRI,
409 const TargetInstrInfo &TII);
412 void HandleVRegListReallocation();
415 /// defusechain_iterator - This class provides iterator support for machine
416 /// operands in the function that use or define a specific register. If
417 /// ReturnUses is true it returns uses of registers, if ReturnDefs is true it
418 /// returns defs. If neither are true then you are silly and it always
419 /// returns end(). If SkipDebug is true it skips uses marked Debug
420 /// when incrementing.
421 template<bool ReturnUses, bool ReturnDefs, bool SkipDebug>
422 class defusechain_iterator
423 : public std::iterator<std::forward_iterator_tag, MachineInstr, ptrdiff_t> {
425 explicit defusechain_iterator(MachineOperand *op) : Op(op) {
426 // If the first node isn't one we're interested in, advance to one that
427 // we are interested in.
429 if ((!ReturnUses && op->isUse()) ||
430 (!ReturnDefs && op->isDef()) ||
431 (SkipDebug && op->isDebug()))
435 friend class MachineRegisterInfo;
437 typedef std::iterator<std::forward_iterator_tag,
438 MachineInstr, ptrdiff_t>::reference reference;
439 typedef std::iterator<std::forward_iterator_tag,
440 MachineInstr, ptrdiff_t>::pointer pointer;
442 defusechain_iterator(const defusechain_iterator &I) : Op(I.Op) {}
443 defusechain_iterator() : Op(0) {}
445 bool operator==(const defusechain_iterator &x) const {
448 bool operator!=(const defusechain_iterator &x) const {
449 return !operator==(x);
452 /// atEnd - return true if this iterator is equal to reg_end() on the value.
453 bool atEnd() const { return Op == 0; }
455 // Iterator traversal: forward iteration only
456 defusechain_iterator &operator++() { // Preincrement
457 assert(Op && "Cannot increment end iterator!");
458 Op = Op->getNextOperandForReg();
460 // If this is an operand we don't care about, skip it.
461 while (Op && ((!ReturnUses && Op->isUse()) ||
462 (!ReturnDefs && Op->isDef()) ||
463 (SkipDebug && Op->isDebug())))
464 Op = Op->getNextOperandForReg();
468 defusechain_iterator operator++(int) { // Postincrement
469 defusechain_iterator tmp = *this; ++*this; return tmp;
472 /// skipInstruction - move forward until reaching a different instruction.
473 /// Return the skipped instruction that is no longer pointed to, or NULL if
474 /// already pointing to end().
475 MachineInstr *skipInstruction() {
477 MachineInstr *MI = Op->getParent();
479 while (Op && Op->getParent() == MI);
483 MachineOperand &getOperand() const {
484 assert(Op && "Cannot dereference end iterator!");
488 /// getOperandNo - Return the operand # of this MachineOperand in its
490 unsigned getOperandNo() const {
491 assert(Op && "Cannot dereference end iterator!");
492 return Op - &Op->getParent()->getOperand(0);
495 // Retrieve a reference to the current operand.
496 MachineInstr &operator*() const {
497 assert(Op && "Cannot dereference end iterator!");
498 return *Op->getParent();
501 MachineInstr *operator->() const {
502 assert(Op && "Cannot dereference end iterator!");
503 return Op->getParent();
509 } // End llvm namespace