1 //===--- BitTracker.h -----------------------------------------------------===//
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 //===----------------------------------------------------------------------===//
13 #include "llvm/ADT/SetVector.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/CodeGen/MachineFunction.h"
23 class MachineRegisterInfo;
24 class MachineBasicBlock;
35 struct MachineEvaluator;
37 typedef SetVector<const MachineBasicBlock *> BranchTargetList;
39 typedef std::map<unsigned, RegisterCell> CellMapType;
41 BitTracker(const MachineEvaluator &E, MachineFunction &F);
45 void trace(bool On = false) { Trace = On; }
46 bool has(unsigned Reg) const;
47 const RegisterCell &lookup(unsigned Reg) const;
48 RegisterCell get(RegisterRef RR) const;
49 void put(RegisterRef RR, const RegisterCell &RC);
50 void subst(RegisterRef OldRR, RegisterRef NewRR);
51 bool reached(const MachineBasicBlock *B) const;
54 void visitPHI(const MachineInstr *PI);
55 void visitNonBranch(const MachineInstr *MI);
56 void visitBranchesFrom(const MachineInstr *BI);
57 void visitUsesOf(unsigned Reg);
60 typedef std::pair<int,int> CFGEdge;
61 typedef std::set<CFGEdge> EdgeSetType;
62 typedef std::set<const MachineInstr *> InstrSetType;
63 typedef std::queue<CFGEdge> EdgeQueueType;
65 EdgeSetType EdgeExec; // Executable flow graph edges.
66 InstrSetType InstrExec; // Executable instructions.
67 EdgeQueueType FlowQ; // Work queue of CFG edges.
68 bool Trace; // Enable tracing for debugging.
70 const MachineEvaluator &ME;
72 MachineRegisterInfo &MRI;
77 // Abstraction of a reference to bit at position Pos from a register Reg.
78 struct BitTracker::BitRef {
79 BitRef(unsigned R = 0, uint16_t P = 0) : Reg(R), Pos(P) {}
80 BitRef(const BitRef &BR) : Reg(BR.Reg), Pos(BR.Pos) {}
81 bool operator== (const BitRef &BR) const {
82 // If Reg is 0, disregard Pos.
83 return Reg == BR.Reg && (Reg == 0 || Pos == BR.Pos);
90 // Abstraction of a register reference in MachineOperand. It contains the
91 // register number and the subregister index.
92 struct BitTracker::RegisterRef {
93 RegisterRef(unsigned R = 0, unsigned S = 0)
95 RegisterRef(const MachineOperand &MO)
96 : Reg(MO.getReg()), Sub(MO.getSubReg()) {}
101 // Value that a single bit can take. This is outside of the context of
102 // any register, it is more of an abstraction of the two-element set of
103 // possible bit values. One extension here is the "Ref" type, which
104 // indicates that this bit takes the same value as the bit described by
106 struct BitTracker::BitValue {
108 Top, // Bit not yet defined.
111 Ref // Bit value same as the one described in RefI.
112 // Conceptually, there is no explicit "bottom" value: the lattice's
113 // bottom will be expressed as a "ref to itself", which, in the context
114 // of registers, could be read as "this value of this bit is defined by
118 // Self <= x, where "Self" is "ref to itself".
119 // This makes the value lattice different for each virtual register
120 // (even for each bit in the same virtual register), since the "bottom"
121 // for one register will be a simple "ref" for another register.
122 // Since we do not store the "Self" bit and register number, the meet
123 // operation will need to take it as a parameter.
125 // In practice there is a special case for values that are not associa-
126 // ted with any specific virtual register. An example would be a value
127 // corresponding to a bit of a physical register, or an intermediate
128 // value obtained in some computation (such as instruction evaluation).
129 // Such cases are identical to the usual Ref type, but the register
130 // number is 0. In such case the Pos field of the reference is ignored.
132 // What is worthy of notice is that in value V (that is a "ref"), as long
133 // as the RefI.Reg is not 0, it may actually be the same register as the
134 // one in which V will be contained. If the RefI.Pos refers to the posi-
135 // tion of V, then V is assumed to be "bottom" (as a "ref to itself"),
136 // otherwise V is taken to be identical to the referenced bit of the
138 // If RefI.Reg is 0, however, such a reference to the same register is
139 // not possible. Any value V that is a "ref", and whose RefI.Reg is 0
140 // is treated as "bottom".
145 BitValue(ValueType T = Top) : Type(T) {}
146 BitValue(bool B) : Type(B ? One : Zero) {}
147 BitValue(const BitValue &V) : Type(V.Type), RefI(V.RefI) {}
148 BitValue(unsigned Reg, uint16_t Pos) : Type(Ref), RefI(Reg, Pos) {}
150 bool operator== (const BitValue &V) const {
153 if (Type == Ref && !(RefI == V.RefI))
157 bool operator!= (const BitValue &V) const {
158 return !operator==(V);
160 bool is(unsigned T) const {
161 assert(T == 0 || T == 1);
162 return T == 0 ? Type == Zero
163 : (T == 1 ? Type == One : false);
166 // The "meet" operation is the "." operation in a semilattice (L, ., T, B):
169 // (3) x.(y.z) = (x.y).z
170 // (4) x.T = x (i.e. T = "top")
171 // (5) x.B = B (i.e. B = "bottom")
173 // This "meet" function will update the value of the "*this" object with
174 // the newly calculated one, and return "true" if the value of *this has
175 // changed, and "false" otherwise.
176 // To prove that it satisfies the conditions (1)-(5), it is sufficient
177 // to show that a relation
178 // x <= y <=> x.y = x
179 // defines a partial order (i.e. that "meet" is same as "infimum").
180 bool meet(const BitValue &V, const BitRef &Self) {
181 // First, check the cases where there is nothing to be done.
182 if (Type == Ref && RefI == Self) // Bottom.meet(V) = Bottom (i.e. This)
184 if (V.Type == Top) // This.meet(Top) = This
186 if (*this == V) // This.meet(This) = This
189 // At this point, we know that the value of "this" will change.
190 // If it is Top, it will become the same as V, otherwise it will
191 // become "bottom" (i.e. Self).
194 RefI = V.RefI; // This may be irrelevant, but copy anyway.
203 // Create a reference to the bit value V.
204 static BitValue ref(const BitValue &V);
206 static BitValue self(const BitRef &Self = BitRef());
209 return Type == Zero || Type == One;
211 operator bool() const {
212 assert(Type == Zero || Type == One);
216 friend raw_ostream &operator<<(raw_ostream &OS, const BitValue &BV);
220 // This operation must be idempotent, i.e. ref(ref(V)) == ref(V).
221 inline BitTracker::BitValue
222 BitTracker::BitValue::ref(const BitValue &V) {
224 return BitValue(V.Type);
226 return BitValue(V.RefI.Reg, V.RefI.Pos);
231 inline BitTracker::BitValue
232 BitTracker::BitValue::self(const BitRef &Self) {
233 return BitValue(Self.Reg, Self.Pos);
237 // A sequence of bits starting from index B up to and including index E.
238 // If E < B, the mask represents two sections: [0..E] and [B..W) where
239 // W is the width of the register.
240 struct BitTracker::BitMask {
241 BitMask() : B(0), E(0) {}
242 BitMask(uint16_t b, uint16_t e) : B(b), E(e) {}
243 uint16_t first() const { return B; }
244 uint16_t last() const { return E; }
250 // Representation of a register: a list of BitValues.
251 struct BitTracker::RegisterCell {
252 RegisterCell(uint16_t Width = DefaultBitN) : Bits(Width) {}
254 uint16_t width() const {
257 const BitValue &operator[](uint16_t BitN) const {
258 assert(BitN < Bits.size());
261 BitValue &operator[](uint16_t BitN) {
262 assert(BitN < Bits.size());
266 bool meet(const RegisterCell &RC, unsigned SelfR);
267 RegisterCell &insert(const RegisterCell &RC, const BitMask &M);
268 RegisterCell extract(const BitMask &M) const; // Returns a new cell.
269 RegisterCell &rol(uint16_t Sh); // Rotate left.
270 RegisterCell &fill(uint16_t B, uint16_t E, const BitValue &V);
271 RegisterCell &cat(const RegisterCell &RC); // Concatenate.
272 uint16_t cl(bool B) const;
273 uint16_t ct(bool B) const;
275 bool operator== (const RegisterCell &RC) const;
276 bool operator!= (const RegisterCell &RC) const {
277 return !operator==(RC);
280 const RegisterCell &operator=(const RegisterCell &RC) {
285 // Generate a "ref" cell for the corresponding register. In the resulting
286 // cell each bit will be described as being the same as the corresponding
287 // bit in register Reg (i.e. the cell is "defined" by register Reg).
288 static RegisterCell self(unsigned Reg, uint16_t Width);
289 // Generate a "top" cell of given size.
290 static RegisterCell top(uint16_t Width);
291 // Generate a cell that is a "ref" to another cell.
292 static RegisterCell ref(const RegisterCell &C);
295 // The DefaultBitN is here only to avoid frequent reallocation of the
296 // memory in the vector.
297 static const unsigned DefaultBitN = 32;
298 typedef SmallVector<BitValue, DefaultBitN> BitValueList;
301 friend raw_ostream &operator<<(raw_ostream &OS, const RegisterCell &RC);
305 inline bool BitTracker::has(unsigned Reg) const {
306 return Map.find(Reg) != Map.end();
310 inline const BitTracker::RegisterCell&
311 BitTracker::lookup(unsigned Reg) const {
312 CellMapType::const_iterator F = Map.find(Reg);
313 assert(F != Map.end());
318 inline BitTracker::RegisterCell
319 BitTracker::RegisterCell::self(unsigned Reg, uint16_t Width) {
320 RegisterCell RC(Width);
321 for (uint16_t i = 0; i < Width; ++i)
322 RC.Bits[i] = BitValue::self(BitRef(Reg, i));
327 inline BitTracker::RegisterCell
328 BitTracker::RegisterCell::top(uint16_t Width) {
329 RegisterCell RC(Width);
330 for (uint16_t i = 0; i < Width; ++i)
331 RC.Bits[i] = BitValue(BitValue::Top);
336 inline BitTracker::RegisterCell
337 BitTracker::RegisterCell::ref(const RegisterCell &C) {
338 uint16_t W = C.width();
340 for (unsigned i = 0; i < W; ++i)
341 RC[i] = BitValue::ref(C[i]);
345 // A class to evaluate target's instructions and update the cell maps.
346 // This is used internally by the bit tracker. A target that wants to
347 // utilize this should implement the evaluation functions (noted below)
348 // in a subclass of this class.
349 struct BitTracker::MachineEvaluator {
350 MachineEvaluator(const TargetRegisterInfo &T, MachineRegisterInfo &M)
352 virtual ~MachineEvaluator() {}
354 uint16_t getRegBitWidth(const RegisterRef &RR) const;
356 RegisterCell getCell(const RegisterRef &RR, const CellMapType &M) const;
357 void putCell(const RegisterRef &RR, RegisterCell RC, CellMapType &M) const;
358 // A result of any operation should use refs to the source cells, not
359 // the cells directly. This function is a convenience wrapper to quickly
360 // generate a ref for a cell corresponding to a register reference.
361 RegisterCell getRef(const RegisterRef &RR, const CellMapType &M) const {
362 RegisterCell RC = getCell(RR, M);
363 return RegisterCell::ref(RC);
367 // Check if a cell is an immediate value (i.e. all bits are either 0 or 1).
368 bool isInt(const RegisterCell &A) const;
369 // Convert cell to an immediate value.
370 uint64_t toInt(const RegisterCell &A) const;
372 // Generate cell from an immediate value.
373 RegisterCell eIMM(int64_t V, uint16_t W) const;
374 RegisterCell eIMM(const ConstantInt *CI) const;
377 RegisterCell eADD(const RegisterCell &A1, const RegisterCell &A2) const;
378 RegisterCell eSUB(const RegisterCell &A1, const RegisterCell &A2) const;
379 RegisterCell eMLS(const RegisterCell &A1, const RegisterCell &A2) const;
380 RegisterCell eMLU(const RegisterCell &A1, const RegisterCell &A2) const;
383 RegisterCell eASL(const RegisterCell &A1, uint16_t Sh) const;
384 RegisterCell eLSR(const RegisterCell &A1, uint16_t Sh) const;
385 RegisterCell eASR(const RegisterCell &A1, uint16_t Sh) const;
388 RegisterCell eAND(const RegisterCell &A1, const RegisterCell &A2) const;
389 RegisterCell eORL(const RegisterCell &A1, const RegisterCell &A2) const;
390 RegisterCell eXOR(const RegisterCell &A1, const RegisterCell &A2) const;
391 RegisterCell eNOT(const RegisterCell &A1) const;
393 // Set bit, clear bit.
394 RegisterCell eSET(const RegisterCell &A1, uint16_t BitN) const;
395 RegisterCell eCLR(const RegisterCell &A1, uint16_t BitN) const;
397 // Count leading/trailing bits (zeros/ones).
398 RegisterCell eCLB(const RegisterCell &A1, bool B, uint16_t W) const;
399 RegisterCell eCTB(const RegisterCell &A1, bool B, uint16_t W) const;
401 // Sign/zero extension.
402 RegisterCell eSXT(const RegisterCell &A1, uint16_t FromN) const;
403 RegisterCell eZXT(const RegisterCell &A1, uint16_t FromN) const;
406 // XTR R,b,e: extract bits from A1 starting at bit b, ending at e-1.
407 // INS R,S,b: take R and replace bits starting from b with S.
408 RegisterCell eXTR(const RegisterCell &A1, uint16_t B, uint16_t E) const;
409 RegisterCell eINS(const RegisterCell &A1, const RegisterCell &A2,
412 // User-provided functions for individual targets:
414 // Return a sub-register mask that indicates which bits in Reg belong
415 // to the subregister Sub. These bits are assumed to be contiguous in
416 // the super-register, and have the same ordering in the sub-register
417 // as in the super-register. It is valid to call this function with
418 // Sub == 0, in this case, the function should return a mask that spans
419 // the entire register Reg (which is what the default implementation
421 virtual BitMask mask(unsigned Reg, unsigned Sub) const;
422 // Indicate whether a given register class should be tracked.
423 virtual bool track(const TargetRegisterClass *RC) const { return true; }
424 // Evaluate a non-branching machine instruction, given the cell map with
425 // the input values. Place the results in the Outputs map. Return "true"
426 // if evaluation succeeded, "false" otherwise.
427 virtual bool evaluate(const MachineInstr *MI, const CellMapType &Inputs,
428 CellMapType &Outputs) const;
429 // Evaluate a branch, given the cell map with the input values. Fill out
430 // a list of all possible branch targets and indicate (through a flag)
431 // whether the branch could fall-through. Return "true" if this information
432 // has been successfully computed, "false" otherwise.
433 virtual bool evaluate(const MachineInstr *BI, const CellMapType &Inputs,
434 BranchTargetList &Targets, bool &FallsThru) const = 0;
436 const TargetRegisterInfo &TRI;
437 MachineRegisterInfo &MRI;
440 } // end namespace llvm