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/IR/DataLayout.h"
19 #include "llvm/IR/Mangler.h"
20 #include "llvm/IR/Module.h"
21 #include "llvm/MC/MCAsmInfo.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCStreamer.h"
24 #include "llvm/MC/MCSymbol.h"
25 #include "llvm/Support/ErrorHandling.h"
26 #include "llvm/Support/FormattedStream.h"
27 #include "llvm/Target/TargetLoweringObjectFile.h"
28 #include "llvm/Target/TargetMachine.h"
29 #include "llvm/Target/TargetSubtargetInfo.h"
30 #include <cctype>
31 using namespace llvm;
32
33 namespace {
34
35 class OcamlGCMetadataPrinter : public GCMetadataPrinter {
36 public:
37 void beginAssembly(Module &M, GCModuleInfo &Info,
38 AsmPrinter &AP) override;
39 void finishAssembly(Module &M, GCModuleInfo &Info,
40 AsmPrinter &AP) override;
41 };
42
43 }
44
45 static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
46 Y("ocaml", "ocaml 3.10-compatible collector");
47
linkOcamlGCPrinter()48 void llvm::linkOcamlGCPrinter() { }
49
EmitCamlGlobal(const Module & M,AsmPrinter & AP,const char * Id)50 static void EmitCamlGlobal(const Module &M, AsmPrinter &AP, const char *Id) {
51 const std::string &MId = M.getModuleIdentifier();
52
53 std::string SymName;
54 SymName += "caml";
55 size_t Letter = SymName.size();
56 SymName.append(MId.begin(), std::find(MId.begin(), MId.end(), '.'));
57 SymName += "__";
58 SymName += Id;
59
60 // Capitalize the first letter of the module name.
61 SymName[Letter] = toupper(SymName[Letter]);
62
63 SmallString<128> TmpStr;
64 AP.Mang->getNameWithPrefix(TmpStr, SymName);
65
66 MCSymbol *Sym = AP.OutContext.GetOrCreateSymbol(TmpStr);
67
68 AP.OutStreamer.EmitSymbolAttribute(Sym, MCSA_Global);
69 AP.OutStreamer.EmitLabel(Sym);
70 }
71
beginAssembly(Module & M,GCModuleInfo & Info,AsmPrinter & AP)72 void OcamlGCMetadataPrinter::beginAssembly(Module &M, GCModuleInfo &Info,
73 AsmPrinter &AP) {
74 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
75 EmitCamlGlobal(M, AP, "code_begin");
76
77 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
78 EmitCamlGlobal(M, AP, "data_begin");
79 }
80
81 /// emitAssembly - Print the frametable. The ocaml frametable format is thus:
82 ///
83 /// extern "C" struct align(sizeof(intptr_t)) {
84 /// uint16_t NumDescriptors;
85 /// struct align(sizeof(intptr_t)) {
86 /// void *ReturnAddress;
87 /// uint16_t FrameSize;
88 /// uint16_t NumLiveOffsets;
89 /// uint16_t LiveOffsets[NumLiveOffsets];
90 /// } Descriptors[NumDescriptors];
91 /// } caml${module}__frametable;
92 ///
93 /// Note that this precludes programs from stack frames larger than 64K
94 /// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
95 /// either condition is detected in a function which uses the GC.
96 ///
finishAssembly(Module & M,GCModuleInfo & Info,AsmPrinter & AP)97 void OcamlGCMetadataPrinter::finishAssembly(Module &M, GCModuleInfo &Info,
98 AsmPrinter &AP) {
99 unsigned IntPtrSize =
100 AP.TM.getSubtargetImpl()->getDataLayout()->getPointerSize();
101
102 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
103 EmitCamlGlobal(M, AP, "code_end");
104
105 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
106 EmitCamlGlobal(M, AP, "data_end");
107
108 // FIXME: Why does ocaml emit this??
109 AP.OutStreamer.EmitIntValue(0, IntPtrSize);
110
111 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
112 EmitCamlGlobal(M, AP, "frametable");
113
114 int NumDescriptors = 0;
115 for (GCModuleInfo::FuncInfoVec::iterator I = Info.funcinfo_begin(),
116 IE = Info.funcinfo_end(); I != IE; ++I) {
117 GCFunctionInfo &FI = **I;
118 if (FI.getStrategy().getName() != getStrategy().getName())
119 // this function is managed by some other GC
120 continue;
121 for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
122 NumDescriptors++;
123 }
124 }
125
126 if (NumDescriptors >= 1<<16) {
127 // Very rude!
128 report_fatal_error(" Too much descriptor for ocaml GC");
129 }
130 AP.EmitInt16(NumDescriptors);
131 AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
132
133 for (GCModuleInfo::FuncInfoVec::iterator I = Info.funcinfo_begin(),
134 IE = Info.funcinfo_end(); I != IE; ++I) {
135 GCFunctionInfo &FI = **I;
136 if (FI.getStrategy().getName() != getStrategy().getName())
137 // this function is managed by some other GC
138 continue;
139
140 uint64_t FrameSize = FI.getFrameSize();
141 if (FrameSize >= 1<<16) {
142 // Very rude!
143 report_fatal_error("Function '" + FI.getFunction().getName() +
144 "' is too large for the ocaml GC! "
145 "Frame size " + Twine(FrameSize) + ">= 65536.\n"
146 "(" + Twine(uintptr_t(&FI)) + ")");
147 }
148
149 AP.OutStreamer.AddComment("live roots for " +
150 Twine(FI.getFunction().getName()));
151 AP.OutStreamer.AddBlankLine();
152
153 for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
154 size_t LiveCount = FI.live_size(J);
155 if (LiveCount >= 1<<16) {
156 // Very rude!
157 report_fatal_error("Function '" + FI.getFunction().getName() +
158 "' is too large for the ocaml GC! "
159 "Live root count "+Twine(LiveCount)+" >= 65536.");
160 }
161
162 AP.OutStreamer.EmitSymbolValue(J->Label, IntPtrSize);
163 AP.EmitInt16(FrameSize);
164 AP.EmitInt16(LiveCount);
165
166 for (GCFunctionInfo::live_iterator K = FI.live_begin(J),
167 KE = FI.live_end(J); K != KE; ++K) {
168 if (K->StackOffset >= 1<<16) {
169 // Very rude!
170 report_fatal_error(
171 "GC root stack offset is outside of fixed stack frame and out "
172 "of range for ocaml GC!");
173 }
174 AP.EmitInt16(K->StackOffset);
175 }
176
177 AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
178 }
179 }
180 }
181