This file is indexed.

/usr/include/llvm-3.9/llvm/Target/TargetFrameLowering.h is in llvm-3.9-dev 1:3.9.1-19ubuntu1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  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
//===-- llvm/Target/TargetFrameLowering.h ---------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Interface to describe the layout of a stack frame on the target machine.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TARGET_TARGETFRAMELOWERING_H
#define LLVM_TARGET_TARGETFRAMELOWERING_H

#include "llvm/CodeGen/MachineBasicBlock.h"
#include <utility>
#include <vector>

namespace llvm {
  class BitVector;
  class CalleeSavedInfo;
  class MachineFunction;
  class RegScavenger;

/// Information about stack frame layout on the target.  It holds the direction
/// of stack growth, the known stack alignment on entry to each function, and
/// the offset to the locals area.
///
/// The offset to the local area is the offset from the stack pointer on
/// function entry to the first location where function data (local variables,
/// spill locations) can be stored.
class TargetFrameLowering {
public:
  enum StackDirection {
    StackGrowsUp,        // Adding to the stack increases the stack address
    StackGrowsDown       // Adding to the stack decreases the stack address
  };

  // Maps a callee saved register to a stack slot with a fixed offset.
  struct SpillSlot {
    unsigned Reg;
    int Offset; // Offset relative to stack pointer on function entry.
  };
private:
  StackDirection StackDir;
  unsigned StackAlignment;
  unsigned TransientStackAlignment;
  int LocalAreaOffset;
  bool StackRealignable;
public:
  TargetFrameLowering(StackDirection D, unsigned StackAl, int LAO,
                      unsigned TransAl = 1, bool StackReal = true)
    : StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
      LocalAreaOffset(LAO), StackRealignable(StackReal) {}

  virtual ~TargetFrameLowering();

  // These methods return information that describes the abstract stack layout
  // of the target machine.

  /// getStackGrowthDirection - Return the direction the stack grows
  ///
  StackDirection getStackGrowthDirection() const { return StackDir; }

  /// getStackAlignment - This method returns the number of bytes to which the
  /// stack pointer must be aligned on entry to a function.  Typically, this
  /// is the largest alignment for any data object in the target.
  ///
  unsigned getStackAlignment() const { return StackAlignment; }

  /// alignSPAdjust - This method aligns the stack adjustment to the correct
  /// alignment.
  ///
  int alignSPAdjust(int SPAdj) const {
    if (SPAdj < 0) {
      SPAdj = -alignTo(-SPAdj, StackAlignment);
    } else {
      SPAdj = alignTo(SPAdj, StackAlignment);
    }
    return SPAdj;
  }

  /// getTransientStackAlignment - This method returns the number of bytes to
  /// which the stack pointer must be aligned at all times, even between
  /// calls.
  ///
  unsigned getTransientStackAlignment() const {
    return TransientStackAlignment;
  }

  /// isStackRealignable - This method returns whether the stack can be
  /// realigned.
  bool isStackRealignable() const {
    return StackRealignable;
  }

  /// Return the skew that has to be applied to stack alignment under
  /// certain conditions (e.g. stack was adjusted before function \p MF
  /// was called).
  virtual unsigned getStackAlignmentSkew(const MachineFunction &MF) const;

  /// getOffsetOfLocalArea - This method returns the offset of the local area
  /// from the stack pointer on entrance to a function.
  ///
  int getOffsetOfLocalArea() const { return LocalAreaOffset; }

  /// isFPCloseToIncomingSP - Return true if the frame pointer is close to
  /// the incoming stack pointer, false if it is close to the post-prologue
  /// stack pointer.
  virtual bool isFPCloseToIncomingSP() const { return true; }

  /// assignCalleeSavedSpillSlots - Allows target to override spill slot
  /// assignment logic.  If implemented, assignCalleeSavedSpillSlots() should
  /// assign frame slots to all CSI entries and return true.  If this method
  /// returns false, spill slots will be assigned using generic implementation.
  /// assignCalleeSavedSpillSlots() may add, delete or rearrange elements of
  /// CSI.
  virtual bool
  assignCalleeSavedSpillSlots(MachineFunction &MF,
                              const TargetRegisterInfo *TRI,
                              std::vector<CalleeSavedInfo> &CSI) const {
    return false;
  }

  /// getCalleeSavedSpillSlots - This method returns a pointer to an array of
  /// pairs, that contains an entry for each callee saved register that must be
  /// spilled to a particular stack location if it is spilled.
  ///
  /// Each entry in this array contains a <register,offset> pair, indicating the
  /// fixed offset from the incoming stack pointer that each register should be
  /// spilled at. If a register is not listed here, the code generator is
  /// allowed to spill it anywhere it chooses.
  ///
  virtual const SpillSlot *
  getCalleeSavedSpillSlots(unsigned &NumEntries) const {
    NumEntries = 0;
    return nullptr;
  }

  /// targetHandlesStackFrameRounding - Returns true if the target is
  /// responsible for rounding up the stack frame (probably at emitPrologue
  /// time).
  virtual bool targetHandlesStackFrameRounding() const {
    return false;
  }

  /// Returns true if the target will correctly handle shrink wrapping.
  virtual bool enableShrinkWrapping(const MachineFunction &MF) const {
    return false;
  }

  /// Returns true if the stack slot holes in the fixed and callee-save stack
  /// area should be used when allocating other stack locations to reduce stack
  /// size.
  virtual bool enableStackSlotScavenging(const MachineFunction &MF) const {
    return false;
  }

  /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
  /// the function.
  virtual void emitPrologue(MachineFunction &MF,
                            MachineBasicBlock &MBB) const = 0;
  virtual void emitEpilogue(MachineFunction &MF,
                            MachineBasicBlock &MBB) const = 0;

  /// Replace a StackProbe stub (if any) with the actual probe code inline
  virtual void inlineStackProbe(MachineFunction &MF,
                                MachineBasicBlock &PrologueMBB) const {}

  /// Adjust the prologue to have the function use segmented stacks. This works
  /// by adding a check even before the "normal" function prologue.
  virtual void adjustForSegmentedStacks(MachineFunction &MF,
                                        MachineBasicBlock &PrologueMBB) const {}

  /// Adjust the prologue to add Erlang Run-Time System (ERTS) specific code in
  /// the assembly prologue to explicitly handle the stack.
  virtual void adjustForHiPEPrologue(MachineFunction &MF,
                                     MachineBasicBlock &PrologueMBB) const {}

  /// Adjust the prologue to add an allocation at a fixed offset from the frame
  /// pointer.
  virtual void
  adjustForFrameAllocatePrologue(MachineFunction &MF,
                                 MachineBasicBlock &PrologueMBB) const {}

  /// spillCalleeSavedRegisters - Issues instruction(s) to spill all callee
  /// saved registers and returns true if it isn't possible / profitable to do
  /// so by issuing a series of store instructions via
  /// storeRegToStackSlot(). Returns false otherwise.
  virtual bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
                                         MachineBasicBlock::iterator MI,
                                        const std::vector<CalleeSavedInfo> &CSI,
                                         const TargetRegisterInfo *TRI) const {
    return false;
  }

  /// restoreCalleeSavedRegisters - Issues instruction(s) to restore all callee
  /// saved registers and returns true if it isn't possible / profitable to do
  /// so by issuing a series of load instructions via loadRegToStackSlot().
  /// Returns false otherwise.
  virtual bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
                                           MachineBasicBlock::iterator MI,
                                        const std::vector<CalleeSavedInfo> &CSI,
                                        const TargetRegisterInfo *TRI) const {
    return false;
  }

  /// Return true if the target needs to disable frame pointer elimination.
  virtual bool noFramePointerElim(const MachineFunction &MF) const;

  /// hasFP - Return true if the specified function should have a dedicated
  /// frame pointer register. For most targets this is true only if the function
  /// has variable sized allocas or if frame pointer elimination is disabled.
  virtual bool hasFP(const MachineFunction &MF) const = 0;

  /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
  /// not required, we reserve argument space for call sites in the function
  /// immediately on entry to the current function. This eliminates the need for
  /// add/sub sp brackets around call sites. Returns true if the call frame is
  /// included as part of the stack frame.
  virtual bool hasReservedCallFrame(const MachineFunction &MF) const {
    return !hasFP(MF);
  }

  /// canSimplifyCallFramePseudos - When possible, it's best to simplify the
  /// call frame pseudo ops before doing frame index elimination. This is
  /// possible only when frame index references between the pseudos won't
  /// need adjusting for the call frame adjustments. Normally, that's true
  /// if the function has a reserved call frame or a frame pointer. Some
  /// targets (Thumb2, for example) may have more complicated criteria,
  /// however, and can override this behavior.
  virtual bool canSimplifyCallFramePseudos(const MachineFunction &MF) const {
    return hasReservedCallFrame(MF) || hasFP(MF);
  }

  // needsFrameIndexResolution - Do we need to perform FI resolution for
  // this function. Normally, this is required only when the function
  // has any stack objects. However, targets may want to override this.
  virtual bool needsFrameIndexResolution(const MachineFunction &MF) const;

  /// getFrameIndexReference - This method should return the base register
  /// and offset used to reference a frame index location. The offset is
  /// returned directly, and the base register is returned via FrameReg.
  virtual int getFrameIndexReference(const MachineFunction &MF, int FI,
                                     unsigned &FrameReg) const;

  /// Same as \c getFrameIndexReference, except that the stack pointer (as
  /// opposed to the frame pointer) will be the preferred value for \p
  /// FrameReg. This is generally used for emitting statepoint or EH tables that
  /// use offsets from RSP.  If \p IgnoreSPUpdates is true, the returned
  /// offset is only guaranteed to be valid with respect to the value of SP at
  /// the end of the prologue.
  virtual int getFrameIndexReferencePreferSP(const MachineFunction &MF, int FI,
                                             unsigned &FrameReg,
                                             bool IgnoreSPUpdates) const {
    // Always safe to dispatch to getFrameIndexReference.
    return getFrameIndexReference(MF, FI, FrameReg);
  }

  /// This method determines which of the registers reported by
  /// TargetRegisterInfo::getCalleeSavedRegs() should actually get saved.
  /// The default implementation checks populates the \p SavedRegs bitset with
  /// all registers which are modified in the function, targets may override
  /// this function to save additional registers.
  /// This method also sets up the register scavenger ensuring there is a free
  /// register or a frameindex available.
  virtual void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
                                    RegScavenger *RS = nullptr) const;

  /// processFunctionBeforeFrameFinalized - This method is called immediately
  /// before the specified function's frame layout (MF.getFrameInfo()) is
  /// finalized.  Once the frame is finalized, MO_FrameIndex operands are
  /// replaced with direct constants.  This method is optional.
  ///
  virtual void processFunctionBeforeFrameFinalized(MachineFunction &MF,
                                             RegScavenger *RS = nullptr) const {
  }

  virtual unsigned getWinEHParentFrameOffset(const MachineFunction &MF) const {
    report_fatal_error("WinEH not implemented for this target");
  }

  /// This method is called during prolog/epilog code insertion to eliminate
  /// call frame setup and destroy pseudo instructions (but only if the Target
  /// is using them).  It is responsible for eliminating these instructions,
  /// replacing them with concrete instructions.  This method need only be
  /// implemented if using call frame setup/destroy pseudo instructions.
  /// Returns an iterator pointing to the instruction after the replaced one.
  virtual MachineBasicBlock::iterator
  eliminateCallFramePseudoInstr(MachineFunction &MF,
                                MachineBasicBlock &MBB,
                                MachineBasicBlock::iterator MI) const {
    llvm_unreachable("Call Frame Pseudo Instructions do not exist on this "
                     "target!");
  }


  /// Order the symbols in the local stack frame.
  /// The list of objects that we want to order is in \p objectsToAllocate as
  /// indices into the MachineFrameInfo. The array can be reordered in any way
  /// upon return. The contents of the array, however, may not be modified (i.e.
  /// only their order may be changed).
  /// By default, just maintain the original order.
  virtual void
  orderFrameObjects(const MachineFunction &MF,
                    SmallVectorImpl<int> &objectsToAllocate) const {
  }

  /// Check whether or not the given \p MBB can be used as a prologue
  /// for the target.
  /// The prologue will be inserted first in this basic block.
  /// This method is used by the shrink-wrapping pass to decide if
  /// \p MBB will be correctly handled by the target.
  /// As soon as the target enable shrink-wrapping without overriding
  /// this method, we assume that each basic block is a valid
  /// prologue.
  virtual bool canUseAsPrologue(const MachineBasicBlock &MBB) const {
    return true;
  }

  /// Check whether or not the given \p MBB can be used as a epilogue
  /// for the target.
  /// The epilogue will be inserted before the first terminator of that block.
  /// This method is used by the shrink-wrapping pass to decide if
  /// \p MBB will be correctly handled by the target.
  /// As soon as the target enable shrink-wrapping without overriding
  /// this method, we assume that each basic block is a valid
  /// epilogue.
  virtual bool canUseAsEpilogue(const MachineBasicBlock &MBB) const {
    return true;
  }

  /// Check if given function is safe for not having callee saved registers.
  /// This is used when interprocedural register allocation is enabled.
  static bool isSafeForNoCSROpt(const Function *F) {
    if (!F->hasLocalLinkage() || F->hasAddressTaken() ||
        !F->hasFnAttribute(Attribute::NoRecurse))
      return false;
    // Function should not be optimized as tail call.
    for (const User *U : F->users())
      if (auto CS = ImmutableCallSite(U))
        if (CS.isTailCall())
          return false;
    return true;
  }
};

} // End llvm namespace

#endif