OcamlGCPrinter.cpp revision cb3718832375a581c5ea23f15918f3ea447a446c 
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/Support/raw_ostream.h"
19#include "llvm/Target/TargetAsmInfo.h"
20#include "llvm/Target/TargetData.h"
21#include "llvm/Target/TargetMachine.h"
22
23using namespace llvm;
24
25namespace {
26
27  class VISIBILITY_HIDDEN OcamlGCMetadataPrinter : public GCMetadataPrinter {
28  public:
29    void beginAssembly(raw_ostream &OS, AsmPrinter &AP,
30                       const TargetAsmInfo &TAI);
31
32    void finishAssembly(raw_ostream &OS, AsmPrinter &AP,
33                        const TargetAsmInfo &TAI);
34  };
35
36}
37
38static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
39Y("ocaml", "ocaml 3.10-compatible collector");
40
41void llvm::linkOcamlGCPrinter() { }
42
43static void EmitCamlGlobal(const Module &M, raw_ostream &OS, AsmPrinter &AP,
44                           const TargetAsmInfo &TAI, const char *Id) {
45  const std::string &MId = M.getModuleIdentifier();
46
47  std::string Mangled;
48  Mangled += TAI.getGlobalPrefix();
49  Mangled += "caml";
50  size_t Letter = Mangled.size();
51  Mangled.append(MId.begin(), std::find(MId.begin(), MId.end(), '.'));
52  Mangled += "__";
53  Mangled += Id;
54
55  // Capitalize the first letter of the module name.
56  Mangled[Letter] = toupper(Mangled[Letter]);
57
58  if (const char *GlobalDirective = TAI.getGlobalDirective())
59    OS << GlobalDirective << Mangled << "\n";
60  OS << Mangled << ":\n";
61}
62
63void OcamlGCMetadataPrinter::beginAssembly(raw_ostream &OS, AsmPrinter &AP,
64                                           const TargetAsmInfo &TAI) {
65  AP.SwitchToTextSection(TAI.getTextSection());
66  EmitCamlGlobal(getModule(), OS, AP, TAI, "code_begin");
67
68  AP.SwitchToDataSection(TAI.getDataSection());
69  EmitCamlGlobal(getModule(), OS, AP, TAI, "data_begin");
70}
71
72/// emitAssembly - Print the frametable. The ocaml frametable format is thus:
73///
74///   extern "C" struct align(sizeof(intptr_t)) {
75///     uint16_t NumDescriptors;
76///     struct align(sizeof(intptr_t)) {
77///       void *ReturnAddress;
78///       uint16_t FrameSize;
79///       uint16_t NumLiveOffsets;
80///       uint16_t LiveOffsets[NumLiveOffsets];
81///     } Descriptors[NumDescriptors];
82///   } caml${module}__frametable;
83///
84/// Note that this precludes programs from stack frames larger than 64K
85/// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
86/// either condition is detected in a function which uses the GC.
87///
88void OcamlGCMetadataPrinter::finishAssembly(raw_ostream &OS, AsmPrinter &AP,
89                                            const TargetAsmInfo &TAI) {
90  const char *AddressDirective;
91  int AddressAlignLog;
92  if (AP.TM.getTargetData()->getPointerSize() == sizeof(int32_t)) {
93    AddressDirective = TAI.getData32bitsDirective();
94    AddressAlignLog = 2;
95  } else {
96    AddressDirective = TAI.getData64bitsDirective();
97    AddressAlignLog = 3;
98  }
99
100  AP.SwitchToTextSection(TAI.getTextSection());
101  EmitCamlGlobal(getModule(), OS, AP, TAI, "code_end");
102
103  AP.SwitchToDataSection(TAI.getDataSection());
104  EmitCamlGlobal(getModule(), OS, AP, TAI, "data_end");
105
106  OS << AddressDirective << 0; // FIXME: Why does ocaml emit this??
107  AP.EOL();
108
109  AP.SwitchToDataSection(TAI.getDataSection());
110  EmitCamlGlobal(getModule(), OS, AP, TAI, "frametable");
111
112  for (iterator I = begin(), IE = end(); I != IE; ++I) {
113    GCFunctionInfo &FI = **I;
114
115    uint64_t FrameSize = FI.getFrameSize();
116    if (FrameSize >= 1<<16) {
117      cerr << "Function '" << FI.getFunction().getNameStart()
118           << "' is too large for the ocaml GC! "
119           << "Frame size " << FrameSize << " >= 65536.\n";
120      cerr << "(" << uintptr_t(&FI) << ")\n";
121      abort(); // Very rude!
122    }
123
124    OS << "\t" << TAI.getCommentString() << " live roots for "
125       << FI.getFunction().getNameStart() << "\n";
126
127    for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
128      size_t LiveCount = FI.live_size(J);
129      if (LiveCount >= 1<<16) {
130        cerr << "Function '" << FI.getFunction().getNameStart()
131             << "' is too large for the ocaml GC! "
132             << "Live root count " << LiveCount << " >= 65536.\n";
133        abort(); // Very rude!
134      }
135
136      OS << AddressDirective
137         << TAI.getPrivateGlobalPrefix() << "label" << J->Num;
138      AP.EOL("call return address");
139
140      AP.EmitInt16(FrameSize);
141      AP.EOL("stack frame size");
142
143      AP.EmitInt16(LiveCount);
144      AP.EOL("live root count");
145
146      for (GCFunctionInfo::live_iterator K = FI.live_begin(J),
147                                         KE = FI.live_end(J); K != KE; ++K) {
148        assert(K->StackOffset < 1<<16 &&
149               "GC root stack offset is outside of fixed stack frame and out "
150               "of range for ocaml GC!");
151
152        OS << "\t.word\t" << K->StackOffset;
153        AP.EOL("stack offset");
154      }
155
156      AP.EmitAlignment(AddressAlignLog);
157    }
158  }
159}
160