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" 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" 23 #include <cstdlib> 24 using namespace llvm; 25 26 TargetFrameLowering::~TargetFrameLowering() { 27 } 28 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"; 33 } 34 35 /// Returns the displacement from the frame register to the stack 36 /// frame of the specified index, along with the frame register used 37 /// (in output arg FrameReg). This is the default implementation which 38 /// is overridden for some targets. 39 int TargetFrameLowering::getFrameIndexReference(const MachineFunction &MF, 40 int FI, unsigned &FrameReg) const { 41 const MachineFrameInfo *MFI = MF.getFrameInfo(); 42 const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo(); 43 44 // By default, assume all frame indices are referenced via whatever 45 // getFrameRegister() says. The target can override this if it's doing 46 // something different. 47 FrameReg = RI->getFrameRegister(MF); 48 49 return MFI->getObjectOffset(FI) + MFI->getStackSize() - 50 getOffsetOfLocalArea() + MFI->getOffsetAdjustment(); 51 } 52 53 bool TargetFrameLowering::needsFrameIndexResolution( 54 const MachineFunction &MF) const { 55 return MF.getFrameInfo()->hasStackObjects(); 56 } 57 58 void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF, 59 BitVector &SavedRegs, 60 RegScavenger *RS) const { 61 // Get the callee saved register list... 62 const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo(); 63 const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF); 64 65 // Early exit if there are no callee saved registers. 66 if (!CSRegs || CSRegs[0] == 0) 67 return; 68 69 SavedRegs.resize(TRI.getNumRegs()); 70 71 // In Naked functions we aren't going to save any registers. 72 if (MF.getFunction()->hasFnAttribute(Attribute::Naked)) 73 return; 74 75 // Functions which call __builtin_unwind_init get all their registers saved. 76 bool CallsUnwindInit = MF.getMMI().callsUnwindInit(); 77 const MachineRegisterInfo &MRI = MF.getRegInfo(); 78 for (unsigned i = 0; CSRegs[i]; ++i) { 79 unsigned Reg = CSRegs[i]; 80 if (CallsUnwindInit || MRI.isPhysRegModified(Reg)) 81 SavedRegs.set(Reg); 82 } 83 } 84