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/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"
28 TargetFrameLowering::~TargetFrameLowering() {
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";
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();
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);
51 return MFI.getObjectOffset(FI) + MFI.getStackSize() -
52 getOffsetOfLocalArea() + MFI.getOffsetAdjustment();
55 bool TargetFrameLowering::needsFrameIndexResolution(
56 const MachineFunction &MF) const {
57 return MF.getFrameInfo().hasStackObjects();
60 void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF,
62 RegScavenger *RS) const {
63 const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
65 // Resize before the early returns. Some backends expect that
66 // SavedRegs.size() == TRI.getNumRegs() after this call even if there are no
68 SavedRegs.resize(TRI.getNumRegs());
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()))
75 // Get the callee saved register list...
76 const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF);
78 // Early exit if there are no callee saved registers.
79 if (!CSRegs || CSRegs[0] == 0)
82 // In Naked functions we aren't going to save any registers.
83 if (MF.getFunction()->hasFnAttribute(Attribute::Naked))
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))
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();