LLVM  4.0.0
TargetFrameLoweringImpl.cpp
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1 //===----- TargetFrameLoweringImpl.cpp - Implement target frame interface --==//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Implements the layout of a stack frame on the target machine.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ADT/BitVector.h"
20 #include "llvm/IR/CallingConv.h"
21 #include "llvm/IR/Function.h"
25 #include <cstdlib>
26 using namespace llvm;
27 
29 }
30 
31 /// The default implementation just looks at attribute "no-frame-pointer-elim".
33  auto Attr = MF.getFunction()->getFnAttribute("no-frame-pointer-elim");
34  return Attr.getValueAsString() == "true";
35 }
36 
37 /// Returns the displacement from the frame register to the stack
38 /// frame of the specified index, along with the frame register used
39 /// (in output arg FrameReg). This is the default implementation which
40 /// is overridden for some targets.
42  int FI, unsigned &FrameReg) const {
43  const MachineFrameInfo &MFI = MF.getFrameInfo();
45 
46  // By default, assume all frame indices are referenced via whatever
47  // getFrameRegister() says. The target can override this if it's doing
48  // something different.
49  FrameReg = RI->getFrameRegister(MF);
50 
51  return MFI.getObjectOffset(FI) + MFI.getStackSize() -
53 }
54 
56  const MachineFunction &MF) const {
57  return MF.getFrameInfo().hasStackObjects();
58 }
59 
61  BitVector &SavedRegs,
62  RegScavenger *RS) const {
63  const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
64 
65  // Resize before the early returns. Some backends expect that
66  // SavedRegs.size() == TRI.getNumRegs() after this call even if there are no
67  // saved registers.
68  SavedRegs.resize(TRI.getNumRegs());
69 
70  // When interprocedural register allocation is enabled caller saved registers
71  // are preferred over callee saved registers.
73  return;
74 
75  // Get the callee saved register list...
76  const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF);
77 
78  // Early exit if there are no callee saved registers.
79  if (!CSRegs || CSRegs[0] == 0)
80  return;
81 
82  // In Naked functions we aren't going to save any registers.
83  if (MF.getFunction()->hasFnAttribute(Attribute::Naked))
84  return;
85 
86  // Functions which call __builtin_unwind_init get all their registers saved.
87  bool CallsUnwindInit = MF.callsUnwindInit();
88  const MachineRegisterInfo &MRI = MF.getRegInfo();
89  for (unsigned i = 0; CSRegs[i]; ++i) {
90  unsigned Reg = CSRegs[i];
91  if (CallsUnwindInit || MRI.isPhysRegModified(Reg))
92  SavedRegs.set(Reg);
93  }
94 }
95 
97  const MachineFunction &MF) const {
98  // When HHVM function is called, the stack is skewed as the return address
99  // is removed from the stack before we enter the function.
101  return MF.getTarget().getPointerSize();
102 
103  return 0;
104 }
void resize(unsigned N, bool t=false)
resize - Grow or shrink the bitvector.
Definition: BitVector.h:193
BitVector & set()
Definition: BitVector.h:219
size_t i
#define LLVM_UNLIKELY(EXPR)
Definition: Compiler.h:182
Calling convention used by HipHop Virtual Machine (HHVM) to perform calls to and from translation cac...
Definition: CallingConv.h:159
virtual unsigned getStackAlignmentSkew(const MachineFunction &MF) const
Return the skew that has to be applied to stack alignment under certain conditions (e...
uint16_t MCPhysReg
An unsigned integer type large enough to represent all physical registers, but not necessarily virtua...
Attribute getFnAttribute(Attribute::AttrKind Kind) const
Return the attribute for the given attribute kind.
Definition: Function.h:234
const Function * getFunction() const
getFunction - Return the LLVM function that this machine code represents
CallingConv::ID getCallingConv() const
getCallingConv()/setCallingConv(CC) - These method get and set the calling convention of this functio...
Definition: Function.h:165
uint64_t getStackSize() const
Return the number of bytes that must be allocated to hold all of the fixed size frame objects...
const TargetSubtargetInfo & getSubtarget() const
getSubtarget - Return the subtarget for which this machine code is being compiled.
unsigned EnableIPRA
This flag enables InterProcedural Register Allocation (IPRA).
Reg
All possible values of the reg field in the ModR/M byte.
The MachineFrameInfo class represents an abstract stack frame until prolog/epilog code is inserted...
virtual unsigned getFrameRegister(const MachineFunction &MF) const =0
Debug information queries.
unsigned getNumRegs() const
Return the number of registers this target has (useful for sizing arrays holding per register informa...
bool hasStackObjects() const
Return true if there are any stack objects in this function.
int getOffsetAdjustment() const
Return the correction for frame offsets.
virtual bool needsFrameIndexResolution(const MachineFunction &MF) const
virtual const MCPhysReg * getCalleeSavedRegs(const MachineFunction *MF) const =0
Return a null-terminated list of all of the callee-saved registers on this target.
virtual int getFrameIndexReference(const MachineFunction &MF, int FI, unsigned &FrameReg) const
getFrameIndexReference - This method should return the base register and offset used to reference a f...
unsigned const MachineRegisterInfo * MRI
MachineFrameInfo & getFrameInfo()
getFrameInfo - Return the frame info object for the current function.
TargetRegisterInfo base class - We assume that the target defines a static array of TargetRegisterDes...
int64_t getObjectOffset(int ObjectIdx) const
Return the assigned stack offset of the specified object from the incoming stack pointer.
virtual void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs, RegScavenger *RS=nullptr) const
This method determines which of the registers reported by TargetRegisterInfo::getCalleeSavedRegs() sh...
virtual bool noFramePointerElim(const MachineFunction &MF) const
Return true if the target needs to disable frame pointer elimination.
int getOffsetOfLocalArea() const
getOffsetOfLocalArea - This method returns the offset of the local area from the stack pointer on ent...
MachineRegisterInfo - Keep track of information for virtual and physical registers, including vreg register classes, use/def chains for registers, etc.
static bool isSafeForNoCSROpt(const Function *F)
Check if given function is safe for not having callee saved registers.
bool hasFnAttribute(Attribute::AttrKind Kind) const
Return true if the function has the attribute.
Definition: Function.h:226
MachineRegisterInfo & getRegInfo()
getRegInfo - Return information about the registers currently in use.
bool callsUnwindInit() const
const TargetMachine & getTarget() const
getTarget - Return the target machine this machine code is compiled with
bool isPhysRegModified(unsigned PhysReg, bool SkipNoReturnDef=false) const
Return true if the specified register is modified in this function.
unsigned getPointerSize() const
Get the pointer size for this target.
StringRef getValueAsString() const
Return the attribute's value as a string.
Definition: Attributes.cpp:178
virtual const TargetRegisterInfo * getRegisterInfo() const
getRegisterInfo - If register information is available, return it.