Line data Source code
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/MachineRegisterInfo.h"
18 : #include "llvm/CodeGen/TargetFrameLowering.h"
19 : #include "llvm/CodeGen/TargetRegisterInfo.h"
20 : #include "llvm/CodeGen/TargetSubtargetInfo.h"
21 : #include "llvm/IR/Attributes.h"
22 : #include "llvm/IR/CallingConv.h"
23 : #include "llvm/IR/Function.h"
24 : #include "llvm/MC/MCRegisterInfo.h"
25 : #include "llvm/Support/Compiler.h"
26 : #include "llvm/Target/TargetMachine.h"
27 : #include "llvm/Target/TargetOptions.h"
28 :
29 : using namespace llvm;
30 :
31 : TargetFrameLowering::~TargetFrameLowering() = default;
32 :
33 : /// The default implementation just looks at attribute "no-frame-pointer-elim".
34 38463488 : bool TargetFrameLowering::noFramePointerElim(const MachineFunction &MF) const {
35 38463488 : auto Attr = MF.getFunction().getFnAttribute("no-frame-pointer-elim");
36 38463488 : return Attr.getValueAsString() == "true";
37 : }
38 :
39 2786 : bool TargetFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const {
40 : assert(MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
41 : MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
42 : !MF.getFunction().hasFnAttribute(Attribute::UWTable));
43 2786 : return false;
44 : }
45 :
46 : /// Returns the displacement from the frame register to the stack
47 : /// frame of the specified index, along with the frame register used
48 : /// (in output arg FrameReg). This is the default implementation which
49 : /// is overridden for some targets.
50 3426 : int TargetFrameLowering::getFrameIndexReference(const MachineFunction &MF,
51 : int FI, unsigned &FrameReg) const {
52 3426 : const MachineFrameInfo &MFI = MF.getFrameInfo();
53 3426 : const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();
54 :
55 : // By default, assume all frame indices are referenced via whatever
56 : // getFrameRegister() says. The target can override this if it's doing
57 : // something different.
58 3426 : FrameReg = RI->getFrameRegister(MF);
59 :
60 6852 : return MFI.getObjectOffset(FI) + MFI.getStackSize() -
61 6852 : getOffsetOfLocalArea() + MFI.getOffsetAdjustment();
62 : }
63 :
64 90541 : bool TargetFrameLowering::needsFrameIndexResolution(
65 : const MachineFunction &MF) const {
66 181082 : return MF.getFrameInfo().hasStackObjects();
67 : }
68 :
69 432294 : void TargetFrameLowering::determineCalleeSaves(MachineFunction &MF,
70 : BitVector &SavedRegs,
71 : RegScavenger *RS) const {
72 432294 : const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
73 :
74 : // Resize before the early returns. Some backends expect that
75 : // SavedRegs.size() == TRI.getNumRegs() after this call even if there are no
76 : // saved registers.
77 432294 : SavedRegs.resize(TRI.getNumRegs());
78 :
79 : // When interprocedural register allocation is enabled caller saved registers
80 : // are preferred over callee saved registers.
81 432294 : if (MF.getTarget().Options.EnableIPRA && isSafeForNoCSROpt(MF.getFunction()))
82 : return;
83 :
84 : // Get the callee saved register list...
85 432292 : const MCPhysReg *CSRegs = MF.getRegInfo().getCalleeSavedRegs();
86 :
87 : // Early exit if there are no callee saved registers.
88 432292 : if (!CSRegs || CSRegs[0] == 0)
89 : return;
90 :
91 : // In Naked functions we aren't going to save any registers.
92 393354 : if (MF.getFunction().hasFnAttribute(Attribute::Naked))
93 : return;
94 :
95 : // Noreturn+nounwind functions never restore CSR, so no saves are needed.
96 : // Purely noreturn functions may still return through throws, so those must
97 : // save CSR for caller exception handlers.
98 : //
99 : // If the function uses longjmp to break out of its current path of
100 : // execution we do not need the CSR spills either: setjmp stores all CSRs
101 : // it was called with into the jmp_buf, which longjmp then restores.
102 396275 : if (MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
103 5828 : MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
104 398895 : !MF.getFunction().hasFnAttribute(Attribute::UWTable) &&
105 2800 : enableCalleeSaveSkip(MF))
106 : return;
107 :
108 : // Functions which call __builtin_unwind_init get all their registers saved.
109 393257 : bool CallsUnwindInit = MF.callsUnwindInit();
110 393257 : const MachineRegisterInfo &MRI = MF.getRegInfo();
111 4744318 : for (unsigned i = 0; CSRegs[i]; ++i) {
112 4351061 : unsigned Reg = CSRegs[i];
113 4351061 : if (CallsUnwindInit || MRI.isPhysRegModified(Reg))
114 : SavedRegs.set(Reg);
115 : }
116 : }
117 :
118 404392 : unsigned TargetFrameLowering::getStackAlignmentSkew(
119 : const MachineFunction &MF) const {
120 : // When HHVM function is called, the stack is skewed as the return address
121 : // is removed from the stack before we enter the function.
122 808784 : if (LLVM_UNLIKELY(MF.getFunction().getCallingConv() == CallingConv::HHVM))
123 11 : return MF.getTarget().getAllocaPointerSize();
124 :
125 : return 0;
126 : }
127 :
128 0 : int TargetFrameLowering::getInitialCFAOffset(const MachineFunction &MF) const {
129 0 : llvm_unreachable("getInitialCFAOffset() not implemented!");
130 : }
131 :
132 0 : unsigned TargetFrameLowering::getInitialCFARegister(const MachineFunction &MF)
133 : const {
134 0 : llvm_unreachable("getInitialCFARegister() not implemented!");
135 : }
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