aboutsummaryrefslogtreecommitdiffstats
path: root/include/llvm/CodeGen/CallingConvLower.h
blob: e2b744f08ebb19862e6bb5f335d789a9846a5beb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
//===-- llvm/CallingConvLower.h - Calling Conventions -----------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the CCState and CCValAssign classes, used for lowering
// and implementing calling conventions.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_CALLINGCONVLOWER_H
#define LLVM_CODEGEN_CALLINGCONVLOWER_H

#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/Target/TargetCallingConv.h"

namespace llvm {
class CCState;
class MVT;
class TargetMachine;
class TargetRegisterInfo;

/// CCValAssign - Represent assignment of one arg/retval to a location.
class CCValAssign {
public:
  enum LocInfo {
    Full,      // The value fills the full location.
    SExt,      // The value is sign extended in the location.
    ZExt,      // The value is zero extended in the location.
    AExt,      // The value is extended with undefined upper bits.
    SExtUpper, // The value is in the upper bits of the location and should be
               // sign extended when retrieved.
    ZExtUpper, // The value is in the upper bits of the location and should be
               // zero extended when retrieved.
    AExtUpper, // The value is in the upper bits of the location and should be
               // extended with undefined upper bits when retrieved.
    BCvt,      // The value is bit-converted in the location.
    VExt,      // The value is vector-widened in the location.
               // FIXME: Not implemented yet. Code that uses AExt to mean
               // vector-widen should be fixed to use VExt instead.
    FPExt,     // The floating-point value is fp-extended in the location.
    Indirect   // The location contains pointer to the value.
    // TODO: a subset of the value is in the location.
  };

private:
  /// ValNo - This is the value number begin assigned (e.g. an argument number).
  unsigned ValNo;

  /// Loc is either a stack offset or a register number.
  unsigned Loc;

  /// isMem - True if this is a memory loc, false if it is a register loc.
  unsigned isMem : 1;

  /// isCustom - True if this arg/retval requires special handling.
  unsigned isCustom : 1;

  /// Information about how the value is assigned.
  LocInfo HTP : 6;

  /// ValVT - The type of the value being assigned.
  MVT ValVT;

  /// LocVT - The type of the location being assigned to.
  MVT LocVT;
public:

  static CCValAssign getReg(unsigned ValNo, MVT ValVT,
                            unsigned RegNo, MVT LocVT,
                            LocInfo HTP) {
    CCValAssign Ret;
    Ret.ValNo = ValNo;
    Ret.Loc = RegNo;
    Ret.isMem = false;
    Ret.isCustom = false;
    Ret.HTP = HTP;
    Ret.ValVT = ValVT;
    Ret.LocVT = LocVT;
    return Ret;
  }

  static CCValAssign getCustomReg(unsigned ValNo, MVT ValVT,
                                  unsigned RegNo, MVT LocVT,
                                  LocInfo HTP) {
    CCValAssign Ret;
    Ret = getReg(ValNo, ValVT, RegNo, LocVT, HTP);
    Ret.isCustom = true;
    return Ret;
  }

  static CCValAssign getMem(unsigned ValNo, MVT ValVT,
                            unsigned Offset, MVT LocVT,
                            LocInfo HTP) {
    CCValAssign Ret;
    Ret.ValNo = ValNo;
    Ret.Loc = Offset;
    Ret.isMem = true;
    Ret.isCustom = false;
    Ret.HTP = HTP;
    Ret.ValVT = ValVT;
    Ret.LocVT = LocVT;
    return Ret;
  }

  static CCValAssign getCustomMem(unsigned ValNo, MVT ValVT,
                                  unsigned Offset, MVT LocVT,
                                  LocInfo HTP) {
    CCValAssign Ret;
    Ret = getMem(ValNo, ValVT, Offset, LocVT, HTP);
    Ret.isCustom = true;
    return Ret;
  }

  // There is no need to differentiate between a pending CCValAssign and other
  // kinds, as they are stored in a different list.
  static CCValAssign getPending(unsigned ValNo, MVT ValVT, MVT LocVT,
                                LocInfo HTP, unsigned ExtraInfo = 0) {
    return getReg(ValNo, ValVT, ExtraInfo, LocVT, HTP);
  }

  void convertToReg(unsigned RegNo) {
    Loc = RegNo;
    isMem = false;
  }

  void convertToMem(unsigned Offset) {
    Loc = Offset;
    isMem = true;
  }

  unsigned getValNo() const { return ValNo; }
  MVT getValVT() const { return ValVT; }

  bool isRegLoc() const { return !isMem; }
  bool isMemLoc() const { return isMem; }

  bool needsCustom() const { return isCustom; }

  unsigned getLocReg() const { assert(isRegLoc()); return Loc; }
  unsigned getLocMemOffset() const { assert(isMemLoc()); return Loc; }
  unsigned getExtraInfo() const { return Loc; }
  MVT getLocVT() const { return LocVT; }

  LocInfo getLocInfo() const { return HTP; }
  bool isExtInLoc() const {
    return (HTP == AExt || HTP == SExt || HTP == ZExt);
  }

  bool isUpperBitsInLoc() const {
    return HTP == AExtUpper || HTP == SExtUpper || HTP == ZExtUpper;
  }
};

/// Describes a register that needs to be forwarded from the prologue to a
/// musttail call.
struct ForwardedRegister {
  ForwardedRegister(unsigned VReg, MCPhysReg PReg, MVT VT)
      : VReg(VReg), PReg(PReg), VT(VT) {}
  unsigned VReg;
  MCPhysReg PReg;
  MVT VT;
};

/// CCAssignFn - This function assigns a location for Val, updating State to
/// reflect the change.  It returns 'true' if it failed to handle Val.
typedef bool CCAssignFn(unsigned ValNo, MVT ValVT,
                        MVT LocVT, CCValAssign::LocInfo LocInfo,
                        ISD::ArgFlagsTy ArgFlags, CCState &State);

/// CCCustomFn - This function assigns a location for Val, possibly updating
/// all args to reflect changes and indicates if it handled it. It must set
/// isCustom if it handles the arg and returns true.
typedef bool CCCustomFn(unsigned &ValNo, MVT &ValVT,
                        MVT &LocVT, CCValAssign::LocInfo &LocInfo,
                        ISD::ArgFlagsTy &ArgFlags, CCState &State);

/// ParmContext - This enum tracks whether calling convention lowering is in
/// the context of prologue or call generation. Not all backends make use of
/// this information.
typedef enum { Unknown, Prologue, Call } ParmContext;

/// CCState - This class holds information needed while lowering arguments and
/// return values.  It captures which registers are already assigned and which
/// stack slots are used.  It provides accessors to allocate these values.
class CCState {
private:
  CallingConv::ID CallingConv;
  bool IsVarArg;
  MachineFunction &MF;
  const TargetRegisterInfo &TRI;
  SmallVectorImpl<CCValAssign> &Locs;
  LLVMContext &Context;

  unsigned StackOffset;
  SmallVector<uint32_t, 16> UsedRegs;
  SmallVector<CCValAssign, 4> PendingLocs;

  // ByValInfo and SmallVector<ByValInfo, 4> ByValRegs:
  //
  // Vector of ByValInfo instances (ByValRegs) is introduced for byval registers
  // tracking.
  // Or, in another words it tracks byval parameters that are stored in
  // general purpose registers.
  //
  // For 4 byte stack alignment,
  // instance index means byval parameter number in formal
  // arguments set. Assume, we have some "struct_type" with size = 4 bytes,
  // then, for function "foo":
  //
  // i32 foo(i32 %p, %struct_type* %r, i32 %s, %struct_type* %t)
  //
  // ByValRegs[0] describes how "%r" is stored (Begin == r1, End == r2)
  // ByValRegs[1] describes how "%t" is stored (Begin == r3, End == r4).
  //
  // In case of 8 bytes stack alignment,
  // ByValRegs may also contain information about wasted registers.
  // In function shown above, r3 would be wasted according to AAPCS rules.
  // And in that case ByValRegs[1].Waste would be "true".
  // ByValRegs vector size still would be 2,
  // while "%t" goes to the stack: it wouldn't be described in ByValRegs.
  //
  // Supposed use-case for this collection:
  // 1. Initially ByValRegs is empty, InRegsParamsProcessed is 0.
  // 2. HandleByVal fillups ByValRegs.
  // 3. Argument analysis (LowerFormatArguments, for example). After
  // some byval argument was analyzed, InRegsParamsProcessed is increased.
  struct ByValInfo {
    ByValInfo(unsigned B, unsigned E, bool IsWaste = false) :
      Begin(B), End(E), Waste(IsWaste) {}
    // First register allocated for current parameter.
    unsigned Begin;

    // First after last register allocated for current parameter.
    unsigned End;

    // Means that current range of registers doesn't belong to any
    // parameters. It was wasted due to stack alignment rules.
    // For more information see:
    // AAPCS, 5.5 Parameter Passing, Stage C, C.3.
    bool Waste;
  };
  SmallVector<ByValInfo, 4 > ByValRegs;

  // InRegsParamsProcessed - shows how many instances of ByValRegs was proceed
  // during argument analysis.
  unsigned InRegsParamsProcessed;

protected:
  ParmContext CallOrPrologue;

public:
  CCState(CallingConv::ID CC, bool isVarArg, MachineFunction &MF,
          SmallVectorImpl<CCValAssign> &locs, LLVMContext &C);

  void addLoc(const CCValAssign &V) {
    Locs.push_back(V);
  }

  LLVMContext &getContext() const { return Context; }
  MachineFunction &getMachineFunction() const { return MF; }
  CallingConv::ID getCallingConv() const { return CallingConv; }
  bool isVarArg() const { return IsVarArg; }

  unsigned getNextStackOffset() const { return StackOffset; }

  /// isAllocated - Return true if the specified register (or an alias) is
  /// allocated.
  bool isAllocated(unsigned Reg) const {
    return UsedRegs[Reg/32] & (1 << (Reg&31));
  }

  /// AnalyzeFormalArguments - Analyze an array of argument values,
  /// incorporating info about the formals into this state.
  void AnalyzeFormalArguments(const SmallVectorImpl<ISD::InputArg> &Ins,
                              CCAssignFn Fn);

  /// AnalyzeReturn - Analyze the returned values of a return,
  /// incorporating info about the result values into this state.
  void AnalyzeReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
                     CCAssignFn Fn);

  /// CheckReturn - Analyze the return values of a function, returning
  /// true if the return can be performed without sret-demotion, and
  /// false otherwise.
  bool CheckReturn(const SmallVectorImpl<ISD::OutputArg> &ArgsFlags,
                   CCAssignFn Fn);

  /// AnalyzeCallOperands - Analyze the outgoing arguments to a call,
  /// incorporating info about the passed values into this state.
  void AnalyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
                           CCAssignFn Fn);

  /// AnalyzeCallOperands - Same as above except it takes vectors of types
  /// and argument flags.
  void AnalyzeCallOperands(SmallVectorImpl<MVT> &ArgVTs,
                           SmallVectorImpl<ISD::ArgFlagsTy> &Flags,
                           CCAssignFn Fn);

  /// AnalyzeCallResult - Analyze the return values of a call,
  /// incorporating info about the passed values into this state.
  void AnalyzeCallResult(const SmallVectorImpl<ISD::InputArg> &Ins,
                         CCAssignFn Fn);

  /// AnalyzeCallResult - Same as above except it's specialized for calls which
  /// produce a single value.
  void AnalyzeCallResult(MVT VT, CCAssignFn Fn);

  /// getFirstUnallocated - Return the index of the first unallocated register
  /// in the set, or Regs.size() if they are all allocated.
  unsigned getFirstUnallocated(ArrayRef<MCPhysReg> Regs) const {
    for (unsigned i = 0; i < Regs.size(); ++i)
      if (!isAllocated(Regs[i]))
        return i;
    return Regs.size();
  }

  /// AllocateReg - Attempt to allocate one register.  If it is not available,
  /// return zero.  Otherwise, return the register, marking it and any aliases
  /// as allocated.
  unsigned AllocateReg(unsigned Reg) {
    if (isAllocated(Reg)) return 0;
    MarkAllocated(Reg);
    return Reg;
  }

  /// Version of AllocateReg with extra register to be shadowed.
  unsigned AllocateReg(unsigned Reg, unsigned ShadowReg) {
    if (isAllocated(Reg)) return 0;
    MarkAllocated(Reg);
    MarkAllocated(ShadowReg);
    return Reg;
  }

  /// AllocateReg - Attempt to allocate one of the specified registers.  If none
  /// are available, return zero.  Otherwise, return the first one available,
  /// marking it and any aliases as allocated.
  unsigned AllocateReg(ArrayRef<MCPhysReg> Regs) {
    unsigned FirstUnalloc = getFirstUnallocated(Regs);
    if (FirstUnalloc == Regs.size())
      return 0;    // Didn't find the reg.

    // Mark the register and any aliases as allocated.
    unsigned Reg = Regs[FirstUnalloc];
    MarkAllocated(Reg);
    return Reg;
  }

  /// AllocateRegBlock - Attempt to allocate a block of RegsRequired consecutive
  /// registers. If this is not possible, return zero. Otherwise, return the first
  /// register of the block that were allocated, marking the entire block as allocated.
  unsigned AllocateRegBlock(ArrayRef<uint16_t> Regs, unsigned RegsRequired) {
    if (RegsRequired > Regs.size())
      return 0;

    for (unsigned StartIdx = 0; StartIdx <= Regs.size() - RegsRequired;
         ++StartIdx) {
      bool BlockAvailable = true;
      // Check for already-allocated regs in this block
      for (unsigned BlockIdx = 0; BlockIdx < RegsRequired; ++BlockIdx) {
        if (isAllocated(Regs[StartIdx + BlockIdx])) {
          BlockAvailable = false;
          break;
        }
      }
      if (BlockAvailable) {
        // Mark the entire block as allocated
        for (unsigned BlockIdx = 0; BlockIdx < RegsRequired; ++BlockIdx) {
          MarkAllocated(Regs[StartIdx + BlockIdx]);
        }
        return Regs[StartIdx];
      }
    }
    // No block was available
    return 0;
  }

  /// Version of AllocateReg with list of registers to be shadowed.
  unsigned AllocateReg(ArrayRef<MCPhysReg> Regs, const MCPhysReg *ShadowRegs) {
    unsigned FirstUnalloc = getFirstUnallocated(Regs);
    if (FirstUnalloc == Regs.size())
      return 0;    // Didn't find the reg.

    // Mark the register and any aliases as allocated.
    unsigned Reg = Regs[FirstUnalloc], ShadowReg = ShadowRegs[FirstUnalloc];
    MarkAllocated(Reg);
    MarkAllocated(ShadowReg);
    return Reg;
  }

  /// AllocateStack - Allocate a chunk of stack space with the specified size
  /// and alignment.
  unsigned AllocateStack(unsigned Size, unsigned Align) {
    assert(Align && ((Align - 1) & Align) == 0); // Align is power of 2.
    StackOffset = ((StackOffset + Align - 1) & ~(Align - 1));
    unsigned Result = StackOffset;
    StackOffset += Size;
    MF.getFrameInfo()->ensureMaxAlignment(Align);
    return Result;
  }

  /// Version of AllocateStack with extra register to be shadowed.
  unsigned AllocateStack(unsigned Size, unsigned Align, unsigned ShadowReg) {
    MarkAllocated(ShadowReg);
    return AllocateStack(Size, Align);
  }

  /// Version of AllocateStack with list of extra registers to be shadowed.
  /// Note that, unlike AllocateReg, this shadows ALL of the shadow registers.
  unsigned AllocateStack(unsigned Size, unsigned Align,
                         ArrayRef<MCPhysReg> ShadowRegs) {
    for (unsigned i = 0; i < ShadowRegs.size(); ++i)
      MarkAllocated(ShadowRegs[i]);
    return AllocateStack(Size, Align);
  }

  // HandleByVal - Allocate a stack slot large enough to pass an argument by
  // value. The size and alignment information of the argument is encoded in its
  // parameter attribute.
  void HandleByVal(unsigned ValNo, MVT ValVT,
                   MVT LocVT, CCValAssign::LocInfo LocInfo,
                   int MinSize, int MinAlign, ISD::ArgFlagsTy ArgFlags);

  // Returns count of byval arguments that are to be stored (even partly)
  // in registers.
  unsigned getInRegsParamsCount() const { return ByValRegs.size(); }

  // Returns count of byval in-regs arguments proceed.
  unsigned getInRegsParamsProcessed() const { return InRegsParamsProcessed; }

  // Get information about N-th byval parameter that is stored in registers.
  // Here "ByValParamIndex" is N.
  void getInRegsParamInfo(unsigned InRegsParamRecordIndex,
                          unsigned& BeginReg, unsigned& EndReg) const {
    assert(InRegsParamRecordIndex < ByValRegs.size() &&
           "Wrong ByVal parameter index");

    const ByValInfo& info = ByValRegs[InRegsParamRecordIndex];
    BeginReg = info.Begin;
    EndReg = info.End;
  }

  // Add information about parameter that is kept in registers.
  void addInRegsParamInfo(unsigned RegBegin, unsigned RegEnd) {
    ByValRegs.push_back(ByValInfo(RegBegin, RegEnd));
  }

  // Goes either to next byval parameter (excluding "waste" record), or
  // to the end of collection.
  // Returns false, if end is reached.
  bool nextInRegsParam() {
    unsigned e = ByValRegs.size();
    if (InRegsParamsProcessed < e)
      ++InRegsParamsProcessed;
    return InRegsParamsProcessed < e;
  }

  // Clear byval registers tracking info.
  void clearByValRegsInfo() {
    InRegsParamsProcessed = 0;
    ByValRegs.clear();
  }

  // Rewind byval registers tracking info.
  void rewindByValRegsInfo() {
    InRegsParamsProcessed = 0;
  }

  ParmContext getCallOrPrologue() const { return CallOrPrologue; }

  // Get list of pending assignments
  SmallVectorImpl<llvm::CCValAssign> &getPendingLocs() {
    return PendingLocs;
  }

  /// Compute the remaining unused register parameters that would be used for
  /// the given value type. This is useful when varargs are passed in the
  /// registers that normal prototyped parameters would be passed in, or for
  /// implementing perfect forwarding.
  void getRemainingRegParmsForType(SmallVectorImpl<MCPhysReg> &Regs, MVT VT,
                                   CCAssignFn Fn);

  /// Compute the set of registers that need to be preserved and forwarded to
  /// any musttail calls.
  void analyzeMustTailForwardedRegisters(
      SmallVectorImpl<ForwardedRegister> &Forwards, ArrayRef<MVT> RegParmTypes,
      CCAssignFn Fn);

private:
  /// MarkAllocated - Mark a register and all of its aliases as allocated.
  void MarkAllocated(unsigned Reg);
};



} // end namespace llvm

#endif