1 //===-- llvm/Target/TargetFrameLowering.h ---------------------------*- C++ -*-===//
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 //===----------------------------------------------------------------------===//
10 // Interface to describe the layout of a stack frame on the target machine.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_TARGET_TARGETFRAMELOWERING_H
15 #define LLVM_TARGET_TARGETFRAMELOWERING_H
17 #include "llvm/CodeGen/MachineBasicBlock.h"
18 #include "llvm/MC/MCDwarf.h"
19 #include "llvm/ADT/ArrayRef.h"
25 class CalleeSavedInfo;
26 class MachineFunction;
27 class MachineBasicBlock;
31 /// Information about stack frame layout on the target. It holds the direction
32 /// of stack growth, the known stack alignment on entry to each function, and
33 /// the offset to the locals area.
35 /// The offset to the local area is the offset from the stack pointer on
36 /// function entry to the first location where function data (local variables,
37 /// spill locations) can be stored.
38 class TargetFrameLowering {
41 StackGrowsUp, // Adding to the stack increases the stack address
42 StackGrowsDown // Adding to the stack decreases the stack address
45 // Maps a callee saved register to a stack slot with a fixed offset.
48 int Offset; // Offset relative to stack pointer on function entry.
51 StackDirection StackDir;
52 unsigned StackAlignment;
53 unsigned TransientStackAlignment;
56 TargetFrameLowering(StackDirection D, unsigned StackAl, int LAO,
58 : StackDir(D), StackAlignment(StackAl), TransientStackAlignment(TransAl),
59 LocalAreaOffset(LAO) {}
61 virtual ~TargetFrameLowering();
63 // These methods return information that describes the abstract stack layout
64 // of the target machine.
66 /// getStackGrowthDirection - Return the direction the stack grows
68 StackDirection getStackGrowthDirection() const { return StackDir; }
70 /// getStackAlignment - This method returns the number of bytes to which the
71 /// stack pointer must be aligned on entry to a function. Typically, this
72 /// is the largest alignment for any data object in the target.
74 unsigned getStackAlignment() const { return StackAlignment; }
76 /// getTransientStackAlignment - This method returns the number of bytes to
77 /// which the stack pointer must be aligned at all times, even between
80 unsigned getTransientStackAlignment() const {
81 return TransientStackAlignment;
84 /// getOffsetOfLocalArea - This method returns the offset of the local area
85 /// from the stack pointer on entrance to a function.
87 int getOffsetOfLocalArea() const { return LocalAreaOffset; }
89 /// getCalleeSavedSpillSlots - This method returns a pointer to an array of
90 /// pairs, that contains an entry for each callee saved register that must be
91 /// spilled to a particular stack location if it is spilled.
93 /// Each entry in this array contains a <register,offset> pair, indicating the
94 /// fixed offset from the incoming stack pointer that each register should be
95 /// spilled at. If a register is not listed here, the code generator is
96 /// allowed to spill it anywhere it chooses.
98 virtual const SpillSlot *
99 getCalleeSavedSpillSlots(unsigned &NumEntries) const {
104 /// targetHandlesStackFrameRounding - Returns true if the target is
105 /// responsible for rounding up the stack frame (probably at emitPrologue
107 virtual bool targetHandlesStackFrameRounding() const {
111 /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
113 virtual void emitPrologue(MachineFunction &MF) const = 0;
114 virtual void emitEpilogue(MachineFunction &MF,
115 MachineBasicBlock &MBB) const = 0;
117 /// Adjust the prologue to have the function use segmented stacks. This works
118 /// by adding a check even before the "normal" function prologue.
119 virtual void adjustForSegmentedStacks(MachineFunction &MF) const { }
121 /// spillCalleeSavedRegisters - Issues instruction(s) to spill all callee
122 /// saved registers and returns true if it isn't possible / profitable to do
123 /// so by issuing a series of store instructions via
124 /// storeRegToStackSlot(). Returns false otherwise.
125 virtual bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
126 MachineBasicBlock::iterator MI,
127 const std::vector<CalleeSavedInfo> &CSI,
128 const TargetRegisterInfo *TRI) const {
132 /// restoreCalleeSavedRegisters - Issues instruction(s) to restore all callee
133 /// saved registers and returns true if it isn't possible / profitable to do
134 /// so by issuing a series of load instructions via loadRegToStackSlot().
135 /// Returns false otherwise.
136 virtual bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
137 MachineBasicBlock::iterator MI,
138 const std::vector<CalleeSavedInfo> &CSI,
139 const TargetRegisterInfo *TRI) const {
143 /// hasFP - Return true if the specified function should have a dedicated
144 /// frame pointer register. For most targets this is true only if the function
145 /// has variable sized allocas or if frame pointer elimination is disabled.
146 virtual bool hasFP(const MachineFunction &MF) const = 0;
148 /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
149 /// not required, we reserve argument space for call sites in the function
150 /// immediately on entry to the current function. This eliminates the need for
151 /// add/sub sp brackets around call sites. Returns true if the call frame is
152 /// included as part of the stack frame.
153 virtual bool hasReservedCallFrame(const MachineFunction &MF) const {
157 /// canSimplifyCallFramePseudos - When possible, it's best to simplify the
158 /// call frame pseudo ops before doing frame index elimination. This is
159 /// possible only when frame index references between the pseudos won't
160 /// need adjusting for the call frame adjustments. Normally, that's true
161 /// if the function has a reserved call frame or a frame pointer. Some
162 /// targets (Thumb2, for example) may have more complicated criteria,
163 /// however, and can override this behavior.
164 virtual bool canSimplifyCallFramePseudos(const MachineFunction &MF) const {
165 return hasReservedCallFrame(MF) || hasFP(MF);
168 /// getFrameIndexOffset - Returns the displacement from the frame register to
169 /// the stack frame of the specified index.
170 virtual int getFrameIndexOffset(const MachineFunction &MF, int FI) const;
172 /// getFrameIndexReference - This method should return the base register
173 /// and offset used to reference a frame index location. The offset is
174 /// returned directly, and the base register is returned via FrameReg.
175 virtual int getFrameIndexReference(const MachineFunction &MF, int FI,
176 unsigned &FrameReg) const;
178 /// processFunctionBeforeCalleeSavedScan - This method is called immediately
179 /// before PrologEpilogInserter scans the physical registers used to determine
180 /// what callee saved registers should be spilled. This method is optional.
181 virtual void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
182 RegScavenger *RS = NULL) const {
186 /// processFunctionBeforeFrameFinalized - This method is called immediately
187 /// before the specified function's frame layout (MF.getFrameInfo()) is
188 /// finalized. Once the frame is finalized, MO_FrameIndex operands are
189 /// replaced with direct constants. This method is optional.
191 virtual void processFunctionBeforeFrameFinalized(MachineFunction &MF) const {
195 } // End llvm namespace