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.EmitCodeAlignment(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
  43   // Check if there is existing entry for the same constant. If so, reuse it.
  44   auto Itr = C ? CachedEntries.find(C->getValue()) : CachedEntries.end();
  45   if (Itr != CachedEntries.end())
  46     return Itr->second;
  47
  48   MCSymbol *CPEntryLabel = Context.createTempSymbol();
  49
  50   Entries.push_back(ConstantPoolEntry(CPEntryLabel, Value, Size, Loc));
  51   const auto SymRef = MCSymbolRefExpr::create(CPEntryLabel, Context);
  52   if (C)
  53     CachedEntries[C->getValue()] = SymRef;
  54   return SymRef;
  55 }
  56
  57 bool ConstantPool::empty() { return Entries.empty(); }
  58
  59 void ConstantPool::clearCache() {
  60   CachedEntries.clear();
  61 }
  62
  63 //
  64 // AssemblerConstantPools implementation
  65 //
  66 ConstantPool *AssemblerConstantPools::getConstantPool(MCSection *Section) {
  67   ConstantPoolMapTy::iterator CP = ConstantPools.find(Section);
  68   if (CP == ConstantPools.end())
  69     return nullptr;
  70
  71   return &CP->second;
  72 }
  73
  74 ConstantPool &
  75 AssemblerConstantPools::getOrCreateConstantPool(MCSection *Section) {
  76   return ConstantPools[Section];
  77 }
  78
  79 static void emitConstantPool(MCStreamer &Streamer, MCSection *Section,
  80                              ConstantPool &CP) {
  81   if (!CP.empty()) {
  82     Streamer.SwitchSection(Section);
  83     CP.emitEntries(Streamer);
  84   }
  85 }
  86
  87 void AssemblerConstantPools::emitAll(MCStreamer &Streamer) {
  88   // Dump contents of assembler constant pools.
  89   for (auto &CPI : ConstantPools) {
  90     MCSection *Section = CPI.first;
  91     ConstantPool &CP = CPI.second;
  92
  93     emitConstantPool(Streamer, Section, CP);
  94   }
  95 }
  96
  97 void AssemblerConstantPools::emitForCurrentSection(MCStreamer &Streamer) {
  98   MCSection *Section = Streamer.getCurrentSectionOnly();
  99   if (ConstantPool *CP = getConstantPool(Section))
 100     emitConstantPool(Streamer, Section, *CP);
 101 }
 102
 103 void AssemblerConstantPools::clearCacheForCurrentSection(MCStreamer &Streamer) {
 104   MCSection *Section = Streamer.getCurrentSectionOnly();
 105   if (ConstantPool *CP = getConstantPool(Section))
 106     CP->clearCache();
 107 }
 108
 109 const MCExpr *AssemblerConstantPools::addEntry(MCStreamer &Streamer,
 110                                                const MCExpr *Expr,
 111                                                unsigned Size, SMLoc Loc) {
 112   MCSection *Section = Streamer.getCurrentSectionOnly();
 113   return getOrCreateConstantPool(Section).addEntry(Expr, Streamer.getContext(),
 114                                                    Size, Loc);
 115 }