1 //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
12 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
18 class TargetRegisterClass;
20 class MachineDebugInfo;
21 class MachineFunction;
23 /// The CalleeSavedInfo class tracks the information need to locate where a
24 /// callee saved register in the current frame.
25 class CalleeSavedInfo {
29 const TargetRegisterClass *RegClass;
33 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
40 unsigned getReg() const { return Reg; }
41 const TargetRegisterClass *getRegClass() const { return RegClass; }
42 int getFrameIdx() const { return FrameIdx; }
43 void setFrameIdx(int FI) { FrameIdx = FI; }
46 /// The MachineFrameInfo class represents an abstract stack frame until
47 /// prolog/epilog code is inserted. This class is key to allowing stack frame
48 /// representation optimizations, such as frame pointer elimination. It also
49 /// allows more mundane (but still important) optimizations, such as reordering
50 /// of abstract objects on the stack frame.
52 /// To support this, the class assigns unique integer identifiers to stack
53 /// objects requested clients. These identifiers are negative integers for
54 /// fixed stack objects (such as arguments passed on the stack) or positive
55 /// for objects that may be reordered. Instructions which refer to stack
56 /// objects use a special MO_FrameIndex operand to represent these frame
59 /// Because this class keeps track of all references to the stack frame, it
60 /// knows when a variable sized object is allocated on the stack. This is the
61 /// sole condition which prevents frame pointer elimination, which is an
62 /// important optimization on register-poor architectures. Because original
63 /// variable sized alloca's in the source program are the only source of
64 /// variable sized stack objects, it is safe to decide whether there will be
65 /// any variable sized objects before all stack objects are known (for
66 /// example, register allocator spill code never needs variable sized
69 /// When prolog/epilog code emission is performed, the final stack frame is
70 /// built and the machine instructions are modified to refer to the actual
71 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
74 /// @brief Abstract Stack Frame Information
75 class MachineFrameInfo {
77 // StackObject - Represent a single object allocated on the stack.
79 // The size of this object on the stack. 0 means a variable sized object
82 // Alignment - The required alignment of this stack slot.
85 // SPOffset - The offset of this object from the stack pointer on entry to
86 // the function. This field has no meaning for a variable sized element.
89 StackObject(unsigned Sz, unsigned Al, int SP)
90 : Size(Sz), Alignment(Al), SPOffset(SP) {}
93 /// Objects - The list of stack objects allocated...
95 std::vector<StackObject> Objects;
97 /// NumFixedObjects - This contains the number of fixed objects contained on
98 /// the stack. Because fixed objects are stored at a negative index in the
99 /// Objects list, this is also the index to the 0th object in the list.
101 unsigned NumFixedObjects;
103 /// HasVarSizedObjects - This boolean keeps track of whether any variable
104 /// sized objects have been allocated yet.
106 bool HasVarSizedObjects;
108 /// StackSize - The prolog/epilog code inserter calculates the final stack
109 /// offsets for all of the fixed size objects, updating the Objects list
110 /// above. It then updates StackSize to contain the number of bytes that need
111 /// to be allocated on entry to the function.
115 /// MaxAlignment - The prolog/epilog code inserter may process objects
116 /// that require greater alignment than the default alignment the target
117 /// provides. To handle this, MaxAlignment is set to the maximum alignment
118 /// needed by the objects on the current frame. If this is greater than the
119 /// native alignment maintained by the compiler, dynamic alignment code will
122 unsigned MaxAlignment;
124 /// HasCalls - Set to true if this function has any function calls. This is
125 /// only valid during and after prolog/epilog code insertion.
128 /// MaxCallFrameSize - This contains the size of the largest call frame if the
129 /// target uses frame setup/destroy pseudo instructions (as defined in the
130 /// TargetFrameInfo class). This information is important for frame pointer
131 /// elimination. If is only valid during and after prolog/epilog code
134 unsigned MaxCallFrameSize;
136 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
137 /// callee saved register saved in the frame. Beyond it's use by the prolog/
138 /// epilog code inserter, this data used for debug info and exception
140 std::vector<CalleeSavedInfo> CSInfo;
142 /// DebugInfo - This field is set (via setMachineDebugInfo) by a debug info
143 /// consumer (ex. DwarfWriter) to indicate that frame layout information
144 /// should be acquired. Typically, it's the responsibility of the target's
145 /// MRegisterInfo prologue/epilogue emitting code to inform MachineDebugInfo
146 /// of frame layouts.
147 MachineDebugInfo *DebugInfo;
151 NumFixedObjects = StackSize = MaxAlignment = 0;
152 HasVarSizedObjects = false;
154 MaxCallFrameSize = 0;
158 /// hasStackObjects - Return true if there are any stack objects in this
161 bool hasStackObjects() const { return !Objects.empty(); }
163 /// hasVarSizedObjects - This method may be called any time after instruction
164 /// selection is complete to determine if the stack frame for this function
165 /// contains any variable sized objects.
167 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
169 /// getObjectIndexBegin - Return the minimum frame object index...
171 int getObjectIndexBegin() const { return -NumFixedObjects; }
173 /// getObjectIndexEnd - Return one past the maximum frame object index...
175 int getObjectIndexEnd() const { return Objects.size()-NumFixedObjects; }
177 /// getObjectSize - Return the size of the specified object
179 int getObjectSize(int ObjectIdx) const {
180 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
181 return Objects[ObjectIdx+NumFixedObjects].Size;
184 /// getObjectAlignment - Return the alignment of the specified stack object...
185 int getObjectAlignment(int ObjectIdx) const {
186 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
187 return Objects[ObjectIdx+NumFixedObjects].Alignment;
190 /// getObjectOffset - Return the assigned stack offset of the specified object
191 /// from the incoming stack pointer.
193 int getObjectOffset(int ObjectIdx) const {
194 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
195 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
198 /// setObjectOffset - Set the stack frame offset of the specified object. The
199 /// offset is relative to the stack pointer on entry to the function.
201 void setObjectOffset(int ObjectIdx, int SPOffset) {
202 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
203 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
206 /// getStackSize - Return the number of bytes that must be allocated to hold
207 /// all of the fixed size frame objects. This is only valid after
208 /// Prolog/Epilog code insertion has finalized the stack frame layout.
210 unsigned getStackSize() const { return StackSize; }
212 /// setStackSize - Set the size of the stack...
214 void setStackSize(unsigned Size) { StackSize = Size; }
216 /// getMaxAlignment - Return the alignment in bytes that this function must be
217 /// aligned to, which is greater than the default stack alignment provided by
220 unsigned getMaxAlignment() const { return MaxAlignment; }
222 /// setMaxAlignment - Set the preferred alignment.
224 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
226 /// hasCalls - Return true if the current function has no function calls.
227 /// This is only valid during or after prolog/epilog code emission.
229 bool hasCalls() const { return HasCalls; }
230 void setHasCalls(bool V) { HasCalls = V; }
232 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
233 /// allocated for an outgoing function call. This is only available if
234 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
235 /// then only during or after prolog/epilog code insertion.
237 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
238 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
240 /// CreateFixedObject - Create a new object at a fixed location on the stack.
241 /// All fixed objects should be created before other objects are created for
242 /// efficiency. This returns an index with a negative value.
244 int CreateFixedObject(unsigned Size, int SPOffset) {
245 assert(Size != 0 && "Cannot allocate zero size fixed stack objects!");
246 Objects.insert(Objects.begin(), StackObject(Size, 1, SPOffset));
247 return -++NumFixedObjects;
250 /// CreateStackObject - Create a new statically sized stack object, returning
251 /// a postive identifier to represent it.
253 int CreateStackObject(unsigned Size, unsigned Alignment) {
254 // Keep track of the maximum alignment.
255 if (MaxAlignment < Alignment) MaxAlignment = Alignment;
257 assert(Size != 0 && "Cannot allocate zero size stack objects!");
258 Objects.push_back(StackObject(Size, Alignment, -1));
259 return Objects.size()-NumFixedObjects-1;
262 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
263 /// variable sized object has been created. This must be created whenever a
264 /// variable sized object is created, whether or not the index returned is
267 int CreateVariableSizedObject() {
268 HasVarSizedObjects = true;
269 if (MaxAlignment < 1) MaxAlignment = 1;
270 Objects.push_back(StackObject(0, 1, -1));
271 return Objects.size()-NumFixedObjects-1;
274 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
275 /// current function.
276 std::vector<CalleeSavedInfo> &getCalleeSavedInfo() { return CSInfo; }
278 /// getMachineDebugInfo - Used by a prologue/epilogue emitter (MRegisterInfo)
279 /// to provide frame layout information.
280 MachineDebugInfo *getMachineDebugInfo() const { return DebugInfo; }
282 /// setMachineDebugInfo - Used by a debug consumer (DwarfWriter) to indicate
283 /// that frame layout information should be gathered.
284 void setMachineDebugInfo(MachineDebugInfo *DI) { DebugInfo = DI; }
286 /// print - Used by the MachineFunction printer to print information about
287 /// stack objects. Implemented in MachineFunction.cpp
289 void print(const MachineFunction &MF, std::ostream &OS) const;
291 /// dump - Call print(MF, std::cerr) to be called from the debugger.
292 void dump(const MachineFunction &MF) const;
295 } // End llvm namespace