1 //===----- TargetFrameLoweringImpl.cpp - Implement target frame interface --==//
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 // Implements the layout of a stack frame on the target machine.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/ADT/BitVector.h"
15 #include "llvm/Target/TargetFrameLowering.h"
16 #include "llvm/CodeGen/MachineFrameInfo.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/CodeGen/MachineModuleInfo.h"
19 #include "llvm/CodeGen/MachineRegisterInfo.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/Target/TargetRegisterInfo.h"
22 #include "llvm/Target/TargetSubtargetInfo.h"
26 TargetFrameLowering::~TargetFrameLowering() {
29 /// The default implementation just looks at attribute "no-frame-pointer-elim".
30 bool TargetFrameLowering::noFramePointerElim(const MachineFunction &MF) const {
31 auto Attr = MF.getFunction()->getFnAttribute("no-frame-pointer-elim");
32 return Attr.getValueAsString() == "true";
35 /// getFrameIndexOffset - Returns the displacement from the frame register to
36 /// the stack frame of the specified index. This is the default implementation
37 /// which is overridden for some targets.
38 int TargetFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
40 const MachineFrameInfo *MFI = MF.getFrameInfo();
41 return MFI->getObjectOffset(FI) + MFI->getStackSize() -
42 getOffsetOfLocalArea() + MFI->getOffsetAdjustment();
45 int TargetFrameLowering::getFrameIndexReference(const MachineFunction &MF,
46 int FI, unsigned &FrameReg) const {
47 const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();
49 // By default, assume all frame indices are referenced via whatever
50 // getFrameRegister() says. The target can override this if it's doing
51 // something different.
52 FrameReg = RI->getFrameRegister(MF);
53 return getFrameIndexOffset(MF, FI);
56 bool TargetFrameLowering::needsFrameIndexResolution(
57 const MachineFunction &MF) const {
58 return MF.getFrameInfo()->hasStackObjects();
61 void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF,
63 RegScavenger *RS) const {
64 // Get the callee saved register list...
65 const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
66 const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF);
68 // Early exit if there are no callee saved registers.
69 if (!CSRegs || CSRegs[0] == 0)
72 SavedRegs.resize(TRI.getNumRegs());
74 // In Naked functions we aren't going to save any registers.
75 if (MF.getFunction()->hasFnAttribute(Attribute::Naked))
78 // Functions which call __builtin_unwind_init get all their registers saved.
79 bool CallsUnwindInit = MF.getMMI().callsUnwindInit();
80 const MachineRegisterInfo &MRI = MF.getRegInfo();
81 for (unsigned i = 0; CSRegs[i]; ++i) {
82 unsigned Reg = CSRegs[i];
83 if (CallsUnwindInit || MRI.isPhysRegModified(Reg))