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/FaultMaps.h"
16 #include "llvm/CodeGen/StackMaps.h"
17 #include "llvm/Target/TargetMachine.h"
18 
19 // Implemented in X86MCInstLower.cpp
20 namespace {
21   class X86MCInstLower;
22 }
23 
24 namespace llvm {
25 class MCStreamer;
26 class MCSymbol;
27 
28 class LLVM_LIBRARY_VISIBILITY X86AsmPrinter : public AsmPrinter {
29   const X86Subtarget *Subtarget;
30   StackMaps SM;
31   FaultMaps FM;
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.
reset(unsigned RequiredSize)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     const MachineFunction *MF;
61     std::unique_ptr<MCCodeEmitter> CodeEmitter;
62     bool InShadow;
63 
64     // RequiredShadowSize holds the length of the shadow specified in the most
65     // recently encountered STACKMAP instruction.
66     // CurrentShadowSize counts the number of bytes encoded since the most
67     // recently encountered STACKMAP, stopping when that number is greater than
68     // or equal to RequiredShadowSize.
69     unsigned RequiredShadowSize, CurrentShadowSize;
70   };
71 
72   StackMapShadowTracker SMShadowTracker;
73 
74   // All instructions emitted by the X86AsmPrinter should use this helper
75   // method.
76   //
77   // This helper function invokes the SMShadowTracker on each instruction before
78   // outputting it to the OutStream. This allows the shadow tracker to minimise
79   // the number of NOPs used for stackmap padding.
80   void EmitAndCountInstruction(MCInst &Inst);
81   void LowerSTACKMAP(const MachineInstr &MI);
82   void LowerPATCHPOINT(const MachineInstr &MI, X86MCInstLower &MCIL);
83   void LowerSTATEPOINT(const MachineInstr &MI, X86MCInstLower &MCIL);
84   void LowerFAULTING_LOAD_OP(const MachineInstr &MI, X86MCInstLower &MCIL);
85 
86   void LowerTlsAddr(X86MCInstLower &MCInstLowering, const MachineInstr &MI);
87 
88  public:
X86AsmPrinter(TargetMachine & TM,std::unique_ptr<MCStreamer> Streamer)89    explicit X86AsmPrinter(TargetMachine &TM,
90                           std::unique_ptr<MCStreamer> Streamer)
91        : AsmPrinter(TM, std::move(Streamer)), SM(*this), FM(*this),
92          SMShadowTracker(TM) {}
93 
getPassName()94   const char *getPassName() const override {
95     return "X86 Assembly / Object Emitter";
96   }
97 
getSubtarget()98   const X86Subtarget &getSubtarget() const { return *Subtarget; }
99 
100   void EmitStartOfAsmFile(Module &M) override;
101 
102   void EmitEndOfAsmFile(Module &M) override;
103 
104   void EmitInstruction(const MachineInstr *MI) override;
105 
EmitBasicBlockEnd(const MachineBasicBlock & MBB)106   void EmitBasicBlockEnd(const MachineBasicBlock &MBB) override {
107     SMShadowTracker.emitShadowPadding(*OutStreamer, getSubtargetInfo());
108   }
109 
110   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
111                        unsigned AsmVariant, const char *ExtraCode,
112                        raw_ostream &OS) override;
113   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
114                              unsigned AsmVariant, const char *ExtraCode,
115                              raw_ostream &OS) override;
116 
117   /// \brief Return the symbol for the specified constant pool entry.
118   MCSymbol *GetCPISymbol(unsigned CPID) const override;
119 
doInitialization(Module & M)120   bool doInitialization(Module &M) override {
121     SMShadowTracker.reset(0);
122     SM.reset();
123     return AsmPrinter::doInitialization(M);
124   }
125 
126   bool runOnMachineFunction(MachineFunction &F) override;
127 };
128 
129 } // end namespace llvm
130 
131 #endif
132