LLVM  4.0.0
ErlangGCPrinter.cpp
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1 //===-- ErlangGCPrinter.cpp - Erlang/OTP frametable emitter -----*- C++ -*-===//
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 the compiler plugin that is used in order to emit
11 // garbage collection information in a convenient layout for parsing and
12 // loading in the Erlang/OTP runtime.
13 //
14 //===----------------------------------------------------------------------===//
15 
18 #include "llvm/CodeGen/GCs.h"
19 #include "llvm/IR/DataLayout.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/Instruction.h"
22 #include "llvm/IR/IntrinsicInst.h"
23 #include "llvm/IR/Metadata.h"
24 #include "llvm/MC/MCAsmInfo.h"
25 #include "llvm/MC/MCContext.h"
26 #include "llvm/MC/MCSectionELF.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSymbol.h"
32 
33 using namespace llvm;
34 
35 namespace {
36 
37 class ErlangGCPrinter : public GCMetadataPrinter {
38 public:
39  void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override;
40 };
41 }
42 
44  X("erlang", "erlang-compatible garbage collector");
45 
47 
48 void ErlangGCPrinter::finishAssembly(Module &M, GCModuleInfo &Info,
49  AsmPrinter &AP) {
50  MCStreamer &OS = *AP.OutStreamer;
51  unsigned IntPtrSize = M.getDataLayout().getPointerSize();
52 
53  // Put this in a custom .note section.
54  OS.SwitchSection(
56  ELF::SHT_PROGBITS, 0));
57 
58  // For each function...
59  for (GCModuleInfo::FuncInfoVec::iterator FI = Info.funcinfo_begin(),
60  IE = Info.funcinfo_end();
61  FI != IE; ++FI) {
62  GCFunctionInfo &MD = **FI;
63  if (MD.getStrategy().getName() != getStrategy().getName())
64  // this function is managed by some other GC
65  continue;
66  /** A compact GC layout. Emit this data structure:
67  *
68  * struct {
69  * int16_t PointCount;
70  * void *SafePointAddress[PointCount];
71  * int16_t StackFrameSize; (in words)
72  * int16_t StackArity;
73  * int16_t LiveCount;
74  * int16_t LiveOffsets[LiveCount];
75  * } __gcmap_<FUNCTIONNAME>;
76  **/
77 
78  // Align to address width.
79  AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
80 
81  // Emit PointCount.
82  OS.AddComment("safe point count");
83  AP.EmitInt16(MD.size());
84 
85  // And each safe point...
86  for (GCFunctionInfo::iterator PI = MD.begin(), PE = MD.end(); PI != PE;
87  ++PI) {
88  // Emit the address of the safe point.
89  OS.AddComment("safe point address");
90  MCSymbol *Label = PI->Label;
91  AP.EmitLabelPlusOffset(Label /*Hi*/, 0 /*Offset*/, 4 /*Size*/);
92  }
93 
94  // Stack information never change in safe points! Only print info from the
95  // first call-site.
97 
98  // Emit the stack frame size.
99  OS.AddComment("stack frame size (in words)");
100  AP.EmitInt16(MD.getFrameSize() / IntPtrSize);
101 
102  // Emit stack arity, i.e. the number of stacked arguments.
103  unsigned RegisteredArgs = IntPtrSize == 4 ? 5 : 6;
104  unsigned StackArity = MD.getFunction().arg_size() > RegisteredArgs
105  ? MD.getFunction().arg_size() - RegisteredArgs
106  : 0;
107  OS.AddComment("stack arity");
108  AP.EmitInt16(StackArity);
109 
110  // Emit the number of live roots in the function.
111  OS.AddComment("live root count");
112  AP.EmitInt16(MD.live_size(PI));
113 
114  // And for each live root...
115  for (GCFunctionInfo::live_iterator LI = MD.live_begin(PI),
116  LE = MD.live_end(PI);
117  LI != LE; ++LI) {
118  // Emit live root's offset within the stack frame.
119  OS.AddComment("stack index (offset / wordsize)");
120  AP.EmitInt16(LI->StackOffset / IntPtrSize);
121  }
122  }
123 }
std::unique_ptr< MCStreamer > OutStreamer
This is the MCStreamer object for the file we are generating.
Definition: AsmPrinter.h:84
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:39
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:52
void EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset, unsigned Size, bool IsSectionRelative=false) const
Emit something like ".long Label+Offset" where the size in bytes of the directive is specified by Siz...
This file contains the declarations for metadata subclasses.
void linkErlangGCPrinter()
Creates an erlang-compatible metadata printer.
size_t arg_size() const
Definition: Function.cpp:327
std::vector< GCPoint >::iterator iterator
Definition: GCMetadata.h:76
An analysis pass which caches information about the entire Module.
Definition: GCMetadata.h:155
virtual void AddComment(const Twine &T, bool EOL=true)
Add a textual comment.
Definition: MCStreamer.h:269
const std::string & getName() const
Return the name of the GC strategy.
Definition: GCStrategy.h:101
void EmitInt16(int Value) const
Emit a short directive and value.
Streaming machine code generation interface.
Definition: MCStreamer.h:161
virtual void SwitchSection(MCSection *Section, const MCExpr *Subsection=nullptr)
Set the current section where code is being emitted to Section.
Definition: MCStreamer.cpp:829
GCStrategy & getStrategy()
getStrategy - Return the GC strategy for the function.
Definition: GCMetadata.h:107
This class is intended to be used as a driving class for all asm writers.
Definition: AsmPrinter.h:67
uint64_t getFrameSize() const
getFrameSize/setFrameSize - Records the function's frame size.
Definition: GCMetadata.h:130
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang","erlang-compatible garbage collector")
FuncInfoVec::iterator funcinfo_begin()
Definition: GCMetadata.h:171
size_t live_size(const iterator &p) const
Definition: GCMetadata.h:149
void EmitAlignment(unsigned NumBits, const GlobalObject *GO=nullptr) const
Emit an alignment directive to the specified power of two boundary.
live_iterator live_begin(const iterator &p)
live_begin/live_end - Iterators for live roots at a given safe point.
Definition: GCMetadata.h:147
FuncInfoVec::iterator funcinfo_end()
Definition: GCMetadata.h:172
iterator begin()
begin/end - Iterators for safe points.
Definition: GCMetadata.h:135
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.cpp:384
size_t size() const
Definition: GCMetadata.h:137
const TargetLoweringObjectFile & getObjFileLowering() const
Return information about object file lowering.
Definition: AsmPrinter.cpp:144
MCSectionELF * getELFSection(const Twine &Section, unsigned Type, unsigned Flags)
Definition: MCContext.h:341
const Function & getFunction() const
getFunction - Return the function to which this metadata applies.
Definition: GCMetadata.h:103
GCMetadataPrinter - Emits GC metadata as assembly code.
live_iterator live_end(const iterator &p)
Definition: GCMetadata.h:148
Garbage collection metadata for a single function.
Definition: GCMetadata.h:74
unsigned getPointerSize(unsigned AS=0) const
Layout pointer size FIXME: The defaults need to be removed once all of the backends/clients are updat...
Definition: DataLayout.cpp:608
std::vector< GCRoot >::const_iterator live_iterator
Definition: GCMetadata.h:78
A static registration template.
Definition: Registry.h:115