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  1. //===- ConstantPools.h - Keep track of assembler-generated ------*- C++ -*-===//
  2. //
  3. // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  4. // See https://llvm.org/LICENSE.txt for license information.
  5. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  6. //
  7. //===----------------------------------------------------------------------===//
  8. //
  9. // This file declares the ConstantPool and AssemblerConstantPools classes.
  10. //
  11. //===----------------------------------------------------------------------===//
  12.  
  13. #ifndef LLVM_MC_CONSTANTPOOLS_H
  14. #define LLVM_MC_CONSTANTPOOLS_H
  15.  
  16. #include "llvm/ADT/MapVector.h"
  17. #include "llvm/ADT/SmallVector.h"
  18. #include "llvm/Support/SMLoc.h"
  19. #include <cstdint>
  20. #include <map>
  21.  
  22. namespace llvm {
  23.  
  24. class MCContext;
  25. class MCExpr;
  26. class MCSection;
  27. class MCStreamer;
  28. class MCSymbol;
  29. class MCSymbolRefExpr;
  30.  
  31. struct ConstantPoolEntry {
  32.   ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
  33.     : Label(L), Value(Val), Size(Sz), Loc(Loc_) {}
  34.  
  35.   MCSymbol *Label;
  36.   const MCExpr *Value;
  37.   unsigned Size;
  38.   SMLoc Loc;
  39. };
  40.  
  41. // A class to keep track of assembler-generated constant pools that are use to
  42. // implement the ldr-pseudo.
  43. class ConstantPool {
  44.   using EntryVecTy = SmallVector<ConstantPoolEntry, 4>;
  45.   EntryVecTy Entries;
  46.   std::map<int64_t, const MCSymbolRefExpr *> CachedConstantEntries;
  47.   DenseMap<const MCSymbol *, const MCSymbolRefExpr *> CachedSymbolEntries;
  48.  
  49. public:
  50.   // Initialize a new empty constant pool
  51.   ConstantPool() = default;
  52.  
  53.   // Add a new entry to the constant pool in the next slot.
  54.   // \param Value is the new entry to put in the constant pool.
  55.   // \param Size is the size in bytes of the entry
  56.   //
  57.   // \returns a MCExpr that references the newly inserted value
  58.   const MCExpr *addEntry(const MCExpr *Value, MCContext &Context,
  59.                          unsigned Size, SMLoc Loc);
  60.  
  61.   // Emit the contents of the constant pool using the provided streamer.
  62.   void emitEntries(MCStreamer &Streamer);
  63.  
  64.   // Return true if the constant pool is empty
  65.   bool empty();
  66.  
  67.   void clearCache();
  68. };
  69.  
  70. class AssemblerConstantPools {
  71.   // Map type used to keep track of per-Section constant pools used by the
  72.   // ldr-pseudo opcode. The map associates a section to its constant pool. The
  73.   // constant pool is a vector of (label, value) pairs. When the ldr
  74.   // pseudo is parsed we insert a new (label, value) pair into the constant pool
  75.   // for the current section and add MCSymbolRefExpr to the new label as
  76.   // an opcode to the ldr. After we have parsed all the user input we
  77.   // output the (label, value) pairs in each constant pool at the end of the
  78.   // section.
  79.   //
  80.   // We use the MapVector for the map type to ensure stable iteration of
  81.   // the sections at the end of the parse. We need to iterate over the
  82.   // sections in a stable order to ensure that we have print the
  83.   // constant pools in a deterministic order when printing an assembly
  84.   // file.
  85.   using ConstantPoolMapTy = MapVector<MCSection *, ConstantPool>;
  86.   ConstantPoolMapTy ConstantPools;
  87.  
  88. public:
  89.   void emitAll(MCStreamer &Streamer);
  90.   void emitForCurrentSection(MCStreamer &Streamer);
  91.   void clearCacheForCurrentSection(MCStreamer &Streamer);
  92.   const MCExpr *addEntry(MCStreamer &Streamer, const MCExpr *Expr,
  93.                          unsigned Size, SMLoc Loc);
  94.  
  95. private:
  96.   ConstantPool *getConstantPool(MCSection *Section);
  97.   ConstantPool &getOrCreateConstantPool(MCSection *Section);
  98. };
  99.  
  100. } // end namespace llvm
  101.  
  102. #endif // LLVM_MC_CONSTANTPOOLS_H
  103.