LLVM: lib/CodeGen/AsmPrinter/OcamlGCPrinter.cpp Source File

LLVM 22.0.0git
OcamlGCPrinter.cpp
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1//===- OcamlGCPrinter.cpp - Ocaml frametable emitter ----------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements printing the assembly code for an Ocaml frametable.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/ADT/STLExtras.h"
14#include "llvm/ADT/SmallString.h"
15#include "llvm/ADT/Twine.h"
16#include "llvm/CodeGen/AsmPrinter.h"
17#include "llvm/CodeGen/GCMetadata.h"
18#include "llvm/CodeGen/GCMetadataPrinter.h"
19#include "llvm/IR/BuiltinGCs.h"
20#include "llvm/IR/DataLayout.h"
21#include "llvm/IR/Function.h"
22#include "llvm/IR/Mangler.h"
23#include "llvm/IR/Module.h"
24#include "llvm/MC/MCContext.h"
25#include "llvm/MC/MCDirectives.h"
26#include "llvm/MC/MCStreamer.h"
27#include "llvm/Support/ErrorHandling.h"
28#include "llvm/Target/TargetLoweringObjectFile.h"
29#include <cctype>
30#include <cstddef>
31#include <cstdint>
32#include <string>
33
34using namespace llvm;
35
36namespace {
37
38class OcamlGCMetadataPrinter : public GCMetadataPrinter {
39public:
40 void beginAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override;
41 void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override;
42};
43
44} // end anonymous namespace
45
46static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
47 Y("ocaml", "ocaml 3.10-compatible collector");
48
49 void llvm::linkOcamlGCPrinter() {}
50
51 static void EmitCamlGlobal(const Module &M, AsmPrinter &AP, const char *Id) {
52 const std::string &MId = M.getModuleIdentifier();
53
54 std::string SymName;
55 SymName += "caml";
56 size_t Letter = SymName.size();
57 SymName.append(MId.begin(), llvm::find(MId, '.'));
58 SymName += "__";
59 SymName += Id;
60
61 // Capitalize the first letter of the module name.
62 SymName[Letter] = toupper(SymName[Letter]);
63
64 SmallString<128> TmpStr;
65 Mangler::getNameWithPrefix(TmpStr, SymName, M.getDataLayout());
66
67 MCSymbol *Sym = AP.OutContext.getOrCreateSymbol(TmpStr);
68
69 AP.OutStreamer->emitSymbolAttribute(Sym, MCSA_Global);
70 AP.OutStreamer->emitLabel(Sym);
71}
72
73void OcamlGCMetadataPrinter::beginAssembly(Module &M, GCModuleInfo &Info,
74 AsmPrinter &AP) {
75 AP.OutStreamer->switchSection(AP.getObjFileLowering().getTextSection());
76 EmitCamlGlobal(M, AP, "code_begin");
77
78 AP.OutStreamer->switchSection(AP.getObjFileLowering().getDataSection());
79 EmitCamlGlobal(M, AP, "data_begin");
80}
81
82/// emitAssembly - Print the frametable. The ocaml frametable format is thus:
83///
84/// extern "C" struct align(sizeof(intptr_t)) {
85/// uint16_t NumDescriptors;
86/// struct align(sizeof(intptr_t)) {
87/// void *ReturnAddress;
88/// uint16_t FrameSize;
89/// uint16_t NumLiveOffsets;
90/// uint16_t LiveOffsets[NumLiveOffsets];
91/// } Descriptors[NumDescriptors];
92/// } caml${module}__frametable;
93///
94/// Note that this precludes programs from stack frames larger than 64K
95/// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
96/// either condition is detected in a function which uses the GC.
97///
98void OcamlGCMetadataPrinter::finishAssembly(Module &M, GCModuleInfo &Info,
99 AsmPrinter &AP) {
100 unsigned IntPtrSize = M.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 (std::unique_ptr<GCFunctionInfo> &FI :
116 llvm::make_range(Info.funcinfo_begin(), Info.funcinfo_end())) {
117 if (FI->getStrategy().getName() != getStrategy().getName())
118 // this function is managed by some other GC
119 continue;
120 NumDescriptors += FI->size();
121 }
122
123 if (NumDescriptors >= 1 << 16) {
124 // Very rude!
125 report_fatal_error(" Too much descriptor for ocaml GC");
126 }
127 AP.emitInt16(NumDescriptors);
128 AP.emitAlignment(IntPtrSize == 4 ? Align(4) : Align(8));
129
130 for (std::unique_ptr<GCFunctionInfo> &FI :
131 llvm::make_range(Info.funcinfo_begin(), Info.funcinfo_end())) {
132 if (FI->getStrategy().getName() != getStrategy().getName())
133 // this function is managed by some other GC
134 continue;
135
136 uint64_t FrameSize = FI->getFrameSize();
137 if (FrameSize >= 1 << 16) {
138 // Very rude!
139 report_fatal_error("Function '" + FI->getFunction().getName() +
140 "' is too large for the ocaml GC! "
141 "Frame size " +
142 Twine(FrameSize) +
143 ">= 65536.\n"
144 "(" +
145 Twine(reinterpret_cast<uintptr_t>(FI.get())) + ")");
146 }
147
148 AP.OutStreamer->AddComment("live roots for " +
149 Twine(FI->getFunction().getName()));
150 AP.OutStreamer->addBlankLine();
151
152 for (GCFunctionInfo::iterator J = FI->begin(), JE = FI->end(); J != JE;
153 ++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 " +
160 Twine(LiveCount) + " >= 65536.");
161 }
162
163 AP.OutStreamer->emitSymbolValue(J->Label, IntPtrSize);
164 AP.emitInt16(FrameSize);
165 AP.emitInt16(LiveCount);
166
167 for (GCFunctionInfo::live_iterator K = FI->live_begin(J),
168 KE = FI->live_end(J);
169 K != KE; ++K) {
170 if (K->StackOffset >= 1 << 16) {
171 // Very rude!
172 report_fatal_error(
173 "GC root stack offset is outside of fixed stack frame and out "
174 "of range for ocaml GC!");
175 }
176 AP.emitInt16(K->StackOffset);
177 }
178
179 AP.emitAlignment(IntPtrSize == 4 ? Align(4) : Align(8));
180 }
181 }
182}
Analysis containing CSE Info
Definition CSEInfo.cpp:27
Module.h This file contains the declarations for the Module class.
Machine Check Debug Module
static void EmitCamlGlobal(const Module &M, AsmPrinter &AP, const char *Id)
static StringRef getName(Value *V)
This file contains some templates that are useful if you are working with the STL at all.
This file defines the SmallString class.
Y
static TableGen::Emitter::Opt Y("gen-skeleton-entry", EmitSkeleton, "Generate example skeleton entry")
This class is intended to be used as a driving class for all asm writers.
Definition AsmPrinter.h:96
const TargetLoweringObjectFile & getObjFileLowering() const
Return information about object file lowering.
Definition AsmPrinter.cpp:431
void emitAlignment(Align Alignment, const GlobalObject *GV=nullptr, unsigned MaxBytesToEmit=0) const
Emit an alignment directive to the specified power of two boundary.
MCContext & OutContext
This is the context for the output file that we are streaming.
Definition AsmPrinter.h:106
std::unique_ptr< MCStreamer > OutStreamer
This is the MCStreamer object for the file we are generating.
Definition AsmPrinter.h:111
void emitInt16(int Value) const
Emit a short directive and value.
std::vector< GCRoot >::const_iterator live_iterator
Definition GCMetadata.h:84
std::vector< GCPoint >::iterator iterator
Definition GCMetadata.h:82
GCMetadataPrinter - Emits GC metadata as assembly code.
An analysis pass which caches information about the entire Module.
Definition GCMetadata.h:237
LLVM_ABI MCSymbol * getOrCreateSymbol(const Twine &Name)
Lookup the symbol inside with the specified Name.
Definition MCContext.cpp:203
MCSection * getTextSection() const
MCSection * getDataSection() const
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition MCSymbol.h:42
LLVM_ABI void getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV, bool CannotUsePrivateLabel) const
Print the appropriate prefix and the specified global variable's name.
Definition Mangler.cpp:121
A Module instance is used to store all the information related to an LLVM module.
Definition Module.h:67
SmallString - A SmallString is just a SmallVector with methods and accessors that make it work better...
Definition SmallString.h:26
constexpr char Align[]
Key for Kernel::Arg::Metadata::mAlign.
This is an optimization pass for GlobalISel generic memory operations.
Definition AddressRanges.h:18
auto find(R &&Range, const T &Val)
Provide wrappers to std::find which take ranges instead of having to pass begin/end explicitly.
Definition STLExtras.h:1751
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
LLVM_ABI void report_fatal_error(Error Err, bool gen_crash_diag=true)
Definition Error.cpp:167
LLVM_ABI void linkOcamlGCPrinter()
Creates an ocaml-compatible metadata printer.
@ MCSA_Global
.type _foo, @gnu_unique_object
Definition MCDirectives.h:30
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