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//===-- OcamlCollector.cpp - Ocaml frametable emitter ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements lowering for the llvm.gc* intrinsics compatible with
// Objective Caml 3.10.0, which uses a liveness-accurate static stack map.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GCs.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/GCStrategy.h"
#include "llvm/Module.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
namespace {
class VISIBILITY_HIDDEN OcamlGCMetadataPrinter : public GCMetadataPrinter {
public:
void beginAssembly(std::ostream &OS, AsmPrinter &AP,
const TargetAsmInfo &TAI);
void finishAssembly(std::ostream &OS, AsmPrinter &AP,
const TargetAsmInfo &TAI);
};
}
static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
Y("ocaml", "ocaml 3.10-compatible collector");
GCMetadataPrinter *llvm::createOcamlMetadataPrinter() {
return new OcamlGCMetadataPrinter();
}
static void EmitCamlGlobal(const Module &M, std::ostream &OS, AsmPrinter &AP,
const TargetAsmInfo &TAI, const char *Id) {
const std::string &MId = M.getModuleIdentifier();
std::string Mangled;
Mangled += TAI.getGlobalPrefix();
Mangled += "caml";
size_t Letter = Mangled.size();
Mangled.append(MId.begin(), std::find(MId.begin(), MId.end(), '.'));
Mangled += "__";
Mangled += Id;
// Capitalize the first letter of the module name.
Mangled[Letter] = toupper(Mangled[Letter]);
if (const char *GlobalDirective = TAI.getGlobalDirective())
OS << GlobalDirective << Mangled << "\n";
OS << Mangled << ":\n";
}
void OcamlGCMetadataPrinter::beginAssembly(std::ostream &OS, AsmPrinter &AP,
const TargetAsmInfo &TAI) {
AP.SwitchToTextSection(TAI.getTextSection());
EmitCamlGlobal(getModule(), OS, AP, TAI, "code_begin");
AP.SwitchToDataSection(TAI.getDataSection());
EmitCamlGlobal(getModule(), OS, AP, TAI, "data_begin");
}
/// emitAssembly - Print the frametable. The ocaml frametable format is thus:
///
/// extern "C" struct align(sizeof(intptr_t)) {
/// uint16_t NumDescriptors;
/// struct align(sizeof(intptr_t)) {
/// void *ReturnAddress;
/// uint16_t FrameSize;
/// uint16_t NumLiveOffsets;
/// uint16_t LiveOffsets[NumLiveOffsets];
/// } Descriptors[NumDescriptors];
/// } caml${module}__frametable;
///
/// Note that this precludes programs from stack frames larger than 64K
/// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
/// either condition is detected in a function which uses the collector.
///
void OcamlGCMetadataPrinter::finishAssembly(std::ostream &OS, AsmPrinter &AP,
const TargetAsmInfo &TAI) {
const char *AddressDirective;
int AddressAlignLog;
if (AP.TM.getTargetData()->getPointerSize() == sizeof(int32_t)) {
AddressDirective = TAI.getData32bitsDirective();
AddressAlignLog = 2;
} else {
AddressDirective = TAI.getData64bitsDirective();
AddressAlignLog = 3;
}
AP.SwitchToTextSection(TAI.getTextSection());
EmitCamlGlobal(getModule(), OS, AP, TAI, "code_end");
AP.SwitchToDataSection(TAI.getDataSection());
EmitCamlGlobal(getModule(), OS, AP, TAI, "data_end");
OS << AddressDirective << 0; // FIXME: Why does ocaml emit this??
AP.EOL();
AP.SwitchToDataSection(TAI.getDataSection());
EmitCamlGlobal(getModule(), OS, AP, TAI, "frametable");
for (iterator FI = begin(), FE = end(); FI != FE; ++FI) {
CollectorMetadata &MD = **FI;
OS << "\t" << TAI.getCommentString() << " live roots for "
<< MD.getFunction().getNameStart() << "\n";
for (CollectorMetadata::iterator PI = MD.begin(),
PE = MD.end(); PI != PE; ++PI) {
uint64_t FrameSize = MD.getFrameSize();
if (FrameSize >= 1<<16) {
cerr << "Function '" << MD.getFunction().getNameStart()
<< "' is too large for the ocaml collector! "
<< "Frame size " << FrameSize << " >= 65536.\n";
abort(); // Very rude!
}
size_t LiveCount = MD.live_size(PI);
if (LiveCount >= 1<<16) {
cerr << "Function '" << MD.getFunction().getNameStart()
<< "' is too large for the ocaml collector! "
<< "Live root count " << LiveCount << " >= 65536.\n";
abort(); // Very rude!
}
OS << AddressDirective
<< TAI.getPrivateGlobalPrefix() << "label" << PI->Num;
AP.EOL("call return address");
AP.EmitInt16(FrameSize);
AP.EOL("stack frame size");
AP.EmitInt16(LiveCount);
AP.EOL("live root count");
for (CollectorMetadata::live_iterator LI = MD.live_begin(PI),
LE = MD.live_end(PI);
LI != LE; ++LI) {
assert(LI->StackOffset < 1<<16 &&
"GC root stack offset is outside of fixed stack frame and out "
"of range for Ocaml collector!");
OS << "\t.word\t" << LI->StackOffset;
AP.EOL("stack offset");
}
AP.EmitAlignment(AddressAlignLog);
}
}
}
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