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 BitVector UsedPhysRegs;
61 /// ReservedRegs - This is a bit vector of reserved registers. The target
62 /// may change its mind about which registers should be reserved. This
63 /// vector is the frozen set of reserved registers when register allocation
65 BitVector ReservedRegs;
67 /// LiveIns/LiveOuts - Keep track of the physical registers that are
68 /// livein/liveout of the function. Live in values are typically arguments in
69 /// registers, live out values are typically return values in registers.
70 /// LiveIn values are allowed to have virtual registers associated with them,
71 /// stored in the second element.
72 std::vector<std::pair<unsigned, unsigned> > LiveIns;
73 std::vector<unsigned> LiveOuts;
75 MachineRegisterInfo(const MachineRegisterInfo&); // DO NOT IMPLEMENT
76 void operator=(const MachineRegisterInfo&); // DO NOT IMPLEMENT
78 explicit MachineRegisterInfo(const TargetRegisterInfo &TRI);
79 ~MachineRegisterInfo();
81 //===--------------------------------------------------------------------===//
83 //===--------------------------------------------------------------------===//
85 // isSSA - Returns true when the machine function is in SSA form. Early
86 // passes require the machine function to be in SSA form where every virtual
87 // register has a single defining instruction.
89 // The TwoAddressInstructionPass and PHIElimination passes take the machine
90 // function out of SSA form when they introduce multiple defs per virtual
92 bool isSSA() const { return IsSSA; }
94 // leaveSSA - Indicates that the machine function is no longer in SSA form.
95 void leaveSSA() { IsSSA = false; }
97 //===--------------------------------------------------------------------===//
99 //===--------------------------------------------------------------------===//
101 /// reg_begin/reg_end - Provide iteration support to walk over all definitions
102 /// and uses of a register within the MachineFunction that corresponds to this
103 /// MachineRegisterInfo object.
104 template<bool Uses, bool Defs, bool SkipDebug>
105 class defusechain_iterator;
107 /// reg_iterator/reg_begin/reg_end - Walk all defs and uses of the specified
109 typedef defusechain_iterator<true,true,false> reg_iterator;
110 reg_iterator reg_begin(unsigned RegNo) const {
111 return reg_iterator(getRegUseDefListHead(RegNo));
113 static reg_iterator reg_end() { return reg_iterator(0); }
115 /// reg_empty - Return true if there are no instructions using or defining the
116 /// specified register (it may be live-in).
117 bool reg_empty(unsigned RegNo) const { return reg_begin(RegNo) == reg_end(); }
119 /// reg_nodbg_iterator/reg_nodbg_begin/reg_nodbg_end - Walk all defs and uses
120 /// of the specified register, skipping those marked as Debug.
121 typedef defusechain_iterator<true,true,true> reg_nodbg_iterator;
122 reg_nodbg_iterator reg_nodbg_begin(unsigned RegNo) const {
123 return reg_nodbg_iterator(getRegUseDefListHead(RegNo));
125 static reg_nodbg_iterator reg_nodbg_end() { return reg_nodbg_iterator(0); }
127 /// reg_nodbg_empty - Return true if the only instructions using or defining
128 /// Reg are Debug instructions.
129 bool reg_nodbg_empty(unsigned RegNo) const {
130 return reg_nodbg_begin(RegNo) == reg_nodbg_end();
133 /// def_iterator/def_begin/def_end - Walk all defs of the specified register.
134 typedef defusechain_iterator<false,true,false> def_iterator;
135 def_iterator def_begin(unsigned RegNo) const {
136 return def_iterator(getRegUseDefListHead(RegNo));
138 static def_iterator def_end() { return def_iterator(0); }
140 /// def_empty - Return true if there are no instructions defining the
141 /// specified register (it may be live-in).
142 bool def_empty(unsigned RegNo) const { return def_begin(RegNo) == def_end(); }
144 /// use_iterator/use_begin/use_end - Walk all uses of the specified register.
145 typedef defusechain_iterator<true,false,false> use_iterator;
146 use_iterator use_begin(unsigned RegNo) const {
147 return use_iterator(getRegUseDefListHead(RegNo));
149 static use_iterator use_end() { return use_iterator(0); }
151 /// use_empty - Return true if there are no instructions using the specified
153 bool use_empty(unsigned RegNo) const { return use_begin(RegNo) == use_end(); }
155 /// hasOneUse - Return true if there is exactly one instruction using the
156 /// specified register.
157 bool hasOneUse(unsigned RegNo) const;
159 /// use_nodbg_iterator/use_nodbg_begin/use_nodbg_end - Walk all uses of the
160 /// specified register, skipping those marked as Debug.
161 typedef defusechain_iterator<true,false,true> use_nodbg_iterator;
162 use_nodbg_iterator use_nodbg_begin(unsigned RegNo) const {
163 return use_nodbg_iterator(getRegUseDefListHead(RegNo));
165 static use_nodbg_iterator use_nodbg_end() { return use_nodbg_iterator(0); }
167 /// use_nodbg_empty - Return true if there are no non-Debug instructions
168 /// using the specified register.
169 bool use_nodbg_empty(unsigned RegNo) const {
170 return use_nodbg_begin(RegNo) == use_nodbg_end();
173 /// hasOneNonDBGUse - Return true if there is exactly one non-Debug
174 /// instruction using the specified register.
175 bool hasOneNonDBGUse(unsigned RegNo) const;
177 /// replaceRegWith - Replace all instances of FromReg with ToReg in the
178 /// machine function. This is like llvm-level X->replaceAllUsesWith(Y),
179 /// except that it also changes any definitions of the register as well.
181 /// Note that it is usually necessary to first constrain ToReg's register
182 /// class to match the FromReg constraints using:
184 /// constrainRegClass(ToReg, getRegClass(FromReg))
186 /// That function will return NULL if the virtual registers have incompatible
188 void replaceRegWith(unsigned FromReg, unsigned ToReg);
190 /// getRegUseDefListHead - Return the head pointer for the register use/def
191 /// list for the specified virtual or physical register.
192 MachineOperand *&getRegUseDefListHead(unsigned RegNo) {
193 if (TargetRegisterInfo::isVirtualRegister(RegNo))
194 return VRegInfo[RegNo].second;
195 return PhysRegUseDefLists[RegNo];
198 MachineOperand *getRegUseDefListHead(unsigned RegNo) const {
199 if (TargetRegisterInfo::isVirtualRegister(RegNo))
200 return VRegInfo[RegNo].second;
201 return PhysRegUseDefLists[RegNo];
204 /// getVRegDef - Return the machine instr that defines the specified virtual
205 /// register or null if none is found. This assumes that the code is in SSA
206 /// form, so there should only be one definition.
207 MachineInstr *getVRegDef(unsigned Reg) const;
209 /// clearKillFlags - Iterate over all the uses of the given register and
210 /// clear the kill flag from the MachineOperand. This function is used by
211 /// optimization passes which extend register lifetimes and need only
212 /// preserve conservative kill flag information.
213 void clearKillFlags(unsigned Reg) const;
216 void dumpUses(unsigned RegNo) const;
219 //===--------------------------------------------------------------------===//
220 // Virtual Register Info
221 //===--------------------------------------------------------------------===//
223 /// getRegClass - Return the register class of the specified virtual register.
225 const TargetRegisterClass *getRegClass(unsigned Reg) const {
226 return VRegInfo[Reg].first;
229 /// setRegClass - Set the register class of the specified virtual register.
231 void setRegClass(unsigned Reg, const TargetRegisterClass *RC);
233 /// constrainRegClass - Constrain the register class of the specified virtual
234 /// register to be a common subclass of RC and the current register class,
235 /// but only if the new class has at least MinNumRegs registers. Return the
236 /// new register class, or NULL if no such class exists.
237 /// This should only be used when the constraint is known to be trivial, like
238 /// GR32 -> GR32_NOSP. Beware of increasing register pressure.
240 const TargetRegisterClass *constrainRegClass(unsigned Reg,
241 const TargetRegisterClass *RC,
242 unsigned MinNumRegs = 0);
244 /// recomputeRegClass - Try to find a legal super-class of Reg's register
245 /// class that still satisfies the constraints from the instructions using
246 /// Reg. Returns true if Reg was upgraded.
248 /// This method can be used after constraints have been removed from a
249 /// virtual register, for example after removing instructions or splitting
252 bool recomputeRegClass(unsigned Reg, const TargetMachine&);
254 /// createVirtualRegister - Create and return a new virtual register in the
255 /// function with the specified register class.
257 unsigned createVirtualRegister(const TargetRegisterClass *RegClass);
259 /// getNumVirtRegs - Return the number of virtual registers created.
261 unsigned getNumVirtRegs() const { return VRegInfo.size(); }
263 /// setRegAllocationHint - Specify a register allocation hint for the
264 /// specified virtual register.
265 void setRegAllocationHint(unsigned Reg, unsigned Type, unsigned PrefReg) {
266 RegAllocHints[Reg].first = Type;
267 RegAllocHints[Reg].second = PrefReg;
270 /// getRegAllocationHint - Return the register allocation hint for the
271 /// specified virtual register.
272 std::pair<unsigned, unsigned>
273 getRegAllocationHint(unsigned Reg) const {
274 return RegAllocHints[Reg];
277 /// getSimpleHint - Return the preferred register allocation hint, or 0 if a
278 /// standard simple hint (Type == 0) is not set.
279 unsigned getSimpleHint(unsigned Reg) const {
280 std::pair<unsigned, unsigned> Hint = getRegAllocationHint(Reg);
281 return Hint.first ? 0 : Hint.second;
285 //===--------------------------------------------------------------------===//
286 // Physical Register Use Info
287 //===--------------------------------------------------------------------===//
289 /// isPhysRegUsed - Return true if the specified register is used in this
290 /// function. This only works after register allocation.
291 bool isPhysRegUsed(unsigned Reg) const { return UsedPhysRegs[Reg]; }
293 /// isPhysRegOrOverlapUsed - Return true if Reg or any overlapping register
294 /// is used in this function.
295 bool isPhysRegOrOverlapUsed(unsigned Reg) const {
296 for (const unsigned *AI = TRI->getOverlaps(Reg); *AI; ++AI)
297 if (isPhysRegUsed(*AI))
302 /// setPhysRegUsed - Mark the specified register used in this function.
303 /// This should only be called during and after register allocation.
304 void setPhysRegUsed(unsigned Reg) { UsedPhysRegs[Reg] = true; }
306 /// addPhysRegsUsed - Mark the specified registers used in this function.
307 /// This should only be called during and after register allocation.
308 void addPhysRegsUsed(const BitVector &Regs) { UsedPhysRegs |= Regs; }
310 /// setPhysRegUnused - Mark the specified register unused in this function.
311 /// This should only be called during and after register allocation.
312 void setPhysRegUnused(unsigned Reg) { UsedPhysRegs[Reg] = false; }
314 /// closePhysRegsUsed - Expand UsedPhysRegs to its transitive closure over
315 /// subregisters. That means that if R is used, so are all subregisters.
316 void closePhysRegsUsed(const TargetRegisterInfo&);
319 //===--------------------------------------------------------------------===//
320 // Reserved Register Info
321 //===--------------------------------------------------------------------===//
323 // The set of reserved registers must be invariant during register
324 // allocation. For example, the target cannot suddenly decide it needs a
325 // frame pointer when the register allocator has already used the frame
326 // pointer register for something else.
328 // These methods can be used by target hooks like hasFP() to avoid changing
329 // the reserved register set during register allocation.
331 /// freezeReservedRegs - Called by the register allocator to freeze the set
332 /// of reserved registers before allocation begins.
333 void freezeReservedRegs(const MachineFunction&);
335 /// reservedRegsFrozen - Returns true after freezeReservedRegs() was called
336 /// to ensure the set of reserved registers stays constant.
337 bool reservedRegsFrozen() const {
338 return !ReservedRegs.empty();
341 /// canReserveReg - Returns true if PhysReg can be used as a reserved
342 /// register. Any register can be reserved before freezeReservedRegs() is
344 bool canReserveReg(unsigned PhysReg) const {
345 return !reservedRegsFrozen() || ReservedRegs.test(PhysReg);
349 //===--------------------------------------------------------------------===//
350 // LiveIn/LiveOut Management
351 //===--------------------------------------------------------------------===//
353 /// addLiveIn/Out - Add the specified register as a live in/out. Note that it
354 /// is an error to add the same register to the same set more than once.
355 void addLiveIn(unsigned Reg, unsigned vreg = 0) {
356 LiveIns.push_back(std::make_pair(Reg, vreg));
358 void addLiveOut(unsigned Reg) { LiveOuts.push_back(Reg); }
360 // Iteration support for live in/out sets. These sets are kept in sorted
361 // order by their register number.
362 typedef std::vector<std::pair<unsigned,unsigned> >::const_iterator
364 typedef std::vector<unsigned>::const_iterator liveout_iterator;
365 livein_iterator livein_begin() const { return LiveIns.begin(); }
366 livein_iterator livein_end() const { return LiveIns.end(); }
367 bool livein_empty() const { return LiveIns.empty(); }
368 liveout_iterator liveout_begin() const { return LiveOuts.begin(); }
369 liveout_iterator liveout_end() const { return LiveOuts.end(); }
370 bool liveout_empty() const { return LiveOuts.empty(); }
372 bool isLiveIn(unsigned Reg) const;
373 bool isLiveOut(unsigned Reg) const;
375 /// getLiveInPhysReg - If VReg is a live-in virtual register, return the
376 /// corresponding live-in physical register.
377 unsigned getLiveInPhysReg(unsigned VReg) const;
379 /// getLiveInVirtReg - If PReg is a live-in physical register, return the
380 /// corresponding live-in physical register.
381 unsigned getLiveInVirtReg(unsigned PReg) const;
383 /// EmitLiveInCopies - Emit copies to initialize livein virtual registers
384 /// into the given entry block.
385 void EmitLiveInCopies(MachineBasicBlock *EntryMBB,
386 const TargetRegisterInfo &TRI,
387 const TargetInstrInfo &TII);
390 void HandleVRegListReallocation();
393 /// defusechain_iterator - This class provides iterator support for machine
394 /// operands in the function that use or define a specific register. If
395 /// ReturnUses is true it returns uses of registers, if ReturnDefs is true it
396 /// returns defs. If neither are true then you are silly and it always
397 /// returns end(). If SkipDebug is true it skips uses marked Debug
398 /// when incrementing.
399 template<bool ReturnUses, bool ReturnDefs, bool SkipDebug>
400 class defusechain_iterator
401 : public std::iterator<std::forward_iterator_tag, MachineInstr, ptrdiff_t> {
403 explicit defusechain_iterator(MachineOperand *op) : Op(op) {
404 // If the first node isn't one we're interested in, advance to one that
405 // we are interested in.
407 if ((!ReturnUses && op->isUse()) ||
408 (!ReturnDefs && op->isDef()) ||
409 (SkipDebug && op->isDebug()))
413 friend class MachineRegisterInfo;
415 typedef std::iterator<std::forward_iterator_tag,
416 MachineInstr, ptrdiff_t>::reference reference;
417 typedef std::iterator<std::forward_iterator_tag,
418 MachineInstr, ptrdiff_t>::pointer pointer;
420 defusechain_iterator(const defusechain_iterator &I) : Op(I.Op) {}
421 defusechain_iterator() : Op(0) {}
423 bool operator==(const defusechain_iterator &x) const {
426 bool operator!=(const defusechain_iterator &x) const {
427 return !operator==(x);
430 /// atEnd - return true if this iterator is equal to reg_end() on the value.
431 bool atEnd() const { return Op == 0; }
433 // Iterator traversal: forward iteration only
434 defusechain_iterator &operator++() { // Preincrement
435 assert(Op && "Cannot increment end iterator!");
436 Op = Op->getNextOperandForReg();
438 // If this is an operand we don't care about, skip it.
439 while (Op && ((!ReturnUses && Op->isUse()) ||
440 (!ReturnDefs && Op->isDef()) ||
441 (SkipDebug && Op->isDebug())))
442 Op = Op->getNextOperandForReg();
446 defusechain_iterator operator++(int) { // Postincrement
447 defusechain_iterator tmp = *this; ++*this; return tmp;
450 /// skipInstruction - move forward until reaching a different instruction.
451 /// Return the skipped instruction that is no longer pointed to, or NULL if
452 /// already pointing to end().
453 MachineInstr *skipInstruction() {
455 MachineInstr *MI = Op->getParent();
457 while (Op && Op->getParent() == MI);
461 MachineOperand &getOperand() const {
462 assert(Op && "Cannot dereference end iterator!");
466 /// getOperandNo - Return the operand # of this MachineOperand in its
468 unsigned getOperandNo() const {
469 assert(Op && "Cannot dereference end iterator!");
470 return Op - &Op->getParent()->getOperand(0);
473 // Retrieve a reference to the current operand.
474 MachineInstr &operator*() const {
475 assert(Op && "Cannot dereference end iterator!");
476 return *Op->getParent();
479 MachineInstr *operator->() const {
480 assert(Op && "Cannot dereference end iterator!");
481 return Op->getParent();
487 } // End llvm namespace