include/llvm/MC/ConstantPools.h

   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/DenseMap.h"
  17 #include "llvm/ADT/MapVector.h"
  18 #include "llvm/ADT/SmallVector.h"
  19 #include "llvm/Support/SMLoc.h"
  20 #include <cstdint>
  21 #include <map>
  22
  23 namespace llvm {
  24
  25 class MCContext;
  26 class MCExpr;
  27 class MCSection;
  28 class MCStreamer;
  29 class MCSymbol;
  30 class MCSymbolRefExpr;
  31
  32 struct ConstantPoolEntry {
  33   ConstantPoolEntry(MCSymbol *L, const MCExpr *Val, unsigned Sz, SMLoc Loc_)
  34     : Label(L), Value(Val), Size(Sz), Loc(Loc_) {}
  35
  36   MCSymbol *Label;
  37   const MCExpr *Value;
  38   unsigned Size;
  39   SMLoc Loc;
  40 };
  41
  42 // A class to keep track of assembler-generated constant pools that are use to
  43 // implement the ldr-pseudo.
  44 class ConstantPool {
  45   using EntryVecTy = SmallVector<ConstantPoolEntry, 4>;
  46   EntryVecTy Entries;
  47   std::map<int64_t, const MCSymbolRefExpr *> CachedEntries;
  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