LCOV - code coverage report
Current view: top level - include/llvm/MC - MCCodePadder.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 9 13 69.2 %
Date: 2018-05-20 00:06:23 Functions: 4 6 66.7 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- llvm/MC/CodePadder.h - MC Code Padder --------------------*- 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_MCCODEPADDER_H
      11             : #define LLVM_MC_MCCODEPADDER_H
      12             : 
      13             : #include "MCFragment.h"
      14             : #include "llvm/ADT/DenseMap.h"
      15             : #include "llvm/ADT/SmallPtrSet.h"
      16             : #include "llvm/ADT/SmallVector.h"
      17             : 
      18             : namespace llvm {
      19             : 
      20             : class MCAsmLayout;
      21             : class MCCodePaddingPolicy;
      22             : class MCFragment;
      23             : class MCInst;
      24             : class MCObjectStreamer;
      25             : class MCSection;
      26             : 
      27             : typedef SmallVector<const MCPaddingFragment *, 8> MCPFRange;
      28             : 
      29             : struct MCCodePaddingContext {
      30             :   bool IsPaddingActive;
      31             :   bool IsBasicBlockReachableViaFallthrough;
      32             :   bool IsBasicBlockReachableViaBranch;
      33             : };
      34             : 
      35             : /// Target-independent base class incharge of all code padding decisions for a
      36             : /// target. During encoding it determines if and where MCPaddingFragments will
      37             : /// be located, as later on, when layout information is available, it determines
      38             : /// their sizes.
      39             : class MCCodePadder {
      40             :   MCCodePadder(const MCCodePadder &) = delete;
      41             :   void operator=(const MCCodePadder &) = delete;
      42             : 
      43             :   /// Determines if the MCCodePaddingPolicies are active.
      44             :   bool ArePoliciesActive;
      45             : 
      46             :   /// All the supported MCCodePaddingPolicies.
      47             :   SmallPtrSet<MCCodePaddingPolicy *, 4> CodePaddingPolicies;
      48             : 
      49             :   /// A pointer to the fragment of the instruction whose padding is currently
      50             :   /// done for.
      51             :   MCPaddingFragment *CurrHandledInstFragment;
      52             : 
      53             :   /// A map holding the jurisdiction for each padding fragment. Key: padding
      54             :   /// fragment. Value: The fragment's jurisdiction. A jurisdiction is a vector
      55             :   /// of padding fragments whose conditions are being controlled by another
      56             :   /// fragment, the key fragment.
      57             :   DenseMap<MCPaddingFragment *, MCPFRange> FragmentToJurisdiction;
      58             :   MCPFRange &getJurisdiction(MCPaddingFragment *Fragment, MCAsmLayout &Layout);
      59             : 
      60             :   /// A map holding the maximal instruction window size relevant for a padding
      61             :   /// fragment.
      62             :   DenseMap<MCPaddingFragment *, uint64_t> FragmentToMaxWindowSize;
      63             :   uint64_t getMaxWindowSize(MCPaddingFragment *Fragment, MCAsmLayout &Layout);
      64             : 
      65             : protected:
      66             :   /// The current streamer, used to stream code padding.
      67             :   MCObjectStreamer *OS;
      68             : 
      69             :   bool addPolicy(MCCodePaddingPolicy *Policy);
      70             : 
      71             :   virtual bool
      72      217657 :   basicBlockRequiresInsertionPoint(const MCCodePaddingContext &Context) {
      73      217657 :     return false;
      74             :   }
      75             : 
      76     2021504 :   virtual bool instructionRequiresInsertionPoint(const MCInst &Inst) {
      77     2021504 :     return false;
      78             :   }
      79             : 
      80      217656 :   virtual bool usePoliciesForBasicBlock(const MCCodePaddingContext &Context) {
      81      217656 :     return Context.IsPaddingActive;
      82             :   }
      83             : 
      84             : public:
      85       27983 :   MCCodePadder()
      86       27983 :       : ArePoliciesActive(false), CurrHandledInstFragment(nullptr),
      87      111934 :         OS(nullptr) {}
      88             :   virtual ~MCCodePadder();
      89             : 
      90             :   /// Handles all target related code padding when starting to write a new
      91             :   /// basic block to an object file.
      92             :   ///
      93             :   /// \param OS The streamer used for writing the padding data and function.
      94             :   /// \param Context the context of the padding, Embeds the basic block's
      95             :   /// parameters.
      96             :   void handleBasicBlockStart(MCObjectStreamer *OS,
      97             :                              const MCCodePaddingContext &Context);
      98             :   /// Handles all target related code padding when done writing a block to an
      99             :   /// object file.
     100             :   ///
     101             :   /// \param Context the context of the padding, Embeds the basic block's
     102             :   /// parameters.
     103             :   void handleBasicBlockEnd(const MCCodePaddingContext &Context);
     104             :   /// Handles all target related code padding before writing a new instruction
     105             :   /// to an object file.
     106             :   ///
     107             :   /// \param Inst the instruction.
     108             :   void handleInstructionBegin(const MCInst &Inst);
     109             :   /// Handles all target related code padding after writing an instruction to an
     110             :   /// object file.
     111             :   ///
     112             :   /// \param Inst the instruction.
     113             :   void handleInstructionEnd(const MCInst &Inst);
     114             : 
     115             :   /// Relaxes a fragment (changes the size of the padding) according to target
     116             :   /// requirements. The new size computation is done w.r.t a layout.
     117             :   ///
     118             :   /// \param Fragment The fragment to relax.
     119             :   /// \param Layout Code layout information.
     120             :   ///
     121             :   /// \returns true iff any relaxation occurred.
     122             :   bool relaxFragment(MCPaddingFragment *Fragment, MCAsmLayout &Layout);
     123             : };
     124             : 
     125             : /// The base class for all padding policies, i.e. a rule or set of rules to pad
     126             : /// the generated code.
     127             : class MCCodePaddingPolicy {
     128             :   MCCodePaddingPolicy() = delete;
     129             :   MCCodePaddingPolicy(const MCCodePaddingPolicy &) = delete;
     130             :   void operator=(const MCCodePaddingPolicy &) = delete;
     131             : 
     132             : protected:
     133             :   /// A mask holding the kind of this policy, i.e. only the i'th bit will be set
     134             :   /// where i is the kind number.
     135             :   const uint64_t KindMask;
     136             :   /// Instruction window size relevant to this policy.
     137             :   const uint64_t WindowSize;
     138             :   /// A boolean indicating which byte of the instruction determies its
     139             :   /// instruction window. If true - the last byte of the instructions, o.w. -
     140             :   /// the first byte of the instruction.
     141             :   const bool InstByteIsLastByte;
     142             : 
     143             :   MCCodePaddingPolicy(uint64_t Kind, uint64_t WindowSize,
     144             :                       bool InstByteIsLastByte)
     145             :       : KindMask(UINT64_C(1) << Kind), WindowSize(WindowSize),
     146             :         InstByteIsLastByte(InstByteIsLastByte) {}
     147             : 
     148             :   /// Computes and returns the offset of the consecutive fragment of a given
     149             :   /// fragment.
     150             :   ///
     151             :   /// \param Fragment The fragment whose consecutive offset will be computed.
     152             :   /// \param Layout Code layout information.
     153             :   ///
     154             :   /// \returns the offset of the consecutive fragment of \p Fragment.
     155             :   static uint64_t getNextFragmentOffset(const MCFragment *Fragment,
     156             :                                         const MCAsmLayout &Layout);
     157             :   /// Returns the instruction byte of an instruction pointed by a given
     158             :   /// MCPaddingFragment. An instruction byte is the address of the byte of an
     159             :   /// instruction which determines its instruction window.
     160             :   ///
     161             :   /// \param Fragment The fragment pointing to the instruction.
     162             :   /// \param Layout Code layout information.
     163             :   ///
     164             :   /// \returns the instruction byte of an instruction pointed by \p Fragment.
     165             :   uint64_t getFragmentInstByte(const MCPaddingFragment *Fragment,
     166             :                                MCAsmLayout &Layout) const;
     167             :   uint64_t computeWindowEndAddress(const MCPaddingFragment *Fragment,
     168             :                                    uint64_t Offset, MCAsmLayout &Layout) const;
     169             : 
     170             :   /// Computes and returns the penalty weight of a first instruction window in a
     171             :   /// range. This requires a special function since the first window does not
     172             :   /// contain all the padding fragments in that window. It only contains all the
     173             :   /// padding fragments starting from the relevant insertion point.
     174             :   ///
     175             :   /// \param Window The first window.
     176             :   /// \param Offset The offset of the parent section relative to the beginning
     177             :   /// of the file, mod the window size.
     178             :   /// \param Layout Code layout information.
     179             :   ///
     180             :   /// \returns the penalty weight of a first instruction window in a range, \p
     181             :   /// Window.
     182             :   double computeFirstWindowPenaltyWeight(const MCPFRange &Window,
     183             :                                          uint64_t Offset,
     184             :                                          MCAsmLayout &Layout) const;
     185             :   /// Computes and returns the penalty caused by an instruction window.
     186             :   ///
     187             :   /// \param Window The instruction window.
     188             :   /// \param Offset The offset of the parent section relative to the beginning
     189             :   /// of the file, mod the window size.
     190             :   /// \param Layout Code layout information.
     191             :   ///
     192             :   /// \returns the penalty caused by \p Window.
     193             :   virtual double computeWindowPenaltyWeight(const MCPFRange &Window,
     194             :                                             uint64_t Offset,
     195             :                                             MCAsmLayout &Layout) const = 0;
     196             : 
     197             : public:
     198             :   virtual ~MCCodePaddingPolicy() {}
     199             : 
     200             :   /// Returns the kind mask of this policy -  A mask holding the kind of this
     201             :   /// policy, i.e. only the i'th bit will be set where i is the kind number.
     202             :   uint64_t getKindMask() const { return KindMask; }
     203             :   /// Returns the instruction window size relevant to this policy.
     204             :   uint64_t getWindowSize() const { return WindowSize; }
     205             :   /// Returns true if the last byte of an instruction determines its instruction
     206             :   /// window, or false if the first of an instruction determines it.
     207             :   bool isInstByteLastByte() const { return InstByteIsLastByte; }
     208             : 
     209             :   /// Returns true iff this policy needs padding for a given basic block.
     210             :   ///
     211             :   /// \param Context the context of the padding, Embeds the basic block's
     212             :   /// parameters.
     213             :   ///
     214             :   /// \returns true iff this policy needs padding for the basic block.
     215             :   virtual bool
     216           0 :   basicBlockRequiresPaddingFragment(const MCCodePaddingContext &Context) const {
     217           0 :     return false;
     218             :   }
     219             :   /// Returns true iff this policy needs padding for a given instruction.
     220             :   ///
     221             :   /// \param Inst The given instruction.
     222             :   ///
     223             :   /// \returns true iff this policy needs padding for \p Inst.
     224           0 :   virtual bool instructionRequiresPaddingFragment(const MCInst &Inst) const {
     225           0 :     return false;
     226             :   }
     227             :   /// Computes and returns the penalty caused by a range of instruction windows.
     228             :   /// The weight is computed for each window separelty and then accumulated.
     229             :   ///
     230             :   /// \param Range The range.
     231             :   /// \param Offset The offset of the parent section relative to the beginning
     232             :   /// of the file, mod the window size.
     233             :   /// \param Layout Code layout information.
     234             :   ///
     235             :   /// \returns the penalty caused by \p Range.
     236             :   double computeRangePenaltyWeight(const MCPFRange &Range, uint64_t Offset,
     237             :                                    MCAsmLayout &Layout) const;
     238             : };
     239             : 
     240             : } // namespace llvm
     241             : 
     242             : #endif // LLVM_MC_MCCODEPADDER_H

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