LLVM  10.0.0svn
MachineFrameInfo.cpp
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1 //===-- MachineFrameInfo.cpp ---------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 /// \file Implements MachineFrameInfo that manages the stack frame.
10 //
11 //===----------------------------------------------------------------------===//
12 
14 
15 #include "llvm/ADT/BitVector.h"
22 #include "llvm/Config/llvm-config.h"
23 #include "llvm/Support/Debug.h"
25 #include <cassert>
26 
27 #define DEBUG_TYPE "codegen"
28 
29 using namespace llvm;
30 
32  if (!StackRealignable)
33  assert(Align <= StackAlignment &&
34  "For targets without stack realignment, Align is out of limit!");
35  if (MaxAlignment < Align) MaxAlignment = Align;
36 }
37 
38 /// Clamp the alignment if requested and emit a warning.
39 static inline llvm::Align clampStackAlignment(bool ShouldClamp,
41  llvm::Align StackAlign) {
42  if (!ShouldClamp || Align <= StackAlign)
43  return Align;
44  LLVM_DEBUG(dbgs() << "Warning: requested alignment " << Align.value()
45  << " exceeds the stack alignment " << StackAlign.value()
46  << " when stack realignment is off" << '\n');
47  return StackAlign;
48 }
49 
51  bool IsSpillSlot,
52  const AllocaInst *Alloca,
53  uint8_t StackID) {
54  assert(Size != 0 && "Cannot allocate zero size stack objects!");
55  Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
56  Objects.push_back(StackObject(Size, Alignment, 0, false, IsSpillSlot, Alloca,
57  !IsSpillSlot, StackID));
58  int Index = (int)Objects.size() - NumFixedObjects - 1;
59  assert(Index >= 0 && "Bad frame index!");
60  if (StackID == 0)
61  ensureMaxAlignment(Alignment);
62  return Index;
63 }
64 
66  llvm::Align Alignment) {
67  Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
68  CreateStackObject(Size, Alignment, true);
69  int Index = (int)Objects.size() - NumFixedObjects - 1;
70  ensureMaxAlignment(Alignment);
71  return Index;
72 }
73 
75  const AllocaInst *Alloca) {
76  HasVarSizedObjects = true;
77  Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
78  Objects.push_back(StackObject(0, Alignment, 0, false, false, Alloca, true));
79  ensureMaxAlignment(Alignment);
80  return (int)Objects.size()-NumFixedObjects-1;
81 }
82 
83 int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset,
84  bool IsImmutable, bool IsAliased) {
85  assert(Size != 0 && "Cannot allocate zero size fixed stack objects!");
86  // The alignment of the frame index can be determined from its offset from
87  // the incoming frame position. If the frame object is at offset 32 and
88  // the stack is guaranteed to be 16-byte aligned, then we know that the
89  // object is 16-byte aligned. Note that unlike the non-fixed case, if the
90  // stack needs realignment, we can't assume that the stack will in fact be
91  // aligned.
92  llvm::Align Alignment =
93  commonAlignment(ForcedRealign ? llvm::Align() : StackAlignment, SPOffset);
94  Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
95  Objects.insert(Objects.begin(),
96  StackObject(Size, Alignment, SPOffset, IsImmutable,
97  /*IsSpillSlot=*/false, /*Alloca=*/nullptr,
98  IsAliased));
99  return -++NumFixedObjects;
100 }
101 
103  int64_t SPOffset,
104  bool IsImmutable) {
105  llvm::Align Alignment =
106  commonAlignment(ForcedRealign ? llvm::Align() : StackAlignment, SPOffset);
107  Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
108  Objects.insert(Objects.begin(),
109  StackObject(Size, Alignment, SPOffset, IsImmutable,
110  /*IsSpillSlot=*/true, /*Alloca=*/nullptr,
111  /*IsAliased=*/false));
112  return -++NumFixedObjects;
113 }
114 
117  BitVector BV(TRI->getNumRegs());
118 
119  // Before CSI is calculated, no registers are considered pristine. They can be
120  // freely used and PEI will make sure they are saved.
121  if (!isCalleeSavedInfoValid())
122  return BV;
123 
124  const MachineRegisterInfo &MRI = MF.getRegInfo();
125  for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR;
126  ++CSR)
127  BV.set(*CSR);
128 
129  // Saved CSRs are not pristine.
130  for (auto &I : getCalleeSavedInfo())
131  for (MCSubRegIterator S(I.getReg(), TRI, true); S.isValid(); ++S)
132  BV.reset(*S);
133 
134  return BV;
135 }
136 
139  const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
140  unsigned MaxAlign = getMaxAlignment();
141  int Offset = 0;
142 
143  // This code is very, very similar to PEI::calculateFrameObjectOffsets().
144  // It really should be refactored to share code. Until then, changes
145  // should keep in mind that there's tight coupling between the two.
146 
147  for (int i = getObjectIndexBegin(); i != 0; ++i) {
148  // Only estimate stack size of default stack.
150  continue;
151  int FixedOff = -getObjectOffset(i);
152  if (FixedOff > Offset) Offset = FixedOff;
153  }
154  for (unsigned i = 0, e = getObjectIndexEnd(); i != e; ++i) {
155  // Only estimate stack size of live objects on default stack.
157  continue;
158  Offset += getObjectSize(i);
159  unsigned Align = getObjectAlignment(i);
160  // Adjust to alignment boundary
161  Offset = (Offset+Align-1)/Align*Align;
162 
163  MaxAlign = std::max(Align, MaxAlign);
164  }
165 
166  if (adjustsStack() && TFI->hasReservedCallFrame(MF))
167  Offset += getMaxCallFrameSize();
168 
169  // Round up the size to a multiple of the alignment. If the function has
170  // any calls or alloca's, align to the target's StackAlignment value to
171  // ensure that the callee's frame or the alloca data is suitably aligned;
172  // otherwise, for leaf functions, align to the TransientStackAlignment
173  // value.
174  unsigned StackAlign;
175  if (adjustsStack() || hasVarSizedObjects() ||
176  (RegInfo->needsStackRealignment(MF) && getObjectIndexEnd() != 0))
177  StackAlign = TFI->getStackAlignment();
178  else
179  StackAlign = TFI->getTransientStackAlignment();
180 
181  // If the frame pointer is eliminated, all frame offsets will be relative to
182  // SP not FP. Align to MaxAlign so this works.
183  StackAlign = std::max(StackAlign, MaxAlign);
184  unsigned AlignMask = StackAlign - 1;
185  Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
186 
187  return (unsigned)Offset;
188 }
189 
191  const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
192  unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode();
193  unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
194  assert(FrameSetupOpcode != ~0u && FrameDestroyOpcode != ~0u &&
195  "Can only compute MaxCallFrameSize if Setup/Destroy opcode are known");
196 
197  MaxCallFrameSize = 0;
198  for (const MachineBasicBlock &MBB : MF) {
199  for (const MachineInstr &MI : MBB) {
200  unsigned Opcode = MI.getOpcode();
201  if (Opcode == FrameSetupOpcode || Opcode == FrameDestroyOpcode) {
202  unsigned Size = TII.getFrameSize(MI);
203  MaxCallFrameSize = std::max(MaxCallFrameSize, Size);
204  AdjustsStack = true;
205  } else if (MI.isInlineAsm()) {
206  // Some inline asm's need a stack frame, as indicated by operand 1.
207  unsigned ExtraInfo = MI.getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
208  if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
209  AdjustsStack = true;
210  }
211  }
212  }
213 }
214 
216  if (Objects.empty()) return;
217 
219  int ValOffset = (FI ? FI->getOffsetOfLocalArea() : 0);
220 
221  OS << "Frame Objects:\n";
222 
223  for (unsigned i = 0, e = Objects.size(); i != e; ++i) {
224  const StackObject &SO = Objects[i];
225  OS << " fi#" << (int)(i-NumFixedObjects) << ": ";
226 
227  if (SO.StackID != 0)
228  OS << "id=" << static_cast<unsigned>(SO.StackID) << ' ';
229 
230  if (SO.Size == ~0ULL) {
231  OS << "dead\n";
232  continue;
233  }
234  if (SO.Size == 0)
235  OS << "variable sized";
236  else
237  OS << "size=" << SO.Size;
238  OS << ", align=" << SO.Alignment.value();
239 
240  if (i < NumFixedObjects)
241  OS << ", fixed";
242  if (i < NumFixedObjects || SO.SPOffset != -1) {
243  int64_t Off = SO.SPOffset - ValOffset;
244  OS << ", at location [SP";
245  if (Off > 0)
246  OS << "+" << Off;
247  else if (Off < 0)
248  OS << Off;
249  OS << "]";
250  }
251  OS << "\n";
252  }
253 }
254 
255 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
257  print(MF, dbgs());
258 }
259 #endif
constexpr char Align[]
Key for Kernel::Arg::Metadata::mAlign.
bool isCalleeSavedInfoValid() const
Has the callee saved info been calculated yet?
GCNRegPressure max(const GCNRegPressure &P1, const GCNRegPressure &P2)
This class represents lattice values for constants.
Definition: AllocatorList.h:23
#define LLVM_DUMP_METHOD
Mark debug helper function definitions like dump() that should not be stripped from debug builds...
Definition: Compiler.h:473
void dump(const MachineFunction &MF) const
dump - Print the function to stderr.
virtual const TargetRegisterInfo * getRegisterInfo() const
getRegisterInfo - If register information is available, return it.
bool isDeadObjectIndex(int ObjectIdx) const
Returns true if the specified index corresponds to a dead object.
unsigned const TargetRegisterInfo * TRI
bool adjustsStack() const
Return true if this function adjusts the stack – e.g., when calling another function.
unsigned getCallFrameDestroyOpcode() const
int getOffsetOfLocalArea() const
getOffsetOfLocalArea - This method returns the offset of the local area from the stack pointer on ent...
const HexagonInstrInfo * TII
int64_t getObjectOffset(int ObjectIdx) const
Return the assigned stack offset of the specified object from the incoming stack pointer.
bool hasVarSizedObjects() const
This method may be called any time after instruction selection is complete to determine if the stack ...
Align commonAlignment(Align A, Align B)
Returns the alignment that satisfies both alignments.
Definition: Alignment.h:148
int getObjectIndexBegin() const
Return the minimum frame object index.
int getObjectIndexEnd() const
Return one past the maximum frame object index.
virtual const TargetInstrInfo * getInstrInfo() const
uint64_t value() const
This is a hole in the type system and should not be abused.
Definition: Alignment.h:75
int64_t getObjectSize(int ObjectIdx) const
Return the size of the specified object.
void ensureMaxAlignment(llvm::Align Align)
Make sure the function is at least Align bytes aligned.
uint16_t MCPhysReg
An unsigned integer type large enough to represent all physical registers, but not necessarily virtua...
Definition: MCRegister.h:19
TargetInstrInfo - Interface to description of machine instruction set.
unsigned getObjectAlignment(int ObjectIdx) const
Return the alignment of the specified stack object.
unsigned getNumRegs() const
Return the number of registers this target has (useful for sizing arrays holding per register informa...
unsigned const MachineRegisterInfo * MRI
void print(const MachineFunction &MF, raw_ostream &OS) const
Used by the MachineFunction printer to print information about stack objects.
const TargetSubtargetInfo & getSubtarget() const
getSubtarget - Return the subtarget for which this machine code is being compiled.
unsigned getCallFrameSetupOpcode() const
These methods return the opcode of the frame setup/destroy instructions if they exist (-1 otherwise)...
unsigned getMaxAlignment() const
Return the alignment in bytes that this function must be aligned to, which is greater than the defaul...
void computeMaxCallFrameSize(const MachineFunction &MF)
Computes the maximum size of a callframe and the AdjustsStack property.
TargetRegisterInfo base class - We assume that the target defines a static array of TargetRegisterDes...
MCSubRegIterator enumerates all sub-registers of Reg.
unsigned getStackAlignment() const
getStackAlignment - This method returns the number of bytes to which the stack pointer must be aligne...
virtual bool hasReservedCallFrame(const MachineFunction &MF) const
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 struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:40
int CreateStackObject(uint64_t Size, llvm::Align Alignment, bool isSpillSlot, const AllocaInst *Alloca=nullptr, uint8_t ID=0)
Create a new statically sized stack object, returning a nonnegative identifier to represent it...
int CreateSpillStackObject(uint64_t Size, llvm::Align Alignment)
Create a new statically sized stack object that represents a spill slot, returning a nonnegative iden...
unsigned getMaxCallFrameSize() const
Return the maximum size of a call frame that must be allocated for an outgoing function call...
unsigned estimateStackSize(const MachineFunction &MF) const
Estimate and return the size of the stack frame.
Information about stack frame layout on the target.
int CreateFixedSpillStackObject(uint64_t Size, int64_t SPOffset, bool IsImmutable=false)
Create a spill slot at a fixed location on the stack.
int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool IsImmutable, bool isAliased=false)
Create a new object at a fixed location on the stack.
int64_t getFrameSize(const MachineInstr &I) const
Returns size of the frame associated with the given frame instruction.
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
unsigned getTransientStackAlignment() const
getTransientStackAlignment - This method returns the number of bytes to which the stack pointer must ...
bool isValid() const
isValid - returns true if this iterator is not yet at the end.
MachineRegisterInfo - Keep track of information for virtual and physical registers, including vreg register classes, use/def chains for registers, etc.
Representation of each machine instruction.
Definition: MachineInstr.h:64
MachineRegisterInfo & getRegInfo()
getRegInfo - Return information about the registers currently in use.
const std::vector< CalleeSavedInfo > & getCalleeSavedInfo() const
Returns a reference to call saved info vector for the current function.
#define I(x, y, z)
Definition: MD5.cpp:58
virtual const TargetFrameLowering * getFrameLowering() const
uint32_t Size
Definition: Profile.cpp:46
uint8_t getStackID(int ObjectIdx) const
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
static llvm::Align clampStackAlignment(bool ShouldClamp, llvm::Align Align, llvm::Align StackAlign)
Clamp the alignment if requested and emit a warning.
bool needsStackRealignment(const MachineFunction &MF) const
True if storage within the function requires the stack pointer to be aligned more than the normal cal...
const MCPhysReg * getCalleeSavedRegs() const
Returns list of callee saved registers.
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45
IRTranslator LLVM IR MI
BitVector getPristineRegs(const MachineFunction &MF) const
Return a set of physical registers that are pristine.
int CreateVariableSizedObject(llvm::Align Alignment, const AllocaInst *Alloca)
Notify the MachineFrameInfo object that a variable sized object has been created. ...
#define LLVM_DEBUG(X)
Definition: Debug.h:122
an instruction to allocate memory on the stack
Definition: Instructions.h:59