OcamlGCPrinter.cpp revision d04a8d4b33ff316ca4cf961e06c9e312eff8e64f 
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/ADT/SmallString.h"
16#include "llvm/CodeGen/AsmPrinter.h"
17#include "llvm/CodeGen/GCMetadataPrinter.h"
18#include "llvm/DataLayout.h"
19#include "llvm/MC/MCAsmInfo.h"
20#include "llvm/MC/MCContext.h"
21#include "llvm/MC/MCStreamer.h"
22#include "llvm/MC/MCSymbol.h"
23#include "llvm/Module.h"
24#include "llvm/Support/ErrorHandling.h"
25#include "llvm/Support/FormattedStream.h"
26#include "llvm/Target/Mangler.h"
27#include "llvm/Target/TargetLoweringObjectFile.h"
28#include "llvm/Target/TargetMachine.h"
29#include <cctype>
30using namespace llvm;
31
32namespace {
33
34  class OcamlGCMetadataPrinter : public GCMetadataPrinter {
35  public:
36    void beginAssembly(AsmPrinter &AP);
37    void finishAssembly(AsmPrinter &AP);
38  };
39
40}
41
42static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
43Y("ocaml", "ocaml 3.10-compatible collector");
44
45void llvm::linkOcamlGCPrinter() { }
46
47static void EmitCamlGlobal(const Module &M, AsmPrinter &AP, const char *Id) {
48  const std::string &MId = M.getModuleIdentifier();
49
50  std::string SymName;
51  SymName += "caml";
52  size_t Letter = SymName.size();
53  SymName.append(MId.begin(), std::find(MId.begin(), MId.end(), '.'));
54  SymName += "__";
55  SymName += Id;
56
57  // Capitalize the first letter of the module name.
58  SymName[Letter] = toupper(SymName[Letter]);
59
60  SmallString<128> TmpStr;
61  AP.Mang->getNameWithPrefix(TmpStr, SymName);
62
63  MCSymbol *Sym = AP.OutContext.GetOrCreateSymbol(TmpStr);
64
65  AP.OutStreamer.EmitSymbolAttribute(Sym, MCSA_Global);
66  AP.OutStreamer.EmitLabel(Sym);
67}
68
69void OcamlGCMetadataPrinter::beginAssembly(AsmPrinter &AP) {
70  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
71  EmitCamlGlobal(getModule(), AP, "code_begin");
72
73  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
74  EmitCamlGlobal(getModule(), AP, "data_begin");
75}
76
77/// emitAssembly - Print the frametable. The ocaml frametable format is thus:
78///
79///   extern "C" struct align(sizeof(intptr_t)) {
80///     uint16_t NumDescriptors;
81///     struct align(sizeof(intptr_t)) {
82///       void *ReturnAddress;
83///       uint16_t FrameSize;
84///       uint16_t NumLiveOffsets;
85///       uint16_t LiveOffsets[NumLiveOffsets];
86///     } Descriptors[NumDescriptors];
87///   } caml${module}__frametable;
88///
89/// Note that this precludes programs from stack frames larger than 64K
90/// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
91/// either condition is detected in a function which uses the GC.
92///
93void OcamlGCMetadataPrinter::finishAssembly(AsmPrinter &AP) {
94  unsigned IntPtrSize = AP.TM.getDataLayout()->getPointerSize();
95
96  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
97  EmitCamlGlobal(getModule(), AP, "code_end");
98
99  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
100  EmitCamlGlobal(getModule(), AP, "data_end");
101
102  // FIXME: Why does ocaml emit this??
103  AP.OutStreamer.EmitIntValue(0, IntPtrSize, 0);
104
105  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
106  EmitCamlGlobal(getModule(), AP, "frametable");
107
108  int NumDescriptors = 0;
109  for (iterator I = begin(), IE = end(); I != IE; ++I) {
110    GCFunctionInfo &FI = **I;
111    for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
112      NumDescriptors++;
113    }
114  }
115
116  if (NumDescriptors >= 1<<16) {
117    // Very rude!
118    report_fatal_error(" Too much descriptor for ocaml GC");
119  }
120  AP.EmitInt16(NumDescriptors);
121  AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
122
123  for (iterator I = begin(), IE = end(); I != IE; ++I) {
124    GCFunctionInfo &FI = **I;
125
126    uint64_t FrameSize = FI.getFrameSize();
127    if (FrameSize >= 1<<16) {
128      // Very rude!
129      report_fatal_error("Function '" + FI.getFunction().getName() +
130                         "' is too large for the ocaml GC! "
131                         "Frame size " + Twine(FrameSize) + ">= 65536.\n"
132                         "(" + Twine(uintptr_t(&FI)) + ")");
133    }
134
135    AP.OutStreamer.AddComment("live roots for " +
136                              Twine(FI.getFunction().getName()));
137    AP.OutStreamer.AddBlankLine();
138
139    for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
140      size_t LiveCount = FI.live_size(J);
141      if (LiveCount >= 1<<16) {
142        // Very rude!
143        report_fatal_error("Function '" + FI.getFunction().getName() +
144                           "' is too large for the ocaml GC! "
145                           "Live root count "+Twine(LiveCount)+" >= 65536.");
146      }
147
148      AP.OutStreamer.EmitSymbolValue(J->Label, IntPtrSize, 0);
149      AP.EmitInt16(FrameSize);
150      AP.EmitInt16(LiveCount);
151
152      for (GCFunctionInfo::live_iterator K = FI.live_begin(J),
153                                         KE = FI.live_end(J); K != KE; ++K) {
154        if (K->StackOffset >= 1<<16) {
155          // Very rude!
156          report_fatal_error(
157                 "GC root stack offset is outside of fixed stack frame and out "
158                 "of range for ocaml GC!");
159        }
160        AP.EmitInt16(K->StackOffset);
161      }
162
163      AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
164    }
165  }
166}
167