LCOV - code coverage report
Current view: top level - include/llvm/MC - MCAsmBackend.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 8 10 80.0 %
Date: 2017-09-14 15:23:50 Functions: 7 9 77.8 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- llvm/MC/MCAsmBackend.h - MC Asm Backend ------------------*- 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_MC_MCASMBACKEND_H
      11             : #define LLVM_MC_MCASMBACKEND_H
      12             : 
      13             : #include "llvm/ADT/ArrayRef.h"
      14             : #include "llvm/ADT/Optional.h"
      15             : #include "llvm/ADT/StringRef.h"
      16             : #include "llvm/MC/MCDirectives.h"
      17             : #include "llvm/MC/MCFixup.h"
      18             : #include <cstdint>
      19             : 
      20             : namespace llvm {
      21             : 
      22             : class MCAsmLayout;
      23             : class MCAssembler;
      24             : class MCCFIInstruction;
      25             : struct MCFixupKindInfo;
      26             : class MCFragment;
      27             : class MCInst;
      28             : class MCObjectWriter;
      29             : class MCRelaxableFragment;
      30             : class MCSubtargetInfo;
      31             : class MCValue;
      32             : class raw_pwrite_stream;
      33             : 
      34             : /// Generic interface to target specific assembler backends.
      35       40380 : class MCAsmBackend {
      36             : protected: // Can only create subclasses.
      37             :   MCAsmBackend();
      38             : 
      39             : public:
      40             :   MCAsmBackend(const MCAsmBackend &) = delete;
      41             :   MCAsmBackend &operator=(const MCAsmBackend &) = delete;
      42             :   virtual ~MCAsmBackend();
      43             : 
      44             :   /// lifetime management
      45        1582 :   virtual void reset() {}
      46             : 
      47             :   /// Create a new MCObjectWriter instance for use by the assembler backend to
      48             :   /// emit the final object file.
      49             :   virtual MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const = 0;
      50             : 
      51             :   /// \name Target Fixup Interfaces
      52             :   /// @{
      53             : 
      54             :   /// Get the number of target specific fixup kinds.
      55             :   virtual unsigned getNumFixupKinds() const = 0;
      56             : 
      57             :   /// Map a relocation name used in .reloc to a fixup kind.
      58             :   virtual Optional<MCFixupKind> getFixupKind(StringRef Name) const;
      59             : 
      60             :   /// Get information on a fixup kind.
      61             :   virtual const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const;
      62             : 
      63             :   /// Hook to check if a relocation is needed for some target specific reason.
      64      260187 :   virtual bool shouldForceRelocation(const MCAssembler &Asm,
      65             :                                      const MCFixup &Fixup,
      66             :                                      const MCValue &Target) {
      67      260187 :     return false;
      68             :   }
      69             : 
      70             :   /// Apply the \p Value for given \p Fixup into the provided data fragment, at
      71             :   /// the offset specified by the fixup and following the fixup kind as
      72             :   /// appropriate. Errors (such as an out of range fixup value) should be
      73             :   /// reported via \p Ctx.
      74             :   virtual void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
      75             :                           const MCValue &Target, MutableArrayRef<char> Data,
      76             :                           uint64_t Value, bool IsResolved) const = 0;
      77             : 
      78             :   /// @}
      79             : 
      80             :   /// \name Target Relaxation Interfaces
      81             :   /// @{
      82             : 
      83             :   /// Check whether the given instruction may need relaxation.
      84             :   ///
      85             :   /// \param Inst - The instruction to test.
      86             :   virtual bool mayNeedRelaxation(const MCInst &Inst) const = 0;
      87             : 
      88             :   /// Target specific predicate for whether a given fixup requires the
      89             :   /// associated instruction to be relaxed.
      90             :   virtual bool fixupNeedsRelaxationAdvanced(const MCFixup &Fixup, bool Resolved,
      91             :                                             uint64_t Value,
      92             :                                             const MCRelaxableFragment *DF,
      93             :                                             const MCAsmLayout &Layout) const;
      94             : 
      95             :   /// Simple predicate for targets where !Resolved implies requiring relaxation
      96             :   virtual bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
      97             :                                     const MCRelaxableFragment *DF,
      98             :                                     const MCAsmLayout &Layout) const = 0;
      99             : 
     100             :   /// Relax the instruction in the given fragment to the next wider instruction.
     101             :   ///
     102             :   /// \param Inst The instruction to relax, which may be the same as the
     103             :   /// output.
     104             :   /// \param STI the subtarget information for the associated instruction.
     105             :   /// \param [out] Res On return, the relaxed instruction.
     106             :   virtual void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
     107             :                                 MCInst &Res) const = 0;
     108             : 
     109             :   /// @}
     110             : 
     111             :   /// Returns the minimum size of a nop in bytes on this target. The assembler
     112             :   /// will use this to emit excess padding in situations where the padding
     113             :   /// required for simple alignment would be less than the minimum nop size.
     114             :   ///
     115       10311 :   virtual unsigned getMinimumNopSize() const { return 1; }
     116             : 
     117             :   /// Write an (optimal) nop sequence of Count bytes to the given output. If the
     118             :   /// target cannot generate such a sequence, it should return an error.
     119             :   ///
     120             :   /// \return - True on success.
     121             :   virtual bool writeNopData(uint64_t Count, MCObjectWriter *OW) const = 0;
     122             : 
     123             :   /// Give backend an opportunity to finish layout after relaxation
     124        3994 :   virtual void finishLayout(MCAssembler const &Asm,
     125        3994 :                             MCAsmLayout &Layout) const {}
     126             : 
     127             :   /// Handle any target-specific assembler flags. By default, do nothing.
     128         231 :   virtual void handleAssemblerFlag(MCAssemblerFlag Flag) {}
     129             : 
     130             :   /// \brief Generate the compact unwind encoding for the CFI instructions.
     131             :   virtual uint32_t
     132           0 :       generateCompactUnwindEncoding(ArrayRef<MCCFIInstruction>) const {
     133           0 :     return 0;
     134             :   }
     135             : };
     136             : 
     137             : } // end namespace llvm
     138             : 
     139             : #endif // LLVM_MC_MCASMBACKEND_H

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