llvm/lib/MC/ConstantPools.cpp

   1 //===- ConstantPools.cpp - ConstantPool class -----------------------------===//
   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 implements the ConstantPool and  AssemblerConstantPools classes.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/MC/ConstantPools.h"
  14 #include "llvm/MC/MCContext.h"
  15 #include "llvm/MC/MCDirectives.h"
  16 #include "llvm/MC/MCExpr.h"
  17 #include "llvm/MC/MCStreamer.h"
  18 #include "llvm/Support/Casting.h"
  19
  20 using namespace llvm;
  21
  22 //
  23 // ConstantPool implementation
  24 //
  25 // Emit the contents of the constant pool using the provided streamer.
  26 void ConstantPool::emitEntries(MCStreamer &Streamer) {
  27   if (Entries.empty())
  28     return;
  29   Streamer.emitDataRegion(MCDR_DataRegion);
  30   for (const ConstantPoolEntry &Entry : Entries) {
  31     Streamer.emitValueToAlignment(Align(Entry.Size)); // align naturally
  32     Streamer.emitLabel(Entry.Label);
  33     Streamer.emitValue(Entry.Value, Entry.Size, Entry.Loc);
  34   }
  35   Streamer.emitDataRegion(MCDR_DataRegionEnd);
  36   Entries.clear();
  37 }
  38
  39 const MCExpr *ConstantPool::addEntry(const MCExpr *Value, MCContext &Context,
  40                                      unsigned Size, SMLoc Loc) {
  41   const MCConstantExpr *C = dyn_cast<MCConstantExpr>(Value);
  42   const MCSymbolRefExpr *S = dyn_cast<MCSymbolRefExpr>(Value);
  43
  44   // Check if there is existing entry for the same constant. If so, reuse it.
  45   if (C) {
  46     auto CItr = CachedConstantEntries.find(C->getValue());
  47     if (CItr != CachedConstantEntries.end())
  48       return CItr->second;
  49   }
  50
  51   // Check if there is existing entry for the same symbol. If so, reuse it.
  52   if (S) {
  53     auto SItr = CachedSymbolEntries.find(&(S->getSymbol()));
  54     if (SItr != CachedSymbolEntries.end())
  55       return SItr->second;
  56   }
  57
  58   MCSymbol *CPEntryLabel = Context.createTempSymbol();
  59
  60   Entries.push_back(ConstantPoolEntry(CPEntryLabel, Value, Size, Loc));
  61   const auto SymRef = MCSymbolRefExpr::create(CPEntryLabel, Context);
  62   if (C)
  63     CachedConstantEntries[C->getValue()] = SymRef;
  64   if (S)
  65     CachedSymbolEntries[&(S->getSymbol())] = SymRef;
  66   return SymRef;
  67 }
  68
  69 bool ConstantPool::empty() { return Entries.empty(); }
  70
  71 void ConstantPool::clearCache() {
  72   CachedConstantEntries.clear();
  73   CachedSymbolEntries.clear();
  74 }
  75
  76 //
  77 // AssemblerConstantPools implementation
  78 //
  79 ConstantPool *AssemblerConstantPools::getConstantPool(MCSection *Section) {
  80   ConstantPoolMapTy::iterator CP = ConstantPools.find(Section);
  81   if (CP == ConstantPools.end())
  82     return nullptr;
  83
  84   return &CP->second;
  85 }
  86
  87 ConstantPool &
  88 AssemblerConstantPools::getOrCreateConstantPool(MCSection *Section) {
  89   return ConstantPools[Section];
  90 }
  91
  92 static void emitConstantPool(MCStreamer &Streamer, MCSection *Section,
  93                              ConstantPool &CP) {
  94   if (!CP.empty()) {
  95     Streamer.switchSection(Section);
  96     CP.emitEntries(Streamer);
  97   }
  98 }
  99
 100 void AssemblerConstantPools::emitAll(MCStreamer &Streamer) {
 101   // Dump contents of assembler constant pools.
 102   for (auto &CPI : ConstantPools) {
 103     MCSection *Section = CPI.first;
 104     ConstantPool &CP = CPI.second;
 105
 106     emitConstantPool(Streamer, Section, CP);
 107   }
 108 }
 109
 110 void AssemblerConstantPools::emitForCurrentSection(MCStreamer &Streamer) {
 111   MCSection *Section = Streamer.getCurrentSectionOnly();
 112   if (ConstantPool *CP = getConstantPool(Section))
 113     emitConstantPool(Streamer, Section, *CP);
 114 }
 115
 116 void AssemblerConstantPools::clearCacheForCurrentSection(MCStreamer &Streamer) {
 117   MCSection *Section = Streamer.getCurrentSectionOnly();
 118   if (ConstantPool *CP = getConstantPool(Section))
 119     CP->clearCache();
 120 }
 121
 122 const MCExpr *AssemblerConstantPools::addEntry(MCStreamer &Streamer,
 123                                                const MCExpr *Expr,
 124                                                unsigned Size, SMLoc Loc) {
 125   MCSection *Section = Streamer.getCurrentSectionOnly();
 126   return getOrCreateConstantPool(Section).addEntry(Expr, Streamer.getContext(),
 127                                                    Size, Loc);
 128 }