1 //=== Target/TargetRegisterInfo.h - Target Register Information -*- 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 describes an abstract interface used to get information about a
11 // target machines register file. This information is used for a variety of
12 // purposed, especially register allocation.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_TARGET_TARGETREGISTERINFO_H
17 #define LLVM_TARGET_TARGETREGISTERINFO_H
19 #include "llvm/ADT/ArrayRef.h"
20 #include "llvm/CodeGen/MachineBasicBlock.h"
21 #include "llvm/CodeGen/MachineValueType.h"
22 #include "llvm/IR/CallingConv.h"
23 #include "llvm/MC/MCRegisterInfo.h"
30 class MachineFunction;
32 template<class T> class SmallVectorImpl;
36 class TargetRegisterClass {
38 typedef const MCPhysReg* iterator;
39 typedef const MCPhysReg* const_iterator;
40 typedef const MVT::SimpleValueType* vt_iterator;
41 typedef const TargetRegisterClass* const * sc_iterator;
43 // Instance variables filled by tablegen, do not use!
44 const MCRegisterClass *MC;
45 const vt_iterator VTs;
46 const uint32_t *SubClassMask;
47 const uint16_t *SuperRegIndices;
48 const unsigned LaneMask;
49 /// Classes with a higher priority value are assigned first by register
50 /// allocators using a greedy heuristic. The value is in the range [0,63].
51 const uint8_t AllocationPriority;
52 /// Whether the class supports two (or more) disjunct subregister indices.
53 const bool HasDisjunctSubRegs;
54 const sc_iterator SuperClasses;
55 ArrayRef<MCPhysReg> (*OrderFunc)(const MachineFunction&);
57 /// getID() - Return the register class ID number.
59 unsigned getID() const { return MC->getID(); }
61 /// begin/end - Return all of the registers in this class.
63 iterator begin() const { return MC->begin(); }
64 iterator end() const { return MC->end(); }
66 /// getNumRegs - Return the number of registers in this class.
68 unsigned getNumRegs() const { return MC->getNumRegs(); }
70 /// getRegister - Return the specified register in the class.
72 unsigned getRegister(unsigned i) const {
73 return MC->getRegister(i);
76 /// contains - Return true if the specified register is included in this
77 /// register class. This does not include virtual registers.
78 bool contains(unsigned Reg) const {
79 return MC->contains(Reg);
82 /// contains - Return true if both registers are in this class.
83 bool contains(unsigned Reg1, unsigned Reg2) const {
84 return MC->contains(Reg1, Reg2);
87 /// getSize - Return the size of the register in bytes, which is also the size
88 /// of a stack slot allocated to hold a spilled copy of this register.
89 unsigned getSize() const { return MC->getSize(); }
91 /// getAlignment - Return the minimum required alignment for a register of
93 unsigned getAlignment() const { return MC->getAlignment(); }
95 /// getCopyCost - Return the cost of copying a value between two registers in
96 /// this class. A negative number means the register class is very expensive
97 /// to copy e.g. status flag register classes.
98 int getCopyCost() const { return MC->getCopyCost(); }
100 /// isAllocatable - Return true if this register class may be used to create
101 /// virtual registers.
102 bool isAllocatable() const { return MC->isAllocatable(); }
104 /// hasType - return true if this TargetRegisterClass has the ValueType vt.
106 bool hasType(MVT vt) const {
107 for(int i = 0; VTs[i] != MVT::Other; ++i)
108 if (MVT(VTs[i]) == vt)
113 /// vt_begin / vt_end - Loop over all of the value types that can be
114 /// represented by values in this register class.
115 vt_iterator vt_begin() const {
119 vt_iterator vt_end() const {
121 while (*I != MVT::Other) ++I;
125 /// hasSubClass - return true if the specified TargetRegisterClass
126 /// is a proper sub-class of this TargetRegisterClass.
127 bool hasSubClass(const TargetRegisterClass *RC) const {
128 return RC != this && hasSubClassEq(RC);
131 /// hasSubClassEq - Returns true if RC is a sub-class of or equal to this
133 bool hasSubClassEq(const TargetRegisterClass *RC) const {
134 unsigned ID = RC->getID();
135 return (SubClassMask[ID / 32] >> (ID % 32)) & 1;
138 /// hasSuperClass - return true if the specified TargetRegisterClass is a
139 /// proper super-class of this TargetRegisterClass.
140 bool hasSuperClass(const TargetRegisterClass *RC) const {
141 return RC->hasSubClass(this);
144 /// hasSuperClassEq - Returns true if RC is a super-class of or equal to this
146 bool hasSuperClassEq(const TargetRegisterClass *RC) const {
147 return RC->hasSubClassEq(this);
150 /// getSubClassMask - Returns a bit vector of subclasses, including this one.
151 /// The vector is indexed by class IDs, see hasSubClassEq() above for how to
153 const uint32_t *getSubClassMask() const {
157 /// getSuperRegIndices - Returns a 0-terminated list of sub-register indices
158 /// that project some super-register class into this register class. The list
159 /// has an entry for each Idx such that:
161 /// There exists SuperRC where:
162 /// For all Reg in SuperRC:
163 /// this->contains(Reg:Idx)
165 const uint16_t *getSuperRegIndices() const {
166 return SuperRegIndices;
169 /// getSuperClasses - Returns a NULL terminated list of super-classes. The
170 /// classes are ordered by ID which is also a topological ordering from large
171 /// to small classes. The list does NOT include the current class.
172 sc_iterator getSuperClasses() const {
176 /// isASubClass - return true if this TargetRegisterClass is a subset
177 /// class of at least one other TargetRegisterClass.
178 bool isASubClass() const {
179 return SuperClasses[0] != nullptr;
182 /// getRawAllocationOrder - Returns the preferred order for allocating
183 /// registers from this register class in MF. The raw order comes directly
184 /// from the .td file and may include reserved registers that are not
185 /// allocatable. Register allocators should also make sure to allocate
186 /// callee-saved registers only after all the volatiles are used. The
187 /// RegisterClassInfo class provides filtered allocation orders with
188 /// callee-saved registers moved to the end.
190 /// The MachineFunction argument can be used to tune the allocatable
191 /// registers based on the characteristics of the function, subtarget, or
194 /// By default, this method returns all registers in the class.
196 ArrayRef<MCPhysReg> getRawAllocationOrder(const MachineFunction &MF) const {
197 return OrderFunc ? OrderFunc(MF) : makeArrayRef(begin(), getNumRegs());
200 /// Returns the combination of all lane masks of register in this class.
201 /// The lane masks of the registers are the combination of all lane masks
202 /// of their subregisters.
203 unsigned getLaneMask() const {
208 /// TargetRegisterInfoDesc - Extra information, not in MCRegisterDesc, about
209 /// registers. These are used by codegen, not by MC.
210 struct TargetRegisterInfoDesc {
211 unsigned CostPerUse; // Extra cost of instructions using register.
212 bool inAllocatableClass; // Register belongs to an allocatable regclass.
215 /// Each TargetRegisterClass has a per register weight, and weight
216 /// limit which must be less than the limits of its pressure sets.
217 struct RegClassWeight {
219 unsigned WeightLimit;
222 /// TargetRegisterInfo base class - We assume that the target defines a static
223 /// array of TargetRegisterDesc objects that represent all of the machine
224 /// registers that the target has. As such, we simply have to track a pointer
225 /// to this array so that we can turn register number into a register
228 class TargetRegisterInfo : public MCRegisterInfo {
230 typedef const TargetRegisterClass * const * regclass_iterator;
232 const TargetRegisterInfoDesc *InfoDesc; // Extra desc array for codegen
233 const char *const *SubRegIndexNames; // Names of subreg indexes.
234 // Pointer to array of lane masks, one per sub-reg index.
235 const unsigned *SubRegIndexLaneMasks;
237 regclass_iterator RegClassBegin, RegClassEnd; // List of regclasses
238 unsigned CoveringLanes;
241 TargetRegisterInfo(const TargetRegisterInfoDesc *ID,
242 regclass_iterator RegClassBegin,
243 regclass_iterator RegClassEnd,
244 const char *const *SRINames,
245 const unsigned *SRILaneMasks,
246 unsigned CoveringLanes);
247 virtual ~TargetRegisterInfo();
250 // Register numbers can represent physical registers, virtual registers, and
251 // sometimes stack slots. The unsigned values are divided into these ranges:
253 // 0 Not a register, can be used as a sentinel.
254 // [1;2^30) Physical registers assigned by TableGen.
255 // [2^30;2^31) Stack slots. (Rarely used.)
256 // [2^31;2^32) Virtual registers assigned by MachineRegisterInfo.
258 // Further sentinels can be allocated from the small negative integers.
259 // DenseMapInfo<unsigned> uses -1u and -2u.
261 /// isStackSlot - Sometimes it is useful the be able to store a non-negative
262 /// frame index in a variable that normally holds a register. isStackSlot()
263 /// returns true if Reg is in the range used for stack slots.
265 /// Note that isVirtualRegister() and isPhysicalRegister() cannot handle stack
266 /// slots, so if a variable may contains a stack slot, always check
267 /// isStackSlot() first.
269 static bool isStackSlot(unsigned Reg) {
270 return int(Reg) >= (1 << 30);
273 /// stackSlot2Index - Compute the frame index from a register value
274 /// representing a stack slot.
275 static int stackSlot2Index(unsigned Reg) {
276 assert(isStackSlot(Reg) && "Not a stack slot");
277 return int(Reg - (1u << 30));
280 /// index2StackSlot - Convert a non-negative frame index to a stack slot
282 static unsigned index2StackSlot(int FI) {
283 assert(FI >= 0 && "Cannot hold a negative frame index.");
284 return FI + (1u << 30);
287 /// isPhysicalRegister - Return true if the specified register number is in
288 /// the physical register namespace.
289 static bool isPhysicalRegister(unsigned Reg) {
290 assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
294 /// isVirtualRegister - Return true if the specified register number is in
295 /// the virtual register namespace.
296 static bool isVirtualRegister(unsigned Reg) {
297 assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
301 /// virtReg2Index - Convert a virtual register number to a 0-based index.
302 /// The first virtual register in a function will get the index 0.
303 static unsigned virtReg2Index(unsigned Reg) {
304 assert(isVirtualRegister(Reg) && "Not a virtual register");
305 return Reg & ~(1u << 31);
308 /// index2VirtReg - Convert a 0-based index to a virtual register number.
309 /// This is the inverse operation of VirtReg2IndexFunctor below.
310 static unsigned index2VirtReg(unsigned Index) {
311 return Index | (1u << 31);
314 /// getMinimalPhysRegClass - Returns the Register Class of a physical
315 /// register of the given type, picking the most sub register class of
316 /// the right type that contains this physreg.
317 const TargetRegisterClass *
318 getMinimalPhysRegClass(unsigned Reg, MVT VT = MVT::Other) const;
320 /// getAllocatableClass - Return the maximal subclass of the given register
321 /// class that is alloctable, or NULL.
322 const TargetRegisterClass *
323 getAllocatableClass(const TargetRegisterClass *RC) const;
325 /// getAllocatableSet - Returns a bitset indexed by register number
326 /// indicating if a register is allocatable or not. If a register class is
327 /// specified, returns the subset for the class.
328 BitVector getAllocatableSet(const MachineFunction &MF,
329 const TargetRegisterClass *RC = nullptr) const;
331 /// getCostPerUse - Return the additional cost of using this register instead
332 /// of other registers in its class.
333 unsigned getCostPerUse(unsigned RegNo) const {
334 return InfoDesc[RegNo].CostPerUse;
337 /// isInAllocatableClass - Return true if the register is in the allocation
338 /// of any register class.
339 bool isInAllocatableClass(unsigned RegNo) const {
340 return InfoDesc[RegNo].inAllocatableClass;
343 /// getSubRegIndexName - Return the human-readable symbolic target-specific
344 /// name for the specified SubRegIndex.
345 const char *getSubRegIndexName(unsigned SubIdx) const {
346 assert(SubIdx && SubIdx < getNumSubRegIndices() &&
347 "This is not a subregister index");
348 return SubRegIndexNames[SubIdx-1];
351 /// getSubRegIndexLaneMask - Return a bitmask representing the parts of a
352 /// register that are covered by SubIdx.
354 /// Lane masks for sub-register indices are similar to register units for
355 /// physical registers. The individual bits in a lane mask can't be assigned
356 /// any specific meaning. They can be used to check if two sub-register
359 /// If the target has a register such that:
361 /// getSubReg(Reg, A) overlaps getSubReg(Reg, B)
365 /// (getSubRegIndexLaneMask(A) & getSubRegIndexLaneMask(B)) != 0
367 /// The converse is not necessarily true. If two lane masks have a common
368 /// bit, the corresponding sub-registers may not overlap, but it can be
369 /// assumed that they usually will.
370 /// SubIdx == 0 is allowed, it has the lane mask ~0u.
371 unsigned getSubRegIndexLaneMask(unsigned SubIdx) const {
372 assert(SubIdx < getNumSubRegIndices() && "This is not a subregister index");
373 return SubRegIndexLaneMasks[SubIdx];
376 /// Returns true if the given lane mask is imprecise.
378 /// LaneMasks as given by getSubRegIndexLaneMask() have a limited number of
379 /// bits, so for targets with more than 31 disjunct subregister indices there
380 /// may be cases where:
381 /// getSubReg(Reg,A) does not overlap getSubReg(Reg,B)
382 /// but we still have
383 /// (getSubRegIndexLaneMask(A) & getSubRegIndexLaneMask(B)) != 0.
384 /// This function returns true in those cases.
385 static bool isImpreciseLaneMask(unsigned LaneMask) {
386 return LaneMask & 0x80000000u;
389 /// The lane masks returned by getSubRegIndexLaneMask() above can only be
390 /// used to determine if sub-registers overlap - they can't be used to
391 /// determine if a set of sub-registers completely cover another
394 /// The X86 general purpose registers have two lanes corresponding to the
395 /// sub_8bit and sub_8bit_hi sub-registers. Both sub_32bit and sub_16bit have
396 /// lane masks '3', but the sub_16bit sub-register doesn't fully cover the
397 /// sub_32bit sub-register.
399 /// On the other hand, the ARM NEON lanes fully cover their registers: The
400 /// dsub_0 sub-register is completely covered by the ssub_0 and ssub_1 lanes.
401 /// This is related to the CoveredBySubRegs property on register definitions.
403 /// This function returns a bit mask of lanes that completely cover their
404 /// sub-registers. More precisely, given:
406 /// Covering = getCoveringLanes();
407 /// MaskA = getSubRegIndexLaneMask(SubA);
408 /// MaskB = getSubRegIndexLaneMask(SubB);
410 /// If (MaskA & ~(MaskB & Covering)) == 0, then SubA is completely covered by
412 unsigned getCoveringLanes() const { return CoveringLanes; }
414 /// regsOverlap - Returns true if the two registers are equal or alias each
415 /// other. The registers may be virtual register.
416 bool regsOverlap(unsigned regA, unsigned regB) const {
417 if (regA == regB) return true;
418 if (isVirtualRegister(regA) || isVirtualRegister(regB))
421 // Regunits are numerically ordered. Find a common unit.
422 MCRegUnitIterator RUA(regA, this);
423 MCRegUnitIterator RUB(regB, this);
425 if (*RUA == *RUB) return true;
426 if (*RUA < *RUB) ++RUA;
428 } while (RUA.isValid() && RUB.isValid());
432 /// hasRegUnit - Returns true if Reg contains RegUnit.
433 bool hasRegUnit(unsigned Reg, unsigned RegUnit) const {
434 for (MCRegUnitIterator Units(Reg, this); Units.isValid(); ++Units)
435 if (*Units == RegUnit)
440 /// getCalleeSavedRegs - Return a null-terminated list of all of the
441 /// callee saved registers on this target. The register should be in the
442 /// order of desired callee-save stack frame offset. The first register is
443 /// closest to the incoming stack pointer if stack grows down, and vice versa.
445 virtual const MCPhysReg*
446 getCalleeSavedRegs(const MachineFunction *MF) const = 0;
448 /// getCallPreservedMask - Return a mask of call-preserved registers for the
449 /// given calling convention on the current function. The mask should
450 /// include all call-preserved aliases. This is used by the register
451 /// allocator to determine which registers can be live across a call.
453 /// The mask is an array containing (TRI::getNumRegs()+31)/32 entries.
454 /// A set bit indicates that all bits of the corresponding register are
455 /// preserved across the function call. The bit mask is expected to be
456 /// sub-register complete, i.e. if A is preserved, so are all its
459 /// Bits are numbered from the LSB, so the bit for physical register Reg can
460 /// be found as (Mask[Reg / 32] >> Reg % 32) & 1.
462 /// A NULL pointer means that no register mask will be used, and call
463 /// instructions should use implicit-def operands to indicate call clobbered
466 virtual const uint32_t *getCallPreservedMask(const MachineFunction &MF,
467 CallingConv::ID) const {
468 // The default mask clobbers everything. All targets should override.
472 /// Return all the call-preserved register masks defined for this target.
473 virtual ArrayRef<const uint32_t *> getRegMasks() const = 0;
474 virtual ArrayRef<const char *> getRegMaskNames() const = 0;
476 /// getReservedRegs - Returns a bitset indexed by physical register number
477 /// indicating if a register is a special register that has particular uses
478 /// and should be considered unavailable at all times, e.g. SP, RA. This is
479 /// used by register scavenger to determine what registers are free.
480 virtual BitVector getReservedRegs(const MachineFunction &MF) const = 0;
482 /// Prior to adding the live-out mask to a stackmap or patchpoint
483 /// instruction, provide the target the opportunity to adjust it (mainly to
484 /// remove pseudo-registers that should be ignored).
485 virtual void adjustStackMapLiveOutMask(uint32_t *Mask) const { }
487 /// getMatchingSuperReg - Return a super-register of the specified register
488 /// Reg so its sub-register of index SubIdx is Reg.
489 unsigned getMatchingSuperReg(unsigned Reg, unsigned SubIdx,
490 const TargetRegisterClass *RC) const {
491 return MCRegisterInfo::getMatchingSuperReg(Reg, SubIdx, RC->MC);
494 /// getMatchingSuperRegClass - Return a subclass of the specified register
495 /// class A so that each register in it has a sub-register of the
496 /// specified sub-register index which is in the specified register class B.
498 /// TableGen will synthesize missing A sub-classes.
499 virtual const TargetRegisterClass *
500 getMatchingSuperRegClass(const TargetRegisterClass *A,
501 const TargetRegisterClass *B, unsigned Idx) const;
503 /// getSubClassWithSubReg - Returns the largest legal sub-class of RC that
504 /// supports the sub-register index Idx.
505 /// If no such sub-class exists, return NULL.
506 /// If all registers in RC already have an Idx sub-register, return RC.
508 /// TableGen generates a version of this function that is good enough in most
509 /// cases. Targets can override if they have constraints that TableGen
510 /// doesn't understand. For example, the x86 sub_8bit sub-register index is
511 /// supported by the full GR32 register class in 64-bit mode, but only by the
512 /// GR32_ABCD regiister class in 32-bit mode.
514 /// TableGen will synthesize missing RC sub-classes.
515 virtual const TargetRegisterClass *
516 getSubClassWithSubReg(const TargetRegisterClass *RC, unsigned Idx) const {
517 assert(Idx == 0 && "Target has no sub-registers");
521 /// composeSubRegIndices - Return the subregister index you get from composing
522 /// two subregister indices.
524 /// The special null sub-register index composes as the identity.
526 /// If R:a:b is the same register as R:c, then composeSubRegIndices(a, b)
527 /// returns c. Note that composeSubRegIndices does not tell you about illegal
528 /// compositions. If R does not have a subreg a, or R:a does not have a subreg
529 /// b, composeSubRegIndices doesn't tell you.
531 /// The ARM register Q0 has two D subregs dsub_0:D0 and dsub_1:D1. It also has
532 /// ssub_0:S0 - ssub_3:S3 subregs.
533 /// If you compose subreg indices dsub_1, ssub_0 you get ssub_2.
535 unsigned composeSubRegIndices(unsigned a, unsigned b) const {
538 return composeSubRegIndicesImpl(a, b);
541 /// Transforms a LaneMask computed for one subregister to the lanemask that
542 /// would have been computed when composing the subsubregisters with IdxA
543 /// first. @sa composeSubRegIndices()
544 unsigned composeSubRegIndexLaneMask(unsigned IdxA, unsigned LaneMask) const {
547 return composeSubRegIndexLaneMaskImpl(IdxA, LaneMask);
550 /// Debugging helper: dump register in human readable form to dbgs() stream.
551 static void dumpReg(unsigned Reg, unsigned SubRegIndex = 0,
552 const TargetRegisterInfo* TRI = nullptr);
555 /// Overridden by TableGen in targets that have sub-registers.
556 virtual unsigned composeSubRegIndicesImpl(unsigned, unsigned) const {
557 llvm_unreachable("Target has no sub-registers");
560 /// Overridden by TableGen in targets that have sub-registers.
562 composeSubRegIndexLaneMaskImpl(unsigned, unsigned) const {
563 llvm_unreachable("Target has no sub-registers");
567 /// getCommonSuperRegClass - Find a common super-register class if it exists.
569 /// Find a register class, SuperRC and two sub-register indices, PreA and
572 /// 1. PreA + SubA == PreB + SubB (using composeSubRegIndices()), and
574 /// 2. For all Reg in SuperRC: Reg:PreA in RCA and Reg:PreB in RCB, and
576 /// 3. SuperRC->getSize() >= max(RCA->getSize(), RCB->getSize()).
578 /// SuperRC will be chosen such that no super-class of SuperRC satisfies the
579 /// requirements, and there is no register class with a smaller spill size
580 /// that satisfies the requirements.
582 /// SubA and SubB must not be 0. Use getMatchingSuperRegClass() instead.
584 /// Either of the PreA and PreB sub-register indices may be returned as 0. In
585 /// that case, the returned register class will be a sub-class of the
586 /// corresponding argument register class.
588 /// The function returns NULL if no register class can be found.
590 const TargetRegisterClass*
591 getCommonSuperRegClass(const TargetRegisterClass *RCA, unsigned SubA,
592 const TargetRegisterClass *RCB, unsigned SubB,
593 unsigned &PreA, unsigned &PreB) const;
595 //===--------------------------------------------------------------------===//
596 // Register Class Information
599 /// Register class iterators
601 regclass_iterator regclass_begin() const { return RegClassBegin; }
602 regclass_iterator regclass_end() const { return RegClassEnd; }
604 unsigned getNumRegClasses() const {
605 return (unsigned)(regclass_end()-regclass_begin());
608 /// getRegClass - Returns the register class associated with the enumeration
609 /// value. See class MCOperandInfo.
610 const TargetRegisterClass *getRegClass(unsigned i) const {
611 assert(i < getNumRegClasses() && "Register Class ID out of range");
612 return RegClassBegin[i];
615 /// getRegClassName - Returns the name of the register class.
616 const char *getRegClassName(const TargetRegisterClass *Class) const {
617 return MCRegisterInfo::getRegClassName(Class->MC);
620 /// getCommonSubClass - find the largest common subclass of A and B. Return
621 /// NULL if there is no common subclass.
622 const TargetRegisterClass *
623 getCommonSubClass(const TargetRegisterClass *A,
624 const TargetRegisterClass *B) const;
626 /// getPointerRegClass - Returns a TargetRegisterClass used for pointer
627 /// values. If a target supports multiple different pointer register classes,
628 /// kind specifies which one is indicated.
629 virtual const TargetRegisterClass *
630 getPointerRegClass(const MachineFunction &MF, unsigned Kind=0) const {
631 llvm_unreachable("Target didn't implement getPointerRegClass!");
634 /// getCrossCopyRegClass - Returns a legal register class to copy a register
635 /// in the specified class to or from. If it is possible to copy the register
636 /// directly without using a cross register class copy, return the specified
637 /// RC. Returns NULL if it is not possible to copy between a two registers of
638 /// the specified class.
639 virtual const TargetRegisterClass *
640 getCrossCopyRegClass(const TargetRegisterClass *RC) const {
644 /// getLargestLegalSuperClass - Returns the largest super class of RC that is
645 /// legal to use in the current sub-target and has the same spill size.
646 /// The returned register class can be used to create virtual registers which
647 /// means that all its registers can be copied and spilled.
648 virtual const TargetRegisterClass *
649 getLargestLegalSuperClass(const TargetRegisterClass *RC,
650 const MachineFunction &) const {
651 /// The default implementation is very conservative and doesn't allow the
652 /// register allocator to inflate register classes.
656 /// getRegPressureLimit - Return the register pressure "high water mark" for
657 /// the specific register class. The scheduler is in high register pressure
658 /// mode (for the specific register class) if it goes over the limit.
660 /// Note: this is the old register pressure model that relies on a manually
661 /// specified representative register class per value type.
662 virtual unsigned getRegPressureLimit(const TargetRegisterClass *RC,
663 MachineFunction &MF) const {
667 /// Get the weight in units of pressure for this register class.
668 virtual const RegClassWeight &getRegClassWeight(
669 const TargetRegisterClass *RC) const = 0;
671 /// Get the weight in units of pressure for this register unit.
672 virtual unsigned getRegUnitWeight(unsigned RegUnit) const = 0;
674 /// Get the number of dimensions of register pressure.
675 virtual unsigned getNumRegPressureSets() const = 0;
677 /// Get the name of this register unit pressure set.
678 virtual const char *getRegPressureSetName(unsigned Idx) const = 0;
680 /// Get the register unit pressure limit for this dimension.
681 /// This limit must be adjusted dynamically for reserved registers.
682 virtual unsigned getRegPressureSetLimit(const MachineFunction &MF,
683 unsigned Idx) const = 0;
685 /// Get the dimensions of register pressure impacted by this register class.
686 /// Returns a -1 terminated array of pressure set IDs.
687 virtual const int *getRegClassPressureSets(
688 const TargetRegisterClass *RC) const = 0;
690 /// Get the dimensions of register pressure impacted by this register unit.
691 /// Returns a -1 terminated array of pressure set IDs.
692 virtual const int *getRegUnitPressureSets(unsigned RegUnit) const = 0;
694 /// Get a list of 'hint' registers that the register allocator should try
695 /// first when allocating a physical register for the virtual register
696 /// VirtReg. These registers are effectively moved to the front of the
697 /// allocation order.
699 /// The Order argument is the allocation order for VirtReg's register class
700 /// as returned from RegisterClassInfo::getOrder(). The hint registers must
701 /// come from Order, and they must not be reserved.
703 /// The default implementation of this function can resolve
704 /// target-independent hints provided to MRI::setRegAllocationHint with
705 /// HintType == 0. Targets that override this function should defer to the
706 /// default implementation if they have no reason to change the allocation
707 /// order for VirtReg. There may be target-independent hints.
708 virtual void getRegAllocationHints(unsigned VirtReg,
709 ArrayRef<MCPhysReg> Order,
710 SmallVectorImpl<MCPhysReg> &Hints,
711 const MachineFunction &MF,
712 const VirtRegMap *VRM = nullptr) const;
714 /// updateRegAllocHint - A callback to allow target a chance to update
715 /// register allocation hints when a register is "changed" (e.g. coalesced)
716 /// to another register. e.g. On ARM, some virtual registers should target
717 /// register pairs, if one of pair is coalesced to another register, the
718 /// allocation hint of the other half of the pair should be changed to point
719 /// to the new register.
720 virtual void updateRegAllocHint(unsigned Reg, unsigned NewReg,
721 MachineFunction &MF) const {
725 /// Allow the target to reverse allocation order of local live ranges. This
726 /// will generally allocate shorter local live ranges first. For targets with
727 /// many registers, this could reduce regalloc compile time by a large
728 /// factor. It is disabled by default for three reasons:
729 /// (1) Top-down allocation is simpler and easier to debug for targets that
730 /// don't benefit from reversing the order.
731 /// (2) Bottom-up allocation could result in poor evicition decisions on some
732 /// targets affecting the performance of compiled code.
733 /// (3) Bottom-up allocation is no longer guaranteed to optimally color.
734 virtual bool reverseLocalAssignment() const { return false; }
736 /// Allow the target to override the cost of using a callee-saved register for
737 /// the first time. Default value of 0 means we will use a callee-saved
738 /// register if it is available.
739 virtual unsigned getCSRFirstUseCost() const { return 0; }
741 /// requiresRegisterScavenging - returns true if the target requires (and can
742 /// make use of) the register scavenger.
743 virtual bool requiresRegisterScavenging(const MachineFunction &MF) const {
747 /// useFPForScavengingIndex - returns true if the target wants to use
748 /// frame pointer based accesses to spill to the scavenger emergency spill
750 virtual bool useFPForScavengingIndex(const MachineFunction &MF) const {
754 /// requiresFrameIndexScavenging - returns true if the target requires post
755 /// PEI scavenging of registers for materializing frame index constants.
756 virtual bool requiresFrameIndexScavenging(const MachineFunction &MF) const {
760 /// requiresVirtualBaseRegisters - Returns true if the target wants the
761 /// LocalStackAllocation pass to be run and virtual base registers
762 /// used for more efficient stack access.
763 virtual bool requiresVirtualBaseRegisters(const MachineFunction &MF) const {
767 /// hasReservedSpillSlot - Return true if target has reserved a spill slot in
768 /// the stack frame of the given function for the specified register. e.g. On
769 /// x86, if the frame register is required, the first fixed stack object is
770 /// reserved as its spill slot. This tells PEI not to create a new stack frame
771 /// object for the given register. It should be called only after
772 /// processFunctionBeforeCalleeSavedScan().
773 virtual bool hasReservedSpillSlot(const MachineFunction &MF, unsigned Reg,
774 int &FrameIdx) const {
778 /// trackLivenessAfterRegAlloc - returns true if the live-ins should be tracked
779 /// after register allocation.
780 virtual bool trackLivenessAfterRegAlloc(const MachineFunction &MF) const {
784 /// needsStackRealignment - true if storage within the function requires the
785 /// stack pointer to be aligned more than the normal calling convention calls
787 virtual bool needsStackRealignment(const MachineFunction &MF) const {
791 /// getFrameIndexInstrOffset - Get the offset from the referenced frame
792 /// index in the instruction, if there is one.
793 virtual int64_t getFrameIndexInstrOffset(const MachineInstr *MI,
798 /// needsFrameBaseReg - Returns true if the instruction's frame index
799 /// reference would be better served by a base register other than FP
800 /// or SP. Used by LocalStackFrameAllocation to determine which frame index
801 /// references it should create new base registers for.
802 virtual bool needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const {
806 /// materializeFrameBaseRegister - Insert defining instruction(s) for
807 /// BaseReg to be a pointer to FrameIdx before insertion point I.
808 virtual void materializeFrameBaseRegister(MachineBasicBlock *MBB,
809 unsigned BaseReg, int FrameIdx,
810 int64_t Offset) const {
811 llvm_unreachable("materializeFrameBaseRegister does not exist on this "
815 /// resolveFrameIndex - Resolve a frame index operand of an instruction
816 /// to reference the indicated base register plus offset instead.
817 virtual void resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
818 int64_t Offset) const {
819 llvm_unreachable("resolveFrameIndex does not exist on this target");
822 /// isFrameOffsetLegal - Determine whether a given base register plus offset
823 /// immediate is encodable to resolve a frame index.
824 virtual bool isFrameOffsetLegal(const MachineInstr *MI, unsigned BaseReg,
825 int64_t Offset) const {
826 llvm_unreachable("isFrameOffsetLegal does not exist on this target");
830 /// saveScavengerRegister - Spill the register so it can be used by the
831 /// register scavenger. Return true if the register was spilled, false
832 /// otherwise. If this function does not spill the register, the scavenger
833 /// will instead spill it to the emergency spill slot.
835 virtual bool saveScavengerRegister(MachineBasicBlock &MBB,
836 MachineBasicBlock::iterator I,
837 MachineBasicBlock::iterator &UseMI,
838 const TargetRegisterClass *RC,
839 unsigned Reg) const {
843 /// eliminateFrameIndex - This method must be overriden to eliminate abstract
844 /// frame indices from instructions which may use them. The instruction
845 /// referenced by the iterator contains an MO_FrameIndex operand which must be
846 /// eliminated by this method. This method may modify or replace the
847 /// specified instruction, as long as it keeps the iterator pointing at the
848 /// finished product. SPAdj is the SP adjustment due to call frame setup
849 /// instruction. FIOperandNum is the FI operand number.
850 virtual void eliminateFrameIndex(MachineBasicBlock::iterator MI,
851 int SPAdj, unsigned FIOperandNum,
852 RegScavenger *RS = nullptr) const = 0;
854 //===--------------------------------------------------------------------===//
857 /// \brief SrcRC and DstRC will be morphed into NewRC if this returns true.
858 virtual bool shouldCoalesce(MachineInstr *MI,
859 const TargetRegisterClass *SrcRC,
861 const TargetRegisterClass *DstRC,
863 const TargetRegisterClass *NewRC) const
866 //===--------------------------------------------------------------------===//
867 /// Debug information queries.
869 /// getFrameRegister - This method should return the register used as a base
870 /// for values allocated in the current stack frame.
871 virtual unsigned getFrameRegister(const MachineFunction &MF) const = 0;
875 //===----------------------------------------------------------------------===//
876 // SuperRegClassIterator
877 //===----------------------------------------------------------------------===//
879 // Iterate over the possible super-registers for a given register class. The
880 // iterator will visit a list of pairs (Idx, Mask) corresponding to the
881 // possible classes of super-registers.
883 // Each bit mask will have at least one set bit, and each set bit in Mask
884 // corresponds to a SuperRC such that:
886 // For all Reg in SuperRC: Reg:Idx is in RC.
888 // The iterator can include (O, RC->getSubClassMask()) as the first entry which
889 // also satisfies the above requirement, assuming Reg:0 == Reg.
891 class SuperRegClassIterator {
892 const unsigned RCMaskWords;
895 const uint32_t *Mask;
898 /// Create a SuperRegClassIterator that visits all the super-register classes
899 /// of RC. When IncludeSelf is set, also include the (0, sub-classes) entry.
900 SuperRegClassIterator(const TargetRegisterClass *RC,
901 const TargetRegisterInfo *TRI,
902 bool IncludeSelf = false)
903 : RCMaskWords((TRI->getNumRegClasses() + 31) / 32),
905 Idx(RC->getSuperRegIndices()),
906 Mask(RC->getSubClassMask()) {
911 /// Returns true if this iterator is still pointing at a valid entry.
912 bool isValid() const { return Idx; }
914 /// Returns the current sub-register index.
915 unsigned getSubReg() const { return SubReg; }
917 /// Returns the bit mask if register classes that getSubReg() projects into
919 const uint32_t *getMask() const { return Mask; }
921 /// Advance iterator to the next entry.
923 assert(isValid() && "Cannot move iterator past end.");
931 // This is useful when building IndexedMaps keyed on virtual registers
932 struct VirtReg2IndexFunctor : public std::unary_function<unsigned, unsigned> {
933 unsigned operator()(unsigned Reg) const {
934 return TargetRegisterInfo::virtReg2Index(Reg);
938 /// PrintReg - Helper class for printing registers on a raw_ostream.
939 /// Prints virtual and physical registers with or without a TRI instance.
942 /// %noreg - NoRegister
943 /// %vreg5 - a virtual register.
944 /// %vreg5:sub_8bit - a virtual register with sub-register index (with TRI).
945 /// %EAX - a physical register
946 /// %physreg17 - a physical register when no TRI instance given.
948 /// Usage: OS << PrintReg(Reg, TRI) << '\n';
951 const TargetRegisterInfo *TRI;
955 explicit PrintReg(unsigned reg, const TargetRegisterInfo *tri = nullptr,
957 : TRI(tri), Reg(reg), SubIdx(subidx) {}
958 void print(raw_ostream&) const;
961 static inline raw_ostream &operator<<(raw_ostream &OS, const PrintReg &PR) {
966 /// PrintRegUnit - Helper class for printing register units on a raw_ostream.
968 /// Register units are named after their root registers:
970 /// AL - Single root.
971 /// FP0~ST7 - Dual roots.
973 /// Usage: OS << PrintRegUnit(Unit, TRI) << '\n';
977 const TargetRegisterInfo *TRI;
980 PrintRegUnit(unsigned unit, const TargetRegisterInfo *tri)
981 : TRI(tri), Unit(unit) {}
982 void print(raw_ostream&) const;
985 static inline raw_ostream &operator<<(raw_ostream &OS, const PrintRegUnit &PR) {
990 /// PrintVRegOrUnit - It is often convenient to track virtual registers and
991 /// physical register units in the same list.
992 class PrintVRegOrUnit : protected PrintRegUnit {
994 PrintVRegOrUnit(unsigned VRegOrUnit, const TargetRegisterInfo *tri)
995 : PrintRegUnit(VRegOrUnit, tri) {}
996 void print(raw_ostream&) const;
999 static inline raw_ostream &operator<<(raw_ostream &OS,
1000 const PrintVRegOrUnit &PR) {
1005 } // End llvm namespace