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