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//===- OcamlGCPrinter.cpp - Ocaml frametable emitter ----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements printing the assembly code for an Ocaml frametable.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/GCMetadata.h"
#include "llvm/CodeGen/GCMetadataPrinter.h"
#include "llvm/IR/BuiltinGCs.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include <cctype>
#include <cstddef>
#include <cstdint>
#include <string>
using namespace llvm;
namespace {
class OcamlGCMetadataPrinter : public GCMetadataPrinter {
public:
void beginAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override;
void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override;
};
} // end anonymous namespace
static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
Y("ocaml", "ocaml 3.10-compatible collector");
void llvm::linkOcamlGCPrinter() {}
static void EmitCamlGlobal(const Module &M, AsmPrinter &AP, const char *Id) {
const std::string &MId = M.getModuleIdentifier();
std::string SymName;
SymName += "caml";
size_t Letter = SymName.size();
SymName.append(MId.begin(), llvm::find(MId, '.'));
SymName += "__";
SymName += Id;
// Capitalize the first letter of the module name.
SymName[Letter] = toupper(SymName[Letter]);
SmallString<128> TmpStr;
Mangler::getNameWithPrefix(TmpStr, SymName, M.getDataLayout());
MCSymbol *Sym = AP.OutContext.getOrCreateSymbol(TmpStr);
AP.OutStreamer->emitSymbolAttribute(Sym, MCSA_Global);
AP.OutStreamer->emitLabel(Sym);
}
void OcamlGCMetadataPrinter::beginAssembly(Module &M, GCModuleInfo &Info,
AsmPrinter &AP) {
AP.OutStreamer->switchSection(AP.getObjFileLowering().getTextSection());
EmitCamlGlobal(M, AP, "code_begin");
AP.OutStreamer->switchSection(AP.getObjFileLowering().getDataSection());
EmitCamlGlobal(M, AP, "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 GC.
///
void OcamlGCMetadataPrinter::finishAssembly(Module &M, GCModuleInfo &Info,
AsmPrinter &AP) {
unsigned IntPtrSize = M.getDataLayout().getPointerSize();
AP.OutStreamer->switchSection(AP.getObjFileLowering().getTextSection());
EmitCamlGlobal(M, AP, "code_end");
AP.OutStreamer->switchSection(AP.getObjFileLowering().getDataSection());
EmitCamlGlobal(M, AP, "data_end");
// FIXME: Why does ocaml emit this??
AP.OutStreamer->emitIntValue(0, IntPtrSize);
AP.OutStreamer->switchSection(AP.getObjFileLowering().getDataSection());
EmitCamlGlobal(M, AP, "frametable");
int NumDescriptors = 0;
for (std::unique_ptr<GCFunctionInfo> &FI :
llvm::make_range(Info.funcinfo_begin(), Info.funcinfo_end())) {
if (FI->getStrategy().getName() != getStrategy().getName())
// this function is managed by some other GC
continue;
NumDescriptors += FI->size();
}
if (NumDescriptors >= 1 << 16) {
// Very rude!
report_fatal_error(" Too much descriptor for ocaml GC");
}
AP.emitInt16(NumDescriptors);
AP.emitAlignment(IntPtrSize == 4 ? Align(4) : Align(8));
for (std::unique_ptr<GCFunctionInfo> &FI :
llvm::make_range(Info.funcinfo_begin(), Info.funcinfo_end())) {
if (FI->getStrategy().getName() != getStrategy().getName())
// this function is managed by some other GC
continue;
uint64_t FrameSize = FI->getFrameSize();
if (FrameSize >= 1 << 16) {
// Very rude!
report_fatal_error("Function '" + FI->getFunction().getName() +
"' is too large for the ocaml GC! "
"Frame size " +
Twine(FrameSize) +
">= 65536.\n"
"(" +
Twine(reinterpret_cast<uintptr_t>(FI.get())) + ")");
}
AP.OutStreamer->AddComment("live roots for " +
Twine(FI->getFunction().getName()));
AP.OutStreamer->addBlankLine();
for (GCFunctionInfo::iterator J = FI->begin(), JE = FI->end(); J != JE;
++J) {
size_t LiveCount = FI->live_size(J);
if (LiveCount >= 1 << 16) {
// Very rude!
report_fatal_error("Function '" + FI->getFunction().getName() +
"' is too large for the ocaml GC! "
"Live root count " +
Twine(LiveCount) + " >= 65536.");
}
AP.OutStreamer->emitSymbolValue(J->Label, IntPtrSize);
AP.emitInt16(FrameSize);
AP.emitInt16(LiveCount);
for (GCFunctionInfo::live_iterator K = FI->live_begin(J),
KE = FI->live_end(J);
K != KE; ++K) {
if (K->StackOffset >= 1 << 16) {
// Very rude!
report_fatal_error(
"GC root stack offset is outside of fixed stack frame and out "
"of range for ocaml GC!");
}
AP.emitInt16(K->StackOffset);
}
AP.emitAlignment(IntPtrSize == 4 ? Align(4) : Align(8));
}
}
}
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