X86AsmPrinter.h revision 280031 
1//===-- X86AsmPrinter.h - X86 implementation of AsmPrinter ------*- C++ -*-===//
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#ifndef LLVM_LIB_TARGET_X86_X86ASMPRINTER_H
11#define LLVM_LIB_TARGET_X86_X86ASMPRINTER_H
12
13#include "X86Subtarget.h"
14#include "llvm/CodeGen/AsmPrinter.h"
15#include "llvm/CodeGen/StackMaps.h"
16#include "llvm/Target/TargetMachine.h"
17
18// Implemented in X86MCInstLower.cpp
19namespace {
20  class X86MCInstLower;
21}
22
23namespace llvm {
24class MCStreamer;
25class MCSymbol;
26
27class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
28  const X86Subtarget *Subtarget;
29  StackMaps SM;
30
31  void GenerateExportDirective(const MCSymbol *Sym, bool IsData);
32
33  // This utility class tracks the length of a stackmap instruction's 'shadow'.
34  // It is used by the X86AsmPrinter to ensure that the stackmap shadow
35  // invariants (i.e. no other stackmaps, patchpoints, or control flow within
36  // the shadow) are met, while outputting a minimal number of NOPs for padding.
37  //
38  // To minimise the number of NOPs used, the shadow tracker counts the number
39  // of instruction bytes output since the last stackmap. Only if there are too
40  // few instruction bytes to cover the shadow are NOPs used for padding.
41  class StackMapShadowTracker {
42  public:
43    StackMapShadowTracker(TargetMachine &TM);
44    ~StackMapShadowTracker();
45    void startFunction(MachineFunction &MF);
46    void count(MCInst &Inst, const MCSubtargetInfo &STI);
47
48    // Called to signal the start of a shadow of RequiredSize bytes.
49    void reset(unsigned RequiredSize) {
50      RequiredShadowSize = RequiredSize;
51      CurrentShadowSize = 0;
52      InShadow = true;
53    }
54
55    // Called before every stackmap/patchpoint, and at the end of basic blocks,
56    // to emit any necessary padding-NOPs.
57    void emitShadowPadding(MCStreamer &OutStreamer, const MCSubtargetInfo &STI);
58  private:
59    TargetMachine &TM;
60    std::unique_ptr<MCCodeEmitter> CodeEmitter;
61    bool InShadow;
62
63    // RequiredShadowSize holds the length of the shadow specified in the most
64    // recently encountered STACKMAP instruction.
65    // CurrentShadowSize counts the number of bytes encoded since the most
66    // recently encountered STACKMAP, stopping when that number is greater than
67    // or equal to RequiredShadowSize.
68    unsigned RequiredShadowSize, CurrentShadowSize;
69  };
70
71  StackMapShadowTracker SMShadowTracker;
72
73  // All instructions emitted by the X86AsmPrinter should use this helper
74  // method.
75  //
76  // This helper function invokes the SMShadowTracker on each instruction before
77  // outputting it to the OutStream. This allows the shadow tracker to minimise
78  // the number of NOPs used for stackmap padding.
79  void EmitAndCountInstruction(MCInst &Inst);
80
81  void InsertStackMapShadows(MachineFunction &MF);
82  void LowerSTACKMAP(const MachineInstr &MI);
83  void LowerPATCHPOINT(const MachineInstr &MI);
84
85  void LowerTlsAddr(X86MCInstLower &MCInstLowering, const MachineInstr &MI);
86
87 public:
88  explicit X86AsmPrinter(TargetMachine &TM, MCStreamer &Streamer)
89    : AsmPrinter(TM, Streamer), SM(*this), SMShadowTracker(TM) {
90    Subtarget = &TM.getSubtarget<X86Subtarget>();
91  }
92
93  const char *getPassName() const override {
94    return "X86 Assembly / Object Emitter";
95  }
96
97  const X86Subtarget &getSubtarget() const { return *Subtarget; }
98
99  void EmitStartOfAsmFile(Module &M) override;
100
101  void EmitEndOfAsmFile(Module &M) override;
102
103  void EmitInstruction(const MachineInstr *MI) override;
104
105  void EmitBasicBlockEnd(const MachineBasicBlock &MBB) override {
106    SMShadowTracker.emitShadowPadding(OutStreamer, getSubtargetInfo());
107  }
108
109  bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
110                       unsigned AsmVariant, const char *ExtraCode,
111                       raw_ostream &OS) override;
112  bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
113                             unsigned AsmVariant, const char *ExtraCode,
114                             raw_ostream &OS) override;
115
116  /// \brief Return the symbol for the specified constant pool entry.
117  MCSymbol *GetCPISymbol(unsigned CPID) const override;
118
119  bool doInitialization(Module &M) override {
120    SMShadowTracker.reset(0);
121    SM.reset();
122    return AsmPrinter::doInitialization(M);
123  }
124
125  bool runOnMachineFunction(MachineFunction &F) override;
126};
127
128} // end namespace llvm
129
130#endif
131