1 //==- CodeGen/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_CODEGEN_TARGETREGISTERINFO_H
17 #define LLVM_CODEGEN_TARGETREGISTERINFO_H
19 #include "llvm/ADT/ArrayRef.h"
20 #include "llvm/ADT/SmallVector.h"
21 #include "llvm/ADT/StringRef.h"
22 #include "llvm/ADT/iterator_range.h"
23 #include "llvm/CodeGen/MachineBasicBlock.h"
24 #include "llvm/IR/CallingConv.h"
25 #include "llvm/MC/LaneBitmask.h"
26 #include "llvm/MC/MCRegisterInfo.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/MachineValueType.h"
29 #include "llvm/Support/MathExtras.h"
30 #include "llvm/Support/Printable.h"
39 class MachineFunction;
45 class TargetRegisterClass {
47 using iterator = const MCPhysReg *;
48 using const_iterator = const MCPhysReg *;
49 using sc_iterator = const TargetRegisterClass* const *;
51 // Instance variables filled by tablegen, do not use!
52 const MCRegisterClass *MC;
53 const uint32_t *SubClassMask;
54 const uint16_t *SuperRegIndices;
55 const LaneBitmask LaneMask;
56 /// Classes with a higher priority value are assigned first by register
57 /// allocators using a greedy heuristic. The value is in the range [0,63].
58 const uint8_t AllocationPriority;
59 /// Whether the class supports two (or more) disjunct subregister indices.
60 const bool HasDisjunctSubRegs;
61 /// Whether a combination of subregisters can cover every register in the
62 /// class. See also the CoveredBySubRegs description in Target.td.
63 const bool CoveredBySubRegs;
64 const sc_iterator SuperClasses;
65 ArrayRef<MCPhysReg> (*OrderFunc)(const MachineFunction&);
67 /// Return the register class ID number.
68 unsigned getID() const { return MC->getID(); }
70 /// begin/end - Return all of the registers in this class.
72 iterator begin() const { return MC->begin(); }
73 iterator end() const { return MC->end(); }
75 /// Return the number of registers in this class.
76 unsigned getNumRegs() const { return MC->getNumRegs(); }
78 iterator_range<SmallVectorImpl<MCPhysReg>::const_iterator>
79 getRegisters() const {
80 return make_range(MC->begin(), MC->end());
83 /// Return the specified register in the class.
84 unsigned getRegister(unsigned i) const {
85 return MC->getRegister(i);
88 /// Return true if the specified register is included in this register class.
89 /// This does not include virtual registers.
90 bool contains(unsigned Reg) const {
91 return MC->contains(Reg);
94 /// Return true if both registers are in this class.
95 bool contains(unsigned Reg1, unsigned Reg2) const {
96 return MC->contains(Reg1, Reg2);
99 /// Return the cost of copying a value between two registers in this class.
100 /// A negative number means the register class is very expensive
101 /// to copy e.g. status flag register classes.
102 int getCopyCost() const { return MC->getCopyCost(); }
104 /// Return true if this register class may be used to create virtual
106 bool isAllocatable() const { return MC->isAllocatable(); }
108 /// Return true if the specified TargetRegisterClass
109 /// is a proper sub-class of this TargetRegisterClass.
110 bool hasSubClass(const TargetRegisterClass *RC) const {
111 return RC != this && hasSubClassEq(RC);
114 /// Returns true if RC is a sub-class of or equal to this class.
115 bool hasSubClassEq(const TargetRegisterClass *RC) const {
116 unsigned ID = RC->getID();
117 return (SubClassMask[ID / 32] >> (ID % 32)) & 1;
120 /// Return true if the specified TargetRegisterClass is a
121 /// proper super-class of this TargetRegisterClass.
122 bool hasSuperClass(const TargetRegisterClass *RC) const {
123 return RC->hasSubClass(this);
126 /// Returns true if RC is a super-class of or equal to this class.
127 bool hasSuperClassEq(const TargetRegisterClass *RC) const {
128 return RC->hasSubClassEq(this);
131 /// Returns a bit vector of subclasses, including this one.
132 /// The vector is indexed by class IDs.
134 /// To use it, consider the returned array as a chunk of memory that
135 /// contains an array of bits of size NumRegClasses. Each 32-bit chunk
136 /// contains a bitset of the ID of the subclasses in big-endian style.
138 /// I.e., the representation of the memory from left to right at the
139 /// bit level looks like:
140 /// [31 30 ... 1 0] [ 63 62 ... 33 32] ...
141 /// [ XXX NumRegClasses NumRegClasses - 1 ... ]
142 /// Where the number represents the class ID and XXX bits that
143 /// should be ignored.
145 /// See the implementation of hasSubClassEq for an example of how it
147 const uint32_t *getSubClassMask() const {
151 /// Returns a 0-terminated list of sub-register indices that project some
152 /// super-register class into this register class. The list has an entry for
153 /// each Idx such that:
155 /// There exists SuperRC where:
156 /// For all Reg in SuperRC:
157 /// this->contains(Reg:Idx)
158 const uint16_t *getSuperRegIndices() const {
159 return SuperRegIndices;
162 /// Returns a NULL-terminated list of super-classes. The
163 /// classes are ordered by ID which is also a topological ordering from large
164 /// to small classes. The list does NOT include the current class.
165 sc_iterator getSuperClasses() const {
169 /// Return true if this TargetRegisterClass is a subset
170 /// class of at least one other TargetRegisterClass.
171 bool isASubClass() const {
172 return SuperClasses[0] != nullptr;
175 /// Returns the preferred order for allocating registers from this register
176 /// class in MF. The raw order comes directly from the .td file and may
177 /// include reserved registers that are not allocatable.
178 /// Register allocators should also make sure to allocate
179 /// callee-saved registers only after all the volatiles are used. The
180 /// RegisterClassInfo class provides filtered allocation orders with
181 /// callee-saved registers moved to the end.
183 /// The MachineFunction argument can be used to tune the allocatable
184 /// registers based on the characteristics of the function, subtarget, or
187 /// By default, this method returns all registers in the class.
188 ArrayRef<MCPhysReg> getRawAllocationOrder(const MachineFunction &MF) const {
189 return OrderFunc ? OrderFunc(MF) : makeArrayRef(begin(), getNumRegs());
192 /// Returns the combination of all lane masks of register in this class.
193 /// The lane masks of the registers are the combination of all lane masks
194 /// of their subregisters. Returns 1 if there are no subregisters.
195 LaneBitmask getLaneMask() const {
200 /// Extra information, not in MCRegisterDesc, about registers.
201 /// These are used by codegen, not by MC.
202 struct TargetRegisterInfoDesc {
203 unsigned CostPerUse; // Extra cost of instructions using register.
204 bool inAllocatableClass; // Register belongs to an allocatable regclass.
207 /// Each TargetRegisterClass has a per register weight, and weight
208 /// limit which must be less than the limits of its pressure sets.
209 struct RegClassWeight {
211 unsigned WeightLimit;
214 /// TargetRegisterInfo base class - We assume that the target defines a static
215 /// array of TargetRegisterDesc objects that represent all of the machine
216 /// registers that the target has. As such, we simply have to track a pointer
217 /// to this array so that we can turn register number into a register
220 class TargetRegisterInfo : public MCRegisterInfo {
222 using regclass_iterator = const TargetRegisterClass * const *;
223 using vt_iterator = const MVT::SimpleValueType *;
224 struct RegClassInfo {
225 unsigned RegSize, SpillSize, SpillAlignment;
229 const TargetRegisterInfoDesc *InfoDesc; // Extra desc array for codegen
230 const char *const *SubRegIndexNames; // Names of subreg indexes.
231 // Pointer to array of lane masks, one per sub-reg index.
232 const LaneBitmask *SubRegIndexLaneMasks;
234 regclass_iterator RegClassBegin, RegClassEnd; // List of regclasses
235 LaneBitmask CoveringLanes;
236 const RegClassInfo *const RCInfos;
240 TargetRegisterInfo(const TargetRegisterInfoDesc *ID,
241 regclass_iterator RCB,
242 regclass_iterator RCE,
243 const char *const *SRINames,
244 const LaneBitmask *SRILaneMasks,
245 LaneBitmask CoveringLanes,
246 const RegClassInfo *const RCIs,
248 virtual ~TargetRegisterInfo();
251 // Register numbers can represent physical registers, virtual registers, and
252 // sometimes stack slots. The unsigned values are divided into these ranges:
254 // 0 Not a register, can be used as a sentinel.
255 // [1;2^30) Physical registers assigned by TableGen.
256 // [2^30;2^31) Stack slots. (Rarely used.)
257 // [2^31;2^32) Virtual registers assigned by MachineRegisterInfo.
259 // Further sentinels can be allocated from the small negative integers.
260 // DenseMapInfo<unsigned> uses -1u and -2u.
262 /// isStackSlot - Sometimes it is useful the be able to store a non-negative
263 /// frame index in a variable that normally holds a register. isStackSlot()
264 /// returns true if Reg is in the range used for stack slots.
266 /// Note that isVirtualRegister() and isPhysicalRegister() cannot handle stack
267 /// slots, so if a variable may contains a stack slot, always check
268 /// isStackSlot() first.
270 static bool isStackSlot(unsigned Reg) {
271 return int(Reg) >= (1 << 30);
274 /// Compute the frame index from a register value 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 /// Convert a non-negative frame index to a stack slot register value.
281 static unsigned index2StackSlot(int FI) {
282 assert(FI >= 0 && "Cannot hold a negative frame index.");
283 return FI + (1u << 30);
286 /// Return true if the specified register number is in
287 /// the physical register namespace.
288 static bool isPhysicalRegister(unsigned Reg) {
289 assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
293 /// Return true if the specified register number is in
294 /// the virtual register namespace.
295 static bool isVirtualRegister(unsigned Reg) {
296 assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
300 /// Convert a virtual register number to a 0-based index.
301 /// The first virtual register in a function will get the index 0.
302 static unsigned virtReg2Index(unsigned Reg) {
303 assert(isVirtualRegister(Reg) && "Not a virtual register");
304 return Reg & ~(1u << 31);
307 /// Convert a 0-based index to a virtual register number.
308 /// This is the inverse operation of VirtReg2IndexFunctor below.
309 static unsigned index2VirtReg(unsigned Index) {
310 return Index | (1u << 31);
313 /// Return the size in bits of a register from class RC.
314 unsigned getRegSizeInBits(const TargetRegisterClass &RC) const {
315 return getRegClassInfo(RC).RegSize;
318 /// Return the size in bytes of the stack slot allocated to hold a spilled
319 /// copy of a register from class RC.
320 unsigned getSpillSize(const TargetRegisterClass &RC) const {
321 return getRegClassInfo(RC).SpillSize / 8;
324 /// Return the minimum required alignment in bytes for a spill slot for
325 /// a register of this class.
326 unsigned getSpillAlignment(const TargetRegisterClass &RC) const {
327 return getRegClassInfo(RC).SpillAlignment / 8;
330 /// Return true if the given TargetRegisterClass has the ValueType T.
331 bool isTypeLegalForClass(const TargetRegisterClass &RC, MVT T) const {
332 for (auto I = legalclasstypes_begin(RC); *I != MVT::Other; ++I)
338 /// Loop over all of the value types that can be represented by values
339 /// in the given register class.
340 vt_iterator legalclasstypes_begin(const TargetRegisterClass &RC) const {
341 return getRegClassInfo(RC).VTList;
344 vt_iterator legalclasstypes_end(const TargetRegisterClass &RC) const {
345 vt_iterator I = legalclasstypes_begin(RC);
346 while (*I != MVT::Other)
351 /// Returns the Register Class of a physical register of the given type,
352 /// picking the most sub register class of the right type that contains this
354 const TargetRegisterClass *
355 getMinimalPhysRegClass(unsigned Reg, MVT VT = MVT::Other) const;
357 /// Return the maximal subclass of the given register class that is
358 /// allocatable or NULL.
359 const TargetRegisterClass *
360 getAllocatableClass(const TargetRegisterClass *RC) const;
362 /// Returns a bitset indexed by register number indicating if a register is
363 /// allocatable or not. If a register class is specified, returns the subset
365 BitVector getAllocatableSet(const MachineFunction &MF,
366 const TargetRegisterClass *RC = nullptr) const;
368 /// Return the additional cost of using this register instead
369 /// of other registers in its class.
370 unsigned getCostPerUse(unsigned RegNo) const {
371 return InfoDesc[RegNo].CostPerUse;
374 /// Return true if the register is in the allocation of any register class.
375 bool isInAllocatableClass(unsigned RegNo) const {
376 return InfoDesc[RegNo].inAllocatableClass;
379 /// Return the human-readable symbolic target-specific
380 /// name for the specified SubRegIndex.
381 const char *getSubRegIndexName(unsigned SubIdx) const {
382 assert(SubIdx && SubIdx < getNumSubRegIndices() &&
383 "This is not a subregister index");
384 return SubRegIndexNames[SubIdx-1];
387 /// Return a bitmask representing the parts of a register that are covered by
388 /// SubIdx \see LaneBitmask.
390 /// SubIdx == 0 is allowed, it has the lane mask ~0u.
391 LaneBitmask getSubRegIndexLaneMask(unsigned SubIdx) const {
392 assert(SubIdx < getNumSubRegIndices() && "This is not a subregister index");
393 return SubRegIndexLaneMasks[SubIdx];
396 /// The lane masks returned by getSubRegIndexLaneMask() above can only be
397 /// used to determine if sub-registers overlap - they can't be used to
398 /// determine if a set of sub-registers completely cover another
401 /// The X86 general purpose registers have two lanes corresponding to the
402 /// sub_8bit and sub_8bit_hi sub-registers. Both sub_32bit and sub_16bit have
403 /// lane masks '3', but the sub_16bit sub-register doesn't fully cover the
404 /// sub_32bit sub-register.
406 /// On the other hand, the ARM NEON lanes fully cover their registers: The
407 /// dsub_0 sub-register is completely covered by the ssub_0 and ssub_1 lanes.
408 /// This is related to the CoveredBySubRegs property on register definitions.
410 /// This function returns a bit mask of lanes that completely cover their
411 /// sub-registers. More precisely, given:
413 /// Covering = getCoveringLanes();
414 /// MaskA = getSubRegIndexLaneMask(SubA);
415 /// MaskB = getSubRegIndexLaneMask(SubB);
417 /// If (MaskA & ~(MaskB & Covering)) == 0, then SubA is completely covered by
419 LaneBitmask getCoveringLanes() const { return CoveringLanes; }
421 /// Returns true if the two registers are equal or alias each other.
422 /// The registers may be virtual registers.
423 bool regsOverlap(unsigned regA, unsigned regB) const {
424 if (regA == regB) return true;
425 if (isVirtualRegister(regA) || isVirtualRegister(regB))
428 // Regunits are numerically ordered. Find a common unit.
429 MCRegUnitIterator RUA(regA, this);
430 MCRegUnitIterator RUB(regB, this);
432 if (*RUA == *RUB) return true;
433 if (*RUA < *RUB) ++RUA;
435 } while (RUA.isValid() && RUB.isValid());
439 /// Returns true if Reg contains RegUnit.
440 bool hasRegUnit(unsigned Reg, unsigned RegUnit) const {
441 for (MCRegUnitIterator Units(Reg, this); Units.isValid(); ++Units)
442 if (*Units == RegUnit)
447 /// Returns the original SrcReg unless it is the target of a copy-like
448 /// operation, in which case we chain backwards through all such operations
449 /// to the ultimate source register. If a physical register is encountered,
450 /// we stop the search.
451 virtual unsigned lookThruCopyLike(unsigned SrcReg,
452 const MachineRegisterInfo *MRI) const;
454 /// Return a null-terminated list of all of the callee-saved registers on
455 /// this target. The register should be in the order of desired callee-save
456 /// stack frame offset. The first register is closest to the incoming stack
457 /// pointer if stack grows down, and vice versa.
458 /// Notice: This function does not take into account disabled CSRs.
459 /// In most cases you will want to use instead the function
460 /// getCalleeSavedRegs that is implemented in MachineRegisterInfo.
461 virtual const MCPhysReg*
462 getCalleeSavedRegs(const MachineFunction *MF) const = 0;
464 /// Return a mask of call-preserved registers for the given calling convention
465 /// on the current function. The mask should include all call-preserved
466 /// aliases. This is used by the register allocator to determine which
467 /// registers can be live across a call.
469 /// The mask is an array containing (TRI::getNumRegs()+31)/32 entries.
470 /// A set bit indicates that all bits of the corresponding register are
471 /// preserved across the function call. The bit mask is expected to be
472 /// sub-register complete, i.e. if A is preserved, so are all its
475 /// Bits are numbered from the LSB, so the bit for physical register Reg can
476 /// be found as (Mask[Reg / 32] >> Reg % 32) & 1.
478 /// A NULL pointer means that no register mask will be used, and call
479 /// instructions should use implicit-def operands to indicate call clobbered
482 virtual const uint32_t *getCallPreservedMask(const MachineFunction &MF,
483 CallingConv::ID) const {
484 // The default mask clobbers everything. All targets should override.
488 /// Return a register mask that clobbers everything.
489 virtual const uint32_t *getNoPreservedMask() const {
490 llvm_unreachable("target does not provide no preserved mask");
493 /// Return true if all bits that are set in mask \p mask0 are also set in
495 bool regmaskSubsetEqual(const uint32_t *mask0, const uint32_t *mask1) const;
497 /// Return all the call-preserved register masks defined for this target.
498 virtual ArrayRef<const uint32_t *> getRegMasks() const = 0;
499 virtual ArrayRef<const char *> getRegMaskNames() const = 0;
501 /// Returns a bitset indexed by physical register number indicating if a
502 /// register is a special register that has particular uses and should be
503 /// considered unavailable at all times, e.g. stack pointer, return address.
504 /// A reserved register:
505 /// - is not allocatable
506 /// - is considered always live
507 /// - is ignored by liveness tracking
508 /// It is often necessary to reserve the super registers of a reserved
509 /// register as well, to avoid them getting allocated indirectly. You may use
510 /// markSuperRegs() and checkAllSuperRegsMarked() in this case.
511 virtual BitVector getReservedRegs(const MachineFunction &MF) const = 0;
513 /// Returns true if PhysReg is unallocatable and constant throughout the
514 /// function. Used by MachineRegisterInfo::isConstantPhysReg().
515 virtual bool isConstantPhysReg(unsigned PhysReg) const { return false; }
517 /// Physical registers that may be modified within a function but are
518 /// guaranteed to be restored before any uses. This is useful for targets that
519 /// have call sequences where a GOT register may be updated by the caller
520 /// prior to a call and is guaranteed to be restored (also by the caller)
522 virtual bool isCallerPreservedPhysReg(unsigned PhysReg,
523 const MachineFunction &MF) const {
527 /// Prior to adding the live-out mask to a stackmap or patchpoint
528 /// instruction, provide the target the opportunity to adjust it (mainly to
529 /// remove pseudo-registers that should be ignored).
530 virtual void adjustStackMapLiveOutMask(uint32_t *Mask) const {}
532 /// Return a super-register of the specified register
533 /// Reg so its sub-register of index SubIdx is Reg.
534 unsigned getMatchingSuperReg(unsigned Reg, unsigned SubIdx,
535 const TargetRegisterClass *RC) const {
536 return MCRegisterInfo::getMatchingSuperReg(Reg, SubIdx, RC->MC);
539 /// Return a subclass of the specified register
540 /// class A so that each register in it has a sub-register of the
541 /// specified sub-register index which is in the specified register class B.
543 /// TableGen will synthesize missing A sub-classes.
544 virtual const TargetRegisterClass *
545 getMatchingSuperRegClass(const TargetRegisterClass *A,
546 const TargetRegisterClass *B, unsigned Idx) const;
548 // For a copy-like instruction that defines a register of class DefRC with
549 // subreg index DefSubReg, reading from another source with class SrcRC and
550 // subregister SrcSubReg return true if this is a preferable copy
551 // instruction or an earlier use should be used.
552 virtual bool shouldRewriteCopySrc(const TargetRegisterClass *DefRC,
554 const TargetRegisterClass *SrcRC,
555 unsigned SrcSubReg) const;
557 /// Returns the largest legal sub-class of RC that
558 /// supports the sub-register index Idx.
559 /// If no such sub-class exists, return NULL.
560 /// If all registers in RC already have an Idx sub-register, return RC.
562 /// TableGen generates a version of this function that is good enough in most
563 /// cases. Targets can override if they have constraints that TableGen
564 /// doesn't understand. For example, the x86 sub_8bit sub-register index is
565 /// supported by the full GR32 register class in 64-bit mode, but only by the
566 /// GR32_ABCD regiister class in 32-bit mode.
568 /// TableGen will synthesize missing RC sub-classes.
569 virtual const TargetRegisterClass *
570 getSubClassWithSubReg(const TargetRegisterClass *RC, unsigned Idx) const {
571 assert(Idx == 0 && "Target has no sub-registers");
575 /// Return the subregister index you get from composing
576 /// two subregister indices.
578 /// The special null sub-register index composes as the identity.
580 /// If R:a:b is the same register as R:c, then composeSubRegIndices(a, b)
581 /// returns c. Note that composeSubRegIndices does not tell you about illegal
582 /// compositions. If R does not have a subreg a, or R:a does not have a subreg
583 /// b, composeSubRegIndices doesn't tell you.
585 /// The ARM register Q0 has two D subregs dsub_0:D0 and dsub_1:D1. It also has
586 /// ssub_0:S0 - ssub_3:S3 subregs.
587 /// If you compose subreg indices dsub_1, ssub_0 you get ssub_2.
588 unsigned composeSubRegIndices(unsigned a, unsigned b) const {
591 return composeSubRegIndicesImpl(a, b);
594 /// Transforms a LaneMask computed for one subregister to the lanemask that
595 /// would have been computed when composing the subsubregisters with IdxA
596 /// first. @sa composeSubRegIndices()
597 LaneBitmask composeSubRegIndexLaneMask(unsigned IdxA,
598 LaneBitmask Mask) const {
601 return composeSubRegIndexLaneMaskImpl(IdxA, Mask);
604 /// Transform a lanemask given for a virtual register to the corresponding
605 /// lanemask before using subregister with index \p IdxA.
606 /// This is the reverse of composeSubRegIndexLaneMask(), assuming Mask is a
607 /// valie lane mask (no invalid bits set) the following holds:
608 /// X0 = composeSubRegIndexLaneMask(Idx, Mask)
609 /// X1 = reverseComposeSubRegIndexLaneMask(Idx, X0)
611 LaneBitmask reverseComposeSubRegIndexLaneMask(unsigned IdxA,
612 LaneBitmask LaneMask) const {
615 return reverseComposeSubRegIndexLaneMaskImpl(IdxA, LaneMask);
618 /// Debugging helper: dump register in human readable form to dbgs() stream.
619 static void dumpReg(unsigned Reg, unsigned SubRegIndex = 0,
620 const TargetRegisterInfo* TRI = nullptr);
623 /// Overridden by TableGen in targets that have sub-registers.
624 virtual unsigned composeSubRegIndicesImpl(unsigned, unsigned) const {
625 llvm_unreachable("Target has no sub-registers");
628 /// Overridden by TableGen in targets that have sub-registers.
630 composeSubRegIndexLaneMaskImpl(unsigned, LaneBitmask) const {
631 llvm_unreachable("Target has no sub-registers");
634 virtual LaneBitmask reverseComposeSubRegIndexLaneMaskImpl(unsigned,
636 llvm_unreachable("Target has no sub-registers");
640 /// Find a common super-register class if it exists.
642 /// Find a register class, SuperRC and two sub-register indices, PreA and
645 /// 1. PreA + SubA == PreB + SubB (using composeSubRegIndices()), and
647 /// 2. For all Reg in SuperRC: Reg:PreA in RCA and Reg:PreB in RCB, and
649 /// 3. SuperRC->getSize() >= max(RCA->getSize(), RCB->getSize()).
651 /// SuperRC will be chosen such that no super-class of SuperRC satisfies the
652 /// requirements, and there is no register class with a smaller spill size
653 /// that satisfies the requirements.
655 /// SubA and SubB must not be 0. Use getMatchingSuperRegClass() instead.
657 /// Either of the PreA and PreB sub-register indices may be returned as 0. In
658 /// that case, the returned register class will be a sub-class of the
659 /// corresponding argument register class.
661 /// The function returns NULL if no register class can be found.
662 const TargetRegisterClass*
663 getCommonSuperRegClass(const TargetRegisterClass *RCA, unsigned SubA,
664 const TargetRegisterClass *RCB, unsigned SubB,
665 unsigned &PreA, unsigned &PreB) const;
667 //===--------------------------------------------------------------------===//
668 // Register Class Information
671 const RegClassInfo &getRegClassInfo(const TargetRegisterClass &RC) const {
672 return RCInfos[getNumRegClasses() * HwMode + RC.getID()];
676 /// Register class iterators
677 regclass_iterator regclass_begin() const { return RegClassBegin; }
678 regclass_iterator regclass_end() const { return RegClassEnd; }
679 iterator_range<regclass_iterator> regclasses() const {
680 return make_range(regclass_begin(), regclass_end());
683 unsigned getNumRegClasses() const {
684 return (unsigned)(regclass_end()-regclass_begin());
687 /// Returns the register class associated with the enumeration value.
688 /// See class MCOperandInfo.
689 const TargetRegisterClass *getRegClass(unsigned i) const {
690 assert(i < getNumRegClasses() && "Register Class ID out of range");
691 return RegClassBegin[i];
694 /// Returns the name of the register class.
695 const char *getRegClassName(const TargetRegisterClass *Class) const {
696 return MCRegisterInfo::getRegClassName(Class->MC);
699 /// Find the largest common subclass of A and B.
700 /// Return NULL if there is no common subclass.
701 /// The common subclass should contain
702 /// simple value type SVT if it is not the Any type.
703 const TargetRegisterClass *
704 getCommonSubClass(const TargetRegisterClass *A,
705 const TargetRegisterClass *B,
706 const MVT::SimpleValueType SVT =
707 MVT::SimpleValueType::Any) const;
709 /// Returns a TargetRegisterClass used for pointer values.
710 /// If a target supports multiple different pointer register classes,
711 /// kind specifies which one is indicated.
712 virtual const TargetRegisterClass *
713 getPointerRegClass(const MachineFunction &MF, unsigned Kind=0) const {
714 llvm_unreachable("Target didn't implement getPointerRegClass!");
717 /// Returns a legal register class to copy a register in the specified class
718 /// to or from. If it is possible to copy the register directly without using
719 /// a cross register class copy, return the specified RC. Returns NULL if it
720 /// is not possible to copy between two registers of the specified class.
721 virtual const TargetRegisterClass *
722 getCrossCopyRegClass(const TargetRegisterClass *RC) const {
726 /// Returns the largest super class of RC that is legal to use in the current
727 /// sub-target and has the same spill size.
728 /// The returned register class can be used to create virtual registers which
729 /// means that all its registers can be copied and spilled.
730 virtual const TargetRegisterClass *
731 getLargestLegalSuperClass(const TargetRegisterClass *RC,
732 const MachineFunction &) const {
733 /// The default implementation is very conservative and doesn't allow the
734 /// register allocator to inflate register classes.
738 /// Return the register pressure "high water mark" for the specific register
739 /// class. The scheduler is in high register pressure mode (for the specific
740 /// register class) if it goes over the limit.
742 /// Note: this is the old register pressure model that relies on a manually
743 /// specified representative register class per value type.
744 virtual unsigned getRegPressureLimit(const TargetRegisterClass *RC,
745 MachineFunction &MF) const {
749 /// Return a heuristic for the machine scheduler to compare the profitability
750 /// of increasing one register pressure set versus another. The scheduler
751 /// will prefer increasing the register pressure of the set which returns
752 /// the largest value for this function.
753 virtual unsigned getRegPressureSetScore(const MachineFunction &MF,
754 unsigned PSetID) const {
758 /// Get the weight in units of pressure for this register class.
759 virtual const RegClassWeight &getRegClassWeight(
760 const TargetRegisterClass *RC) const = 0;
762 /// Returns size in bits of a phys/virtual/generic register.
763 unsigned getRegSizeInBits(unsigned Reg, const MachineRegisterInfo &MRI) const;
765 /// Get the weight in units of pressure for this register unit.
766 virtual unsigned getRegUnitWeight(unsigned RegUnit) const = 0;
768 /// Get the number of dimensions of register pressure.
769 virtual unsigned getNumRegPressureSets() const = 0;
771 /// Get the name of this register unit pressure set.
772 virtual const char *getRegPressureSetName(unsigned Idx) const = 0;
774 /// Get the register unit pressure limit for this dimension.
775 /// This limit must be adjusted dynamically for reserved registers.
776 virtual unsigned getRegPressureSetLimit(const MachineFunction &MF,
777 unsigned Idx) const = 0;
779 /// Get the dimensions of register pressure impacted by this register class.
780 /// Returns a -1 terminated array of pressure set IDs.
781 virtual const int *getRegClassPressureSets(
782 const TargetRegisterClass *RC) const = 0;
784 /// Get the dimensions of register pressure impacted by this register unit.
785 /// Returns a -1 terminated array of pressure set IDs.
786 virtual const int *getRegUnitPressureSets(unsigned RegUnit) const = 0;
788 /// Get a list of 'hint' registers that the register allocator should try
789 /// first when allocating a physical register for the virtual register
790 /// VirtReg. These registers are effectively moved to the front of the
791 /// allocation order. If true is returned, regalloc will try to only use
792 /// hints to the greatest extent possible even if it means spilling.
794 /// The Order argument is the allocation order for VirtReg's register class
795 /// as returned from RegisterClassInfo::getOrder(). The hint registers must
796 /// come from Order, and they must not be reserved.
798 /// The default implementation of this function will only add target
799 /// independent register allocation hints. Targets that override this
800 /// function should typically call this default implementation as well and
801 /// expect to see generic copy hints added.
802 virtual bool getRegAllocationHints(unsigned VirtReg,
803 ArrayRef<MCPhysReg> Order,
804 SmallVectorImpl<MCPhysReg> &Hints,
805 const MachineFunction &MF,
806 const VirtRegMap *VRM = nullptr,
807 const LiveRegMatrix *Matrix = nullptr)
810 /// A callback to allow target a chance to update register allocation hints
811 /// when a register is "changed" (e.g. coalesced) to another register.
812 /// e.g. On ARM, some virtual registers should target register pairs,
813 /// if one of pair is coalesced to another register, the allocation hint of
814 /// the other half of the pair should be changed to point to the new register.
815 virtual void updateRegAllocHint(unsigned Reg, unsigned NewReg,
816 MachineFunction &MF) const {
820 /// The creation of multiple copy hints have been implemented in
821 /// weightCalcHelper(), but since this affects so many tests for many
822 /// targets, this is temporarily disabled per default. THIS SHOULD BE
823 /// "GENERAL GOODNESS" and hopefully all targets will update their tests
824 /// and enable this soon. This hook should then be removed.
825 virtual bool enableMultipleCopyHints() const { return false; }
827 /// Allow the target to reverse allocation order of local live ranges. This
828 /// will generally allocate shorter local live ranges first. For targets with
829 /// many registers, this could reduce regalloc compile time by a large
830 /// factor. It is disabled by default for three reasons:
831 /// (1) Top-down allocation is simpler and easier to debug for targets that
832 /// don't benefit from reversing the order.
833 /// (2) Bottom-up allocation could result in poor evicition decisions on some
834 /// targets affecting the performance of compiled code.
835 /// (3) Bottom-up allocation is no longer guaranteed to optimally color.
836 virtual bool reverseLocalAssignment() const { return false; }
838 /// Allow the target to override the cost of using a callee-saved register for
839 /// the first time. Default value of 0 means we will use a callee-saved
840 /// register if it is available.
841 virtual unsigned getCSRFirstUseCost() const { return 0; }
843 /// Returns true if the target requires (and can make use of) the register
845 virtual bool requiresRegisterScavenging(const MachineFunction &MF) const {
849 /// Returns true if the target wants to use frame pointer based accesses to
850 /// spill to the scavenger emergency spill slot.
851 virtual bool useFPForScavengingIndex(const MachineFunction &MF) const {
855 /// Returns true if the target requires post PEI scavenging of registers for
856 /// materializing frame index constants.
857 virtual bool requiresFrameIndexScavenging(const MachineFunction &MF) const {
861 /// Returns true if the target requires using the RegScavenger directly for
862 /// frame elimination despite using requiresFrameIndexScavenging.
863 virtual bool requiresFrameIndexReplacementScavenging(
864 const MachineFunction &MF) const {
868 /// Returns true if the target wants the LocalStackAllocation pass to be run
869 /// and virtual base registers used for more efficient stack access.
870 virtual bool requiresVirtualBaseRegisters(const MachineFunction &MF) const {
874 /// Return true if target has reserved a spill slot in the stack frame of
875 /// the given function for the specified register. e.g. On x86, if the frame
876 /// register is required, the first fixed stack object is reserved as its
877 /// spill slot. This tells PEI not to create a new stack frame
878 /// object for the given register. It should be called only after
879 /// determineCalleeSaves().
880 virtual bool hasReservedSpillSlot(const MachineFunction &MF, unsigned Reg,
881 int &FrameIdx) const {
885 /// Returns true if the live-ins should be tracked after register allocation.
886 virtual bool trackLivenessAfterRegAlloc(const MachineFunction &MF) const {
890 /// True if the stack can be realigned for the target.
891 virtual bool canRealignStack(const MachineFunction &MF) const;
893 /// True if storage within the function requires the stack pointer to be
894 /// aligned more than the normal calling convention calls for.
895 /// This cannot be overriden by the target, but canRealignStack can be
897 bool needsStackRealignment(const MachineFunction &MF) const;
899 /// Get the offset from the referenced frame index in the instruction,
901 virtual int64_t getFrameIndexInstrOffset(const MachineInstr *MI,
906 /// Returns true if the instruction's frame index reference would be better
907 /// served by a base register other than FP or SP.
908 /// Used by LocalStackFrameAllocation to determine which frame index
909 /// references it should create new base registers for.
910 virtual bool needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const {
914 /// Insert defining instruction(s) for BaseReg to be a pointer to FrameIdx
915 /// before insertion point I.
916 virtual void materializeFrameBaseRegister(MachineBasicBlock *MBB,
917 unsigned BaseReg, int FrameIdx,
918 int64_t Offset) const {
919 llvm_unreachable("materializeFrameBaseRegister does not exist on this "
923 /// Resolve a frame index operand of an instruction
924 /// to reference the indicated base register plus offset instead.
925 virtual void resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
926 int64_t Offset) const {
927 llvm_unreachable("resolveFrameIndex does not exist on this target");
930 /// Determine whether a given base register plus offset immediate is
931 /// encodable to resolve a frame index.
932 virtual bool isFrameOffsetLegal(const MachineInstr *MI, unsigned BaseReg,
933 int64_t Offset) const {
934 llvm_unreachable("isFrameOffsetLegal does not exist on this target");
937 /// Spill the register so it can be used by the register scavenger.
938 /// Return true if the register was spilled, false otherwise.
939 /// If this function does not spill the register, the scavenger
940 /// will instead spill it to the emergency spill slot.
941 virtual bool saveScavengerRegister(MachineBasicBlock &MBB,
942 MachineBasicBlock::iterator I,
943 MachineBasicBlock::iterator &UseMI,
944 const TargetRegisterClass *RC,
945 unsigned Reg) const {
949 /// This method must be overriden to eliminate abstract frame indices from
950 /// instructions which may use them. The instruction referenced by the
951 /// iterator contains an MO_FrameIndex operand which must be eliminated by
952 /// this method. This method may modify or replace the specified instruction,
953 /// as long as it keeps the iterator pointing at the finished product.
954 /// SPAdj is the SP adjustment due to call frame setup instruction.
955 /// FIOperandNum is the FI operand number.
956 virtual void eliminateFrameIndex(MachineBasicBlock::iterator MI,
957 int SPAdj, unsigned FIOperandNum,
958 RegScavenger *RS = nullptr) const = 0;
960 /// Return the assembly name for \p Reg.
961 virtual StringRef getRegAsmName(unsigned Reg) const {
962 // FIXME: We are assuming that the assembly name is equal to the TableGen
963 // name converted to lower case
965 // The TableGen name is the name of the definition for this register in the
966 // target's tablegen files. For example, the TableGen name of
967 // def EAX : Register <...>; is "EAX"
968 return StringRef(getName(Reg));
971 //===--------------------------------------------------------------------===//
974 /// SrcRC and DstRC will be morphed into NewRC if this returns true.
975 virtual bool shouldCoalesce(MachineInstr *MI,
976 const TargetRegisterClass *SrcRC,
978 const TargetRegisterClass *DstRC,
980 const TargetRegisterClass *NewRC,
981 LiveIntervals &LIS) const
984 //===--------------------------------------------------------------------===//
985 /// Debug information queries.
987 /// getFrameRegister - This method should return the register used as a base
988 /// for values allocated in the current stack frame.
989 virtual unsigned getFrameRegister(const MachineFunction &MF) const = 0;
991 /// Mark a register and all its aliases as reserved in the given set.
992 void markSuperRegs(BitVector &RegisterSet, unsigned Reg) const;
994 /// Returns true if for every register in the set all super registers are part
995 /// of the set as well.
996 bool checkAllSuperRegsMarked(const BitVector &RegisterSet,
997 ArrayRef<MCPhysReg> Exceptions = ArrayRef<MCPhysReg>()) const;
999 virtual const TargetRegisterClass *
1000 getConstrainedRegClassForOperand(const MachineOperand &MO,
1001 const MachineRegisterInfo &MRI) const {
1006 //===----------------------------------------------------------------------===//
1007 // SuperRegClassIterator
1008 //===----------------------------------------------------------------------===//
1010 // Iterate over the possible super-registers for a given register class. The
1011 // iterator will visit a list of pairs (Idx, Mask) corresponding to the
1012 // possible classes of super-registers.
1014 // Each bit mask will have at least one set bit, and each set bit in Mask
1015 // corresponds to a SuperRC such that:
1017 // For all Reg in SuperRC: Reg:Idx is in RC.
1019 // The iterator can include (O, RC->getSubClassMask()) as the first entry which
1020 // also satisfies the above requirement, assuming Reg:0 == Reg.
1022 class SuperRegClassIterator {
1023 const unsigned RCMaskWords;
1024 unsigned SubReg = 0;
1025 const uint16_t *Idx;
1026 const uint32_t *Mask;
1029 /// Create a SuperRegClassIterator that visits all the super-register classes
1030 /// of RC. When IncludeSelf is set, also include the (0, sub-classes) entry.
1031 SuperRegClassIterator(const TargetRegisterClass *RC,
1032 const TargetRegisterInfo *TRI,
1033 bool IncludeSelf = false)
1034 : RCMaskWords((TRI->getNumRegClasses() + 31) / 32),
1035 Idx(RC->getSuperRegIndices()), Mask(RC->getSubClassMask()) {
1040 /// Returns true if this iterator is still pointing at a valid entry.
1041 bool isValid() const { return Idx; }
1043 /// Returns the current sub-register index.
1044 unsigned getSubReg() const { return SubReg; }
1046 /// Returns the bit mask of register classes that getSubReg() projects into
1048 /// See TargetRegisterClass::getSubClassMask() for how to use it.
1049 const uint32_t *getMask() const { return Mask; }
1051 /// Advance iterator to the next entry.
1053 assert(isValid() && "Cannot move iterator past end.");
1054 Mask += RCMaskWords;
1061 //===----------------------------------------------------------------------===//
1062 // BitMaskClassIterator
1063 //===----------------------------------------------------------------------===//
1064 /// This class encapuslates the logic to iterate over bitmask returned by
1065 /// the various RegClass related APIs.
1066 /// E.g., this class can be used to iterate over the subclasses provided by
1067 /// TargetRegisterClass::getSubClassMask or SuperRegClassIterator::getMask.
1068 class BitMaskClassIterator {
1069 /// Total number of register classes.
1070 const unsigned NumRegClasses;
1071 /// Base index of CurrentChunk.
1072 /// In other words, the number of bit we read to get at the
1073 /// beginning of that chunck.
1075 /// Adjust base index of CurrentChunk.
1076 /// Base index + how many bit we read within CurrentChunk.
1078 /// Current register class ID.
1080 /// Mask we are iterating over.
1081 const uint32_t *Mask;
1082 /// Current chunk of the Mask we are traversing.
1083 uint32_t CurrentChunk;
1085 /// Move ID to the next set bit.
1086 void moveToNextID() {
1087 // If the current chunk of memory is empty, move to the next one,
1088 // while making sure we do not go pass the number of register
1090 while (!CurrentChunk) {
1091 // Move to the next chunk.
1093 if (Base >= NumRegClasses) {
1097 CurrentChunk = *++Mask;
1100 // Otherwise look for the first bit set from the right
1101 // (representation of the class ID is big endian).
1102 // See getSubClassMask for more details on the representation.
1103 unsigned Offset = countTrailingZeros(CurrentChunk);
1104 // Add the Offset to the adjusted base number of this chunk: Idx.
1105 // This is the ID of the register class.
1108 // Consume the zeros, if any, and the bit we just read
1109 // so that we are at the right spot for the next call.
1110 // Do not do Offset + 1 because Offset may be 31 and 32
1111 // will be UB for the shift, though in that case we could
1112 // have make the chunk being equal to 0, but that would
1113 // have introduced a if statement.
1118 /// Move \p NumBits Bits forward in CurrentChunk.
1119 void moveNBits(unsigned NumBits) {
1120 assert(NumBits < 32 && "Undefined behavior spotted!");
1121 // Consume the bit we read for the next call.
1122 CurrentChunk >>= NumBits;
1123 // Adjust the base for the chunk.
1128 /// Create a BitMaskClassIterator that visits all the register classes
1129 /// represented by \p Mask.
1131 /// \pre \p Mask != nullptr
1132 BitMaskClassIterator(const uint32_t *Mask, const TargetRegisterInfo &TRI)
1133 : NumRegClasses(TRI.getNumRegClasses()), Mask(Mask), CurrentChunk(*Mask) {
1134 // Move to the first ID.
1138 /// Returns true if this iterator is still pointing at a valid entry.
1139 bool isValid() const { return getID() != NumRegClasses; }
1141 /// Returns the current register class ID.
1142 unsigned getID() const { return ID; }
1144 /// Advance iterator to the next entry.
1146 assert(isValid() && "Cannot move iterator past end.");
1151 // This is useful when building IndexedMaps keyed on virtual registers
1152 struct VirtReg2IndexFunctor {
1153 using argument_type = unsigned;
1154 unsigned operator()(unsigned Reg) const {
1155 return TargetRegisterInfo::virtReg2Index(Reg);
1159 /// Prints virtual and physical registers with or without a TRI instance.
1162 /// %noreg - NoRegister
1163 /// %5 - a virtual register.
1164 /// %5:sub_8bit - a virtual register with sub-register index (with TRI).
1165 /// %eax - a physical register
1166 /// %physreg17 - a physical register when no TRI instance given.
1168 /// Usage: OS << printReg(Reg, TRI, SubRegIdx) << '\n';
1169 Printable printReg(unsigned Reg, const TargetRegisterInfo *TRI = nullptr,
1170 unsigned SubIdx = 0,
1171 const MachineRegisterInfo *MRI = nullptr);
1173 /// Create Printable object to print register units on a \ref raw_ostream.
1175 /// Register units are named after their root registers:
1177 /// al - Single root.
1178 /// fp0~st7 - Dual roots.
1180 /// Usage: OS << printRegUnit(Unit, TRI) << '\n';
1181 Printable printRegUnit(unsigned Unit, const TargetRegisterInfo *TRI);
1183 /// Create Printable object to print virtual registers and physical
1184 /// registers on a \ref raw_ostream.
1185 Printable printVRegOrUnit(unsigned VRegOrUnit, const TargetRegisterInfo *TRI);
1187 /// Create Printable object to print register classes or register banks
1188 /// on a \ref raw_ostream.
1189 Printable printRegClassOrBank(unsigned Reg, const MachineRegisterInfo &RegInfo,
1190 const TargetRegisterInfo *TRI);
1192 } // end namespace llvm
1194 #endif // LLVM_CODEGEN_TARGETREGISTERINFO_H