OcamlGCPrinter.cpp revision af76e592c7f9deff0e55c13dbb4a34f07f1c7f64 
1//===-- OcamlGCPrinter.cpp - Ocaml frametable emitter ---------------------===//
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 printing the assembly code for an Ocaml frametable.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/CodeGen/GCs.h"
15#include "llvm/CodeGen/AsmPrinter.h"
16#include "llvm/CodeGen/GCMetadataPrinter.h"
17#include "llvm/Module.h"
18#include "llvm/MC/MCStreamer.h"
19#include "llvm/MC/MCAsmInfo.h"
20#include "llvm/Target/TargetData.h"
21#include "llvm/Target/TargetLoweringObjectFile.h"
22#include "llvm/Target/TargetMachine.h"
23#include "llvm/Support/Compiler.h"
24#include "llvm/Support/ErrorHandling.h"
25#include "llvm/Support/raw_ostream.h"
26using namespace llvm;
27
28namespace {
29
30  class VISIBILITY_HIDDEN OcamlGCMetadataPrinter : public GCMetadataPrinter {
31  public:
32    void beginAssembly(raw_ostream &OS, AsmPrinter &AP,
33                       const MCAsmInfo &TAI);
34
35    void finishAssembly(raw_ostream &OS, AsmPrinter &AP,
36                        const MCAsmInfo &TAI);
37  };
38
39}
40
41static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
42Y("ocaml", "ocaml 3.10-compatible collector");
43
44void llvm::linkOcamlGCPrinter() { }
45
46static void EmitCamlGlobal(const Module &M, raw_ostream &OS, AsmPrinter &AP,
47                           const MCAsmInfo &TAI, const char *Id) {
48  const std::string &MId = M.getModuleIdentifier();
49
50  std::string Mangled;
51  Mangled += TAI.getGlobalPrefix();
52  Mangled += "caml";
53  size_t Letter = Mangled.size();
54  Mangled.append(MId.begin(), std::find(MId.begin(), MId.end(), '.'));
55  Mangled += "__";
56  Mangled += Id;
57
58  // Capitalize the first letter of the module name.
59  Mangled[Letter] = toupper(Mangled[Letter]);
60
61  if (const char *GlobalDirective = TAI.getGlobalDirective())
62    OS << GlobalDirective << Mangled << "\n";
63  OS << Mangled << ":\n";
64}
65
66void OcamlGCMetadataPrinter::beginAssembly(raw_ostream &OS, AsmPrinter &AP,
67                                           const MCAsmInfo &TAI) {
68  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
69  EmitCamlGlobal(getModule(), OS, AP, TAI, "code_begin");
70
71  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
72  EmitCamlGlobal(getModule(), OS, AP, TAI, "data_begin");
73}
74
75/// emitAssembly - Print the frametable. The ocaml frametable format is thus:
76///
77///   extern "C" struct align(sizeof(intptr_t)) {
78///     uint16_t NumDescriptors;
79///     struct align(sizeof(intptr_t)) {
80///       void *ReturnAddress;
81///       uint16_t FrameSize;
82///       uint16_t NumLiveOffsets;
83///       uint16_t LiveOffsets[NumLiveOffsets];
84///     } Descriptors[NumDescriptors];
85///   } caml${module}__frametable;
86///
87/// Note that this precludes programs from stack frames larger than 64K
88/// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
89/// either condition is detected in a function which uses the GC.
90///
91void OcamlGCMetadataPrinter::finishAssembly(raw_ostream &OS, AsmPrinter &AP,
92                                            const MCAsmInfo &TAI) {
93  const char *AddressDirective;
94  int AddressAlignLog;
95  if (AP.TM.getTargetData()->getPointerSize() == sizeof(int32_t)) {
96    AddressDirective = TAI.getData32bitsDirective();
97    AddressAlignLog = 2;
98  } else {
99    AddressDirective = TAI.getData64bitsDirective();
100    AddressAlignLog = 3;
101  }
102
103  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
104  EmitCamlGlobal(getModule(), OS, AP, TAI, "code_end");
105
106  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
107  EmitCamlGlobal(getModule(), OS, AP, TAI, "data_end");
108
109  OS << AddressDirective << 0; // FIXME: Why does ocaml emit this??
110  AP.EOL();
111
112  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
113  EmitCamlGlobal(getModule(), OS, AP, TAI, "frametable");
114
115  for (iterator I = begin(), IE = end(); I != IE; ++I) {
116    GCFunctionInfo &FI = **I;
117
118    uint64_t FrameSize = FI.getFrameSize();
119    if (FrameSize >= 1<<16) {
120      std::string msg;
121      raw_string_ostream Msg(msg);
122      Msg << "Function '" << FI.getFunction().getName()
123           << "' is too large for the ocaml GC! "
124           << "Frame size " << FrameSize << " >= 65536.\n";
125      Msg << "(" << uintptr_t(&FI) << ")";
126      llvm_report_error(Msg.str()); // Very rude!
127    }
128
129    OS << "\t" << TAI.getCommentString() << " live roots for "
130       << FI.getFunction().getName() << "\n";
131
132    for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
133      size_t LiveCount = FI.live_size(J);
134      if (LiveCount >= 1<<16) {
135        std::string msg;
136        raw_string_ostream Msg(msg);
137        Msg << "Function '" << FI.getFunction().getName()
138             << "' is too large for the ocaml GC! "
139             << "Live root count " << LiveCount << " >= 65536.";
140        llvm_report_error(Msg.str()); // Very rude!
141      }
142
143      OS << AddressDirective
144         << TAI.getPrivateGlobalPrefix() << "label" << J->Num;
145      AP.EOL("call return address");
146
147      AP.EmitInt16(FrameSize);
148      AP.EOL("stack frame size");
149
150      AP.EmitInt16(LiveCount);
151      AP.EOL("live root count");
152
153      for (GCFunctionInfo::live_iterator K = FI.live_begin(J),
154                                         KE = FI.live_end(J); K != KE; ++K) {
155        assert(K->StackOffset < 1<<16 &&
156               "GC root stack offset is outside of fixed stack frame and out "
157               "of range for ocaml GC!");
158
159        OS << "\t.word\t" << K->StackOffset;
160        AP.EOL("stack offset");
161      }
162
163      AP.EmitAlignment(AddressAlignLog);
164    }
165  }
166}
167