120 lines
4.1 KiB
C++
120 lines
4.1 KiB
C++
//===- ErlangGCPrinter.cpp - Erlang/OTP frametable emitter ----------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the compiler plugin that is used in order to emit
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// garbage collection information in a convenient layout for parsing and
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// loading in the Erlang/OTP runtime.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/BinaryFormat/ELF.h"
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#include "llvm/CodeGen/AsmPrinter.h"
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#include "llvm/CodeGen/GCMetadata.h"
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#include "llvm/CodeGen/GCMetadataPrinter.h"
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#include "llvm/IR/BuiltinGCs.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Module.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCSectionELF.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Target/TargetLoweringObjectFile.h"
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using namespace llvm;
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namespace {
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class ErlangGCPrinter : public GCMetadataPrinter {
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public:
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void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override;
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};
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} // end anonymous namespace
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static GCMetadataPrinterRegistry::Add<ErlangGCPrinter>
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X("erlang", "erlang-compatible garbage collector");
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void ErlangGCPrinter::finishAssembly(Module &M, GCModuleInfo &Info,
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AsmPrinter &AP) {
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MCStreamer &OS = *AP.OutStreamer;
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unsigned IntPtrSize = M.getDataLayout().getPointerSize();
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// Put this in a custom .note section.
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OS.SwitchSection(
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AP.getObjFileLowering().getContext().getELFSection(".note.gc",
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ELF::SHT_PROGBITS, 0));
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// For each function...
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for (GCModuleInfo::FuncInfoVec::iterator FI = Info.funcinfo_begin(),
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IE = Info.funcinfo_end();
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FI != IE; ++FI) {
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GCFunctionInfo &MD = **FI;
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if (MD.getStrategy().getName() != getStrategy().getName())
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// this function is managed by some other GC
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continue;
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/** A compact GC layout. Emit this data structure:
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*
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* struct {
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* int16_t PointCount;
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* void *SafePointAddress[PointCount];
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* int16_t StackFrameSize; (in words)
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* int16_t StackArity;
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* int16_t LiveCount;
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* int16_t LiveOffsets[LiveCount];
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* } __gcmap_<FUNCTIONNAME>;
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**/
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// Align to address width.
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AP.emitAlignment(IntPtrSize == 4 ? Align(4) : Align(8));
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// Emit PointCount.
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OS.AddComment("safe point count");
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AP.emitInt16(MD.size());
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// And each safe point...
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for (const GCPoint &P : MD) {
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// Emit the address of the safe point.
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OS.AddComment("safe point address");
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MCSymbol *Label = P.Label;
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AP.emitLabelPlusOffset(Label /*Hi*/, 0 /*Offset*/, 4 /*Size*/);
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}
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// Stack information never change in safe points! Only print info from the
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// first call-site.
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GCFunctionInfo::iterator PI = MD.begin();
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// Emit the stack frame size.
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OS.AddComment("stack frame size (in words)");
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AP.emitInt16(MD.getFrameSize() / IntPtrSize);
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// Emit stack arity, i.e. the number of stacked arguments.
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unsigned RegisteredArgs = IntPtrSize == 4 ? 5 : 6;
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unsigned StackArity = MD.getFunction().arg_size() > RegisteredArgs
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? MD.getFunction().arg_size() - RegisteredArgs
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: 0;
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OS.AddComment("stack arity");
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AP.emitInt16(StackArity);
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// Emit the number of live roots in the function.
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OS.AddComment("live root count");
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AP.emitInt16(MD.live_size(PI));
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// And for each live root...
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for (GCFunctionInfo::live_iterator LI = MD.live_begin(PI),
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LE = MD.live_end(PI);
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LI != LE; ++LI) {
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// Emit live root's offset within the stack frame.
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OS.AddComment("stack index (offset / wordsize)");
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AP.emitInt16(LI->StackOffset / IntPtrSize);
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}
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}
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}
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void llvm::linkErlangGCPrinter() {}
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