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: 2018-02-18 03:11:45 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 IsBasicBlockInsideInnermostLoop;
      32             :   bool IsBasicBlockReachableViaFallthrough;
      33             :   bool IsBasicBlockReachableViaBranch;
      34             : };
      35             : 
      36             : /// Target-independent base class incharge of all code padding decisions for a
      37             : /// target. During encoding it determines if and where MCPaddingFragments will
      38             : /// be located, as later on, when layout information is available, it determines
      39             : /// their sizes.
      40             : class MCCodePadder {
      41             :   MCCodePadder(const MCCodePadder &) = delete;
      42             :   void operator=(const MCCodePadder &) = delete;
      43             : 
      44             :   /// Determines if the MCCodePaddingPolicies are active.
      45             :   bool ArePoliciesActive;
      46             : 
      47             :   /// All the supported MCCodePaddingPolicies.
      48             :   SmallPtrSet<MCCodePaddingPolicy *, 4> CodePaddingPolicies;
      49             : 
      50             :   /// A pointer to the fragment of the instruction whose padding is currently
      51             :   /// done for.
      52             :   MCPaddingFragment *CurrHandledInstFragment;
      53             : 
      54             :   /// A map holding the jurisdiction for each padding fragment. Key: padding
      55             :   /// fragment. Value: The fragment's jurisdiction. A jurisdiction is a vector
      56             :   /// of padding fragments whose conditions are being controlled by another
      57             :   /// fragment, the key fragment.
      58             :   DenseMap<MCPaddingFragment *, MCPFRange> FragmentToJurisdiction;
      59             :   MCPFRange &getJurisdiction(MCPaddingFragment *Fragment, MCAsmLayout &Layout);
      60             : 
      61             :   /// A map holding the maximal instruction window size relevant for a padding
      62             :   /// fragment.
      63             :   DenseMap<MCPaddingFragment *, uint64_t> FragmentToMaxWindowSize;
      64             :   uint64_t getMaxWindowSize(MCPaddingFragment *Fragment, MCAsmLayout &Layout);
      65             : 
      66             : protected:
      67             :   /// The current streamer, used to stream code padding.
      68             :   MCObjectStreamer *OS;
      69             : 
      70             :   bool addPolicy(MCCodePaddingPolicy *Policy);
      71             : 
      72             :   virtual bool
      73      209497 :   basicBlockRequiresInsertionPoint(const MCCodePaddingContext &Context) {
      74      209497 :     return false;
      75             :   }
      76             : 
      77     2219748 :   virtual bool instructionRequiresInsertionPoint(const MCInst &Inst) {
      78     2219748 :     return false;
      79             :   }
      80             : 
      81      209497 :   virtual bool usePoliciesForBasicBlock(const MCCodePaddingContext &Context) {
      82      209497 :     return Context.IsPaddingActive;
      83             :   }
      84             : 
      85             : public:
      86       24791 :   MCCodePadder()
      87       24791 :       : ArePoliciesActive(false), CurrHandledInstFragment(nullptr),
      88       99164 :         OS(nullptr) {}
      89             :   virtual ~MCCodePadder();
      90             : 
      91             :   /// Handles all target related code padding when starting to write a new
      92             :   /// basic block to an object file.
      93             :   ///
      94             :   /// \param OS The streamer used for writing the padding data and function.
      95             :   /// \param Context the context of the padding, Embeds the basic block's
      96             :   /// parameters.
      97             :   void handleBasicBlockStart(MCObjectStreamer *OS,
      98             :                              const MCCodePaddingContext &Context);
      99             :   /// Handles all target related code padding when done writing a block to an
     100             :   /// object file.
     101             :   ///
     102             :   /// \param Context the context of the padding, Embeds the basic block's
     103             :   /// parameters.
     104             :   void handleBasicBlockEnd(const MCCodePaddingContext &Context);
     105             :   /// Handles all target related code padding before writing a new instruction
     106             :   /// to an object file.
     107             :   ///
     108             :   /// \param Inst the instruction.
     109             :   void handleInstructionBegin(const MCInst &Inst);
     110             :   /// Handles all target related code padding after writing an instruction to an
     111             :   /// object file.
     112             :   ///
     113             :   /// \param Inst the instruction.
     114             :   void handleInstructionEnd(const MCInst &Inst);
     115             : 
     116             :   /// Relaxes a fragment (changes the size of the padding) according to target
     117             :   /// requirements. The new size computation is done w.r.t a layout.
     118             :   ///
     119             :   /// \param Fragment The fragment to relax.
     120             :   /// \param Layout Code layout information.
     121             :   ///
     122             :   /// \returns true iff any relaxation occurred.
     123             :   bool relaxFragment(MCPaddingFragment *Fragment, MCAsmLayout &Layout);
     124             : };
     125             : 
     126             : /// The base class for all padding policies, i.e. a rule or set of rules to pad
     127             : /// the generated code.
     128             : class MCCodePaddingPolicy {
     129             :   MCCodePaddingPolicy() = delete;
     130             :   MCCodePaddingPolicy(const MCCodePaddingPolicy &) = delete;
     131             :   void operator=(const MCCodePaddingPolicy &) = delete;
     132             : 
     133             : protected:
     134             :   /// A mask holding the kind of this policy, i.e. only the i'th bit will be set
     135             :   /// where i is the kind number.
     136             :   const uint64_t KindMask;
     137             :   /// Instruction window size relevant to this policy.
     138             :   const uint64_t WindowSize;
     139             :   /// A boolean indicating which byte of the instruction determies its
     140             :   /// instruction window. If true - the last byte of the instructions, o.w. -
     141             :   /// the first byte of the instruction.
     142             :   const bool InstByteIsLastByte;
     143             : 
     144             :   MCCodePaddingPolicy(uint64_t Kind, uint64_t WindowSize,
     145             :                       bool InstByteIsLastByte)
     146             :       : KindMask(UINT64_C(1) << Kind), WindowSize(WindowSize),
     147             :         InstByteIsLastByte(InstByteIsLastByte) {}
     148             : 
     149             :   /// Computes and returns the offset of the consecutive fragment of a given
     150             :   /// fragment.
     151             :   ///
     152             :   /// \param Fragment The fragment whose consecutive offset will be computed.
     153             :   /// \param Layout Code layout information.
     154             :   ///
     155             :   /// \returns the offset of the consecutive fragment of \p Fragment.
     156             :   static uint64_t getNextFragmentOffset(const MCFragment *Fragment,
     157             :                                         const MCAsmLayout &Layout);
     158             :   /// Returns the instruction byte of an instruction pointed by a given
     159             :   /// MCPaddingFragment. An instruction byte is the address of the byte of an
     160             :   /// instruction which determines its instruction window.
     161             :   ///
     162             :   /// \param Fragment The fragment pointing to the instruction.
     163             :   /// \param Layout Code layout information.
     164             :   ///
     165             :   /// \returns the instruction byte of an instruction pointed by \p Fragment.
     166             :   uint64_t getFragmentInstByte(const MCPaddingFragment *Fragment,
     167             :                                MCAsmLayout &Layout) const;
     168             :   uint64_t computeWindowEndAddress(const MCPaddingFragment *Fragment,
     169             :                                    uint64_t Offset, MCAsmLayout &Layout) const;
     170             : 
     171             :   /// Computes and returns the penalty weight of a first instruction window in a
     172             :   /// range. This requires a special function since the first window does not
     173             :   /// contain all the padding fragments in that window. It only contains all the
     174             :   /// padding fragments starting from the relevant insertion point.
     175             :   ///
     176             :   /// \param Window The first window.
     177             :   /// \param Offset The offset of the parent section relative to the beginning
     178             :   /// of the file, mod the window size.
     179             :   /// \param Layout Code layout information.
     180             :   ///
     181             :   /// \returns the penalty weight of a first instruction window in a range, \p
     182             :   /// Window.
     183             :   double computeFirstWindowPenaltyWeight(const MCPFRange &Window,
     184             :                                          uint64_t Offset,
     185             :                                          MCAsmLayout &Layout) const;
     186             :   /// Computes and returns the penalty caused by an instruction window.
     187             :   ///
     188             :   /// \param Window The instruction window.
     189             :   /// \param Offset The offset of the parent section relative to the beginning
     190             :   /// of the file, mod the window size.
     191             :   /// \param Layout Code layout information.
     192             :   ///
     193             :   /// \returns the penalty caused by \p Window.
     194             :   virtual double computeWindowPenaltyWeight(const MCPFRange &Window,
     195             :                                             uint64_t Offset,
     196             :                                             MCAsmLayout &Layout) const = 0;
     197             : 
     198             : public:
     199             :   virtual ~MCCodePaddingPolicy() {}
     200             : 
     201             :   /// Returns the kind mask of this policy -  A mask holding the kind of this
     202             :   /// policy, i.e. only the i'th bit will be set where i is the kind number.
     203             :   uint64_t getKindMask() const { return KindMask; }
     204             :   /// Returns the instruction window size relevant to this policy.
     205             :   uint64_t getWindowSize() const { return WindowSize; }
     206             :   /// Returns true if the last byte of an instruction determines its instruction
     207             :   /// window, or false if the first of an instruction determines it.
     208             :   bool isInstByteLastByte() const { return InstByteIsLastByte; }
     209             : 
     210             :   /// Returns true iff this policy needs padding for a given basic block.
     211             :   ///
     212             :   /// \param Context the context of the padding, Embeds the basic block's
     213             :   /// parameters.
     214             :   ///
     215             :   /// \returns true iff this policy needs padding for the basic block.
     216             :   virtual bool
     217           0 :   basicBlockRequiresPaddingFragment(const MCCodePaddingContext &Context) const {
     218           0 :     return false;
     219             :   }
     220             :   /// Returns true iff this policy needs padding for a given instruction.
     221             :   ///
     222             :   /// \param Inst The given instruction.
     223             :   ///
     224             :   /// \returns true iff this policy needs padding for \p Inst.
     225           0 :   virtual bool instructionRequiresPaddingFragment(const MCInst &Inst) const {
     226           0 :     return false;
     227             :   }
     228             :   /// Computes and returns the penalty caused by a range of instruction windows.
     229             :   /// The weight is computed for each window separelty and then accumulated.
     230             :   ///
     231             :   /// \param Range The range.
     232             :   /// \param Offset The offset of the parent section relative to the beginning
     233             :   /// of the file, mod the window size.
     234             :   /// \param Layout Code layout information.
     235             :   ///
     236             :   /// \returns the penalty caused by \p Range.
     237             :   double computeRangePenaltyWeight(const MCPFRange &Range, uint64_t Offset,
     238             :                                    MCAsmLayout &Layout) const;
     239             : };
     240             : 
     241             : } // namespace llvm
     242             : 
     243             : #endif // LLVM_MC_MCCODEPADDER_H

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