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/CodeGen/MachineFrameInfo.h" 16 #include "llvm/CodeGen/MachineFunction.h" 17 #include "llvm/CodeGen/MachineModuleInfo.h" 18 #include "llvm/CodeGen/MachineRegisterInfo.h" 19 #include "llvm/CodeGen/TargetPassConfig.h" 20 #include "llvm/IR/CallingConv.h" 21 #include "llvm/IR/Function.h" 22 #include "llvm/Target/TargetFrameLowering.h" 23 #include "llvm/Target/TargetRegisterInfo.h" 24 #include "llvm/Target/TargetSubtargetInfo.h" 25 #include <cstdlib> 26 using namespace llvm; 27 28 TargetFrameLowering::~TargetFrameLowering() { 29 } 30 31 /// The default implementation just looks at attribute "no-frame-pointer-elim". 32 bool TargetFrameLowering::noFramePointerElim(const MachineFunction &MF) const { 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. 41 int TargetFrameLowering::getFrameIndexReference(const MachineFunction &MF, 42 int FI, unsigned &FrameReg) const { 43 const MachineFrameInfo *MFI = MF.getFrameInfo(); 44 const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo(); 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() - 52 getOffsetOfLocalArea() + MFI->getOffsetAdjustment(); 53 } 54 55 bool TargetFrameLowering::needsFrameIndexResolution( 56 const MachineFunction &MF) const { 57 return MF.getFrameInfo()->hasStackObjects(); 58 } 59 60 void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF, 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. 72 if (MF.getTarget().Options.EnableIPRA && isSafeForNoCSROpt(MF.getFunction())) 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.getMMI().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 96 unsigned TargetFrameLowering::getStackAlignmentSkew( 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. 100 if (LLVM_UNLIKELY(MF.getFunction()->getCallingConv() == CallingConv::HHVM)) 101 return MF.getTarget().getPointerSize(); 102 103 return 0; 104 } 105
