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clang-p2996/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
Thomas Lively 3f34e1b883 [WebAssembly] Merge used feature sets, update atomics linkage policy 
Summary:
It does not currently make sense to use WebAssembly features in some functions
but not others, so this CL adds an IR pass that takes the union of all used
feature sets and applies it to each function in the module. This allows us to
prevent atomics from being lowered away if some function has opted in to using
them. When atomics is not enabled anywhere, we detect whether there exists any
atomic operations or thread local storage that would be stripped and disallow
linking with objects that contain atomics if and only if atomics or tls are
stripped. When atomics is enabled, mark it as used but do not require it of
other objects in the link. These changes allow libraries that do not use atomics
to be built once and linked into both single-threaded and multithreaded
binaries.

Reviewers: aheejin, sbc100, dschuff

Subscribers: jgravelle-google, hiraditya, sunfish, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59625

llvm-svn: 357226
2019-03-29 00:14:01 +00:00

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//===-- WebAssemblyAsmPrinter.cpp - WebAssembly LLVM assembly writer ------===//
//
// 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file contains a printer that converts from our internal
/// representation of machine-dependent LLVM code to the WebAssembly assembly
/// language.
///
//===----------------------------------------------------------------------===//
#include "WebAssemblyAsmPrinter.h"
#include "InstPrinter/WebAssemblyInstPrinter.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "MCTargetDesc/WebAssemblyTargetStreamer.h"
#include "WebAssembly.h"
#include "WebAssemblyMCInstLower.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblyRegisterInfo.h"
#include "WebAssemblyTargetMachine.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/BinaryFormat/Wasm.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineModuleInfoImpls.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Metadata.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCSymbolWasm.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "asm-printer"
extern cl::opt<bool> WasmKeepRegisters;
//===----------------------------------------------------------------------===//
// Helpers.
//===----------------------------------------------------------------------===//
MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
const TargetRegisterInfo *TRI = Subtarget->getRegisterInfo();
const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64, MVT::v16i8, MVT::v8i16,
MVT::v4i32, MVT::v2i64, MVT::v4f32, MVT::v2f64})
if (TRI->isTypeLegalForClass(*TRC, T))
return T;
LLVM_DEBUG(errs() << "Unknown type for register number: " << RegNo);
llvm_unreachable("Unknown register type");
return MVT::Other;
}
std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
unsigned RegNo = MO.getReg();
assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
"Unlowered physical register encountered during assembly printing");
assert(!MFI->isVRegStackified(RegNo));
unsigned WAReg = MFI->getWAReg(RegNo);
assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
return '$' + utostr(WAReg);
}
WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
return static_cast<WebAssemblyTargetStreamer *>(TS);
}
//===----------------------------------------------------------------------===//
// WebAssemblyAsmPrinter Implementation.
//===----------------------------------------------------------------------===//
void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
for (auto &It : OutContext.getSymbols()) {
// Emit a .globaltype and .eventtype declaration.
auto Sym = cast<MCSymbolWasm>(It.getValue());
if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_GLOBAL)
getTargetStreamer()->emitGlobalType(Sym);
else if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_EVENT)
getTargetStreamer()->emitEventType(Sym);
}
for (const auto &F : M) {
// Emit function type info for all undefined functions
if (F.isDeclarationForLinker() && !F.isIntrinsic()) {
SmallVector<MVT, 4> Results;
SmallVector<MVT, 4> Params;
computeSignatureVTs(F.getFunctionType(), F, TM, Params, Results);
auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
if (!Sym->getSignature()) {
auto Signature = signatureFromMVTs(Results, Params);
Sym->setSignature(Signature.get());
addSignature(std::move(Signature));
}
// FIXME: this was originally intended for post-linking and was only used
// for imports that were only called indirectly (i.e. s2wasm could not
// infer the type from a call). With object files it applies to all
// imports. so fix the names and the tests, or rethink how import
// delcarations work in asm files.
getTargetStreamer()->emitFunctionType(Sym);
if (TM.getTargetTriple().isOSBinFormatWasm() &&
F.hasFnAttribute("wasm-import-module")) {
StringRef Name =
F.getFnAttribute("wasm-import-module").getValueAsString();
Sym->setImportModule(Name);
getTargetStreamer()->emitImportModule(Sym, Name);
}
if (TM.getTargetTriple().isOSBinFormatWasm() &&
F.hasFnAttribute("wasm-import-name")) {
StringRef Name =
F.getFnAttribute("wasm-import-name").getValueAsString();
Sym->setImportName(Name);
getTargetStreamer()->emitImportName(Sym, Name);
}
}
}
for (const auto &G : M.globals()) {
if (!G.hasInitializer() && G.hasExternalLinkage()) {
if (G.getValueType()->isSized()) {
uint16_t Size = M.getDataLayout().getTypeAllocSize(G.getValueType());
OutStreamer->emitELFSize(getSymbol(&G),
MCConstantExpr::create(Size, OutContext));
}
}
}
if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
for (const Metadata *MD : Named->operands()) {
const auto *Tuple = dyn_cast<MDTuple>(MD);
if (!Tuple || Tuple->getNumOperands() != 2)
continue;
const MDString *Name = dyn_cast<MDString>(Tuple->getOperand(0));
const MDString *Contents = dyn_cast<MDString>(Tuple->getOperand(1));
if (!Name || !Contents)
continue;
OutStreamer->PushSection();
std::string SectionName = (".custom_section." + Name->getString()).str();
MCSectionWasm *MySection =
OutContext.getWasmSection(SectionName, SectionKind::getMetadata());
OutStreamer->SwitchSection(MySection);
OutStreamer->EmitBytes(Contents->getString());
OutStreamer->PopSection();
}
}
EmitProducerInfo(M);
EmitTargetFeatures(M);
}
void WebAssemblyAsmPrinter::EmitProducerInfo(Module &M) {
llvm::SmallVector<std::pair<std::string, std::string>, 4> Languages;
if (const NamedMDNode *Debug = M.getNamedMetadata("llvm.dbg.cu")) {
llvm::SmallSet<StringRef, 4> SeenLanguages;
for (size_t I = 0, E = Debug->getNumOperands(); I < E; ++I) {
const auto *CU = cast<DICompileUnit>(Debug->getOperand(I));
StringRef Language = dwarf::LanguageString(CU->getSourceLanguage());
Language.consume_front("DW_LANG_");
if (SeenLanguages.insert(Language).second)
Languages.emplace_back(Language.str(), "");
}
}
llvm::SmallVector<std::pair<std::string, std::string>, 4> Tools;
if (const NamedMDNode *Ident = M.getNamedMetadata("llvm.ident")) {
llvm::SmallSet<StringRef, 4> SeenTools;
for (size_t I = 0, E = Ident->getNumOperands(); I < E; ++I) {
const auto *S = cast<MDString>(Ident->getOperand(I)->getOperand(0));
std::pair<StringRef, StringRef> Field = S->getString().split("version");
StringRef Name = Field.first.trim();
StringRef Version = Field.second.trim();
if (SeenTools.insert(Name).second)
Tools.emplace_back(Name.str(), Version.str());
}
}
int FieldCount = int(!Languages.empty()) + int(!Tools.empty());
if (FieldCount != 0) {
MCSectionWasm *Producers = OutContext.getWasmSection(
".custom_section.producers", SectionKind::getMetadata());
OutStreamer->PushSection();
OutStreamer->SwitchSection(Producers);
OutStreamer->EmitULEB128IntValue(FieldCount);
for (auto &Producers : {std::make_pair("language", &Languages),
std::make_pair("processed-by", &Tools)}) {
if (Producers.second->empty())
continue;
OutStreamer->EmitULEB128IntValue(strlen(Producers.first));
OutStreamer->EmitBytes(Producers.first);
OutStreamer->EmitULEB128IntValue(Producers.second->size());
for (auto &Producer : *Producers.second) {
OutStreamer->EmitULEB128IntValue(Producer.first.size());
OutStreamer->EmitBytes(Producer.first);
OutStreamer->EmitULEB128IntValue(Producer.second.size());
OutStreamer->EmitBytes(Producer.second);
}
}
OutStreamer->PopSection();
}
}
void WebAssemblyAsmPrinter::EmitTargetFeatures(Module &M) {
struct FeatureEntry {
uint8_t Prefix;
StringRef Name;
};
// Read target features and linkage policies from module metadata
SmallVector<FeatureEntry, 4> EmittedFeatures;
for (const SubtargetFeatureKV &KV : WebAssemblyFeatureKV) {
std::string MDKey = (StringRef("wasm-feature-") + KV.Key).str();
Metadata *Policy = M.getModuleFlag(MDKey);
if (Policy == nullptr)
continue;
FeatureEntry Entry;
Entry.Prefix = 0;
Entry.Name = KV.Key;
if (auto *MD = cast<ConstantAsMetadata>(Policy))
if (auto *I = cast<ConstantInt>(MD->getValue()))
Entry.Prefix = I->getZExtValue();
// Silently ignore invalid metadata
if (Entry.Prefix != wasm::WASM_FEATURE_PREFIX_USED &&
Entry.Prefix != wasm::WASM_FEATURE_PREFIX_REQUIRED &&
Entry.Prefix != wasm::WASM_FEATURE_PREFIX_DISALLOWED)
continue;
EmittedFeatures.push_back(Entry);
}
if (EmittedFeatures.size() == 0)
return;
// Emit features and linkage policies into the "target_features" section
MCSectionWasm *FeaturesSection = OutContext.getWasmSection(
".custom_section.target_features", SectionKind::getMetadata());
OutStreamer->PushSection();
OutStreamer->SwitchSection(FeaturesSection);
OutStreamer->EmitULEB128IntValue(EmittedFeatures.size());
for (auto &F : EmittedFeatures) {
OutStreamer->EmitIntValue(F.Prefix, 1);
OutStreamer->EmitULEB128IntValue(F.Name.size());
OutStreamer->EmitBytes(F.Name);
}
OutStreamer->PopSection();
}
void WebAssemblyAsmPrinter::EmitConstantPool() {
assert(MF->getConstantPool()->getConstants().empty() &&
"WebAssembly disables constant pools");
}
void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
// Nothing to do; jump tables are incorporated into the instruction stream.
}
void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
const Function &F = MF->getFunction();
SmallVector<MVT, 1> ResultVTs;
SmallVector<MVT, 4> ParamVTs;
computeSignatureVTs(F.getFunctionType(), F, TM, ParamVTs, ResultVTs);
auto Signature = signatureFromMVTs(ResultVTs, ParamVTs);
auto *WasmSym = cast<MCSymbolWasm>(CurrentFnSym);
WasmSym->setSignature(Signature.get());
addSignature(std::move(Signature));
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
// FIXME: clean up how params and results are emitted (use signatures)
getTargetStreamer()->emitFunctionType(WasmSym);
// Emit the function index.
if (MDNode *Idx = F.getMetadata("wasm.index")) {
assert(Idx->getNumOperands() == 1);
getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
}
SmallVector<wasm::ValType, 16> Locals;
valTypesFromMVTs(MFI->getLocals(), Locals);
getTargetStreamer()->emitLocal(Locals);
AsmPrinter::EmitFunctionBodyStart();
}
void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
LLVM_DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
switch (MI->getOpcode()) {
case WebAssembly::ARGUMENT_i32:
case WebAssembly::ARGUMENT_i32_S:
case WebAssembly::ARGUMENT_i64:
case WebAssembly::ARGUMENT_i64_S:
case WebAssembly::ARGUMENT_f32:
case WebAssembly::ARGUMENT_f32_S:
case WebAssembly::ARGUMENT_f64:
case WebAssembly::ARGUMENT_f64_S:
case WebAssembly::ARGUMENT_v16i8:
case WebAssembly::ARGUMENT_v16i8_S:
case WebAssembly::ARGUMENT_v8i16:
case WebAssembly::ARGUMENT_v8i16_S:
case WebAssembly::ARGUMENT_v4i32:
case WebAssembly::ARGUMENT_v4i32_S:
case WebAssembly::ARGUMENT_v2i64:
case WebAssembly::ARGUMENT_v2i64_S:
case WebAssembly::ARGUMENT_v4f32:
case WebAssembly::ARGUMENT_v4f32_S:
case WebAssembly::ARGUMENT_v2f64:
case WebAssembly::ARGUMENT_v2f64_S:
// These represent values which are live into the function entry, so there's
// no instruction to emit.
break;
case WebAssembly::FALLTHROUGH_RETURN_I32:
case WebAssembly::FALLTHROUGH_RETURN_I32_S:
case WebAssembly::FALLTHROUGH_RETURN_I64:
case WebAssembly::FALLTHROUGH_RETURN_I64_S:
case WebAssembly::FALLTHROUGH_RETURN_F32:
case WebAssembly::FALLTHROUGH_RETURN_F32_S:
case WebAssembly::FALLTHROUGH_RETURN_F64:
case WebAssembly::FALLTHROUGH_RETURN_F64_S:
case WebAssembly::FALLTHROUGH_RETURN_v16i8:
case WebAssembly::FALLTHROUGH_RETURN_v16i8_S:
case WebAssembly::FALLTHROUGH_RETURN_v8i16:
case WebAssembly::FALLTHROUGH_RETURN_v8i16_S:
case WebAssembly::FALLTHROUGH_RETURN_v4i32:
case WebAssembly::FALLTHROUGH_RETURN_v4i32_S:
case WebAssembly::FALLTHROUGH_RETURN_v2i64:
case WebAssembly::FALLTHROUGH_RETURN_v2i64_S:
case WebAssembly::FALLTHROUGH_RETURN_v4f32:
case WebAssembly::FALLTHROUGH_RETURN_v4f32_S:
case WebAssembly::FALLTHROUGH_RETURN_v2f64:
case WebAssembly::FALLTHROUGH_RETURN_v2f64_S: {
// These instructions represent the implicit return at the end of a
// function body. Always pops one value off the stack.
if (isVerbose()) {
OutStreamer->AddComment("fallthrough-return-value");
OutStreamer->AddBlankLine();
}
break;
}
case WebAssembly::FALLTHROUGH_RETURN_VOID:
case WebAssembly::FALLTHROUGH_RETURN_VOID_S:
// This instruction represents the implicit return at the end of a
// function body with no return value.
if (isVerbose()) {
OutStreamer->AddComment("fallthrough-return-void");
OutStreamer->AddBlankLine();
}
break;
case WebAssembly::EXTRACT_EXCEPTION_I32:
case WebAssembly::EXTRACT_EXCEPTION_I32_S:
// These are pseudo instructions that simulates popping values from stack.
// We print these only when we have -wasm-keep-registers on for assembly
// readability.
if (!WasmKeepRegisters)
break;
LLVM_FALLTHROUGH;
default: {
WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
MCInst TmpInst;
MCInstLowering.lower(MI, TmpInst);
EmitToStreamer(*OutStreamer, TmpInst);
break;
}
}
}
bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
unsigned OpNo, unsigned AsmVariant,
const char *ExtraCode,
raw_ostream &OS) {
if (AsmVariant != 0)
report_fatal_error("There are no defined alternate asm variants");
// First try the generic code, which knows about modifiers like 'c' and 'n'.
if (!AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS))
return false;
if (!ExtraCode) {
const MachineOperand &MO = MI->getOperand(OpNo);
switch (MO.getType()) {
case MachineOperand::MO_Immediate:
OS << MO.getImm();
return false;
case MachineOperand::MO_Register:
// FIXME: only opcode that still contains registers, as required by
// MachineInstr::getDebugVariable().
assert(MI->getOpcode() == WebAssembly::INLINEASM);
OS << regToString(MO);
return false;
case MachineOperand::MO_GlobalAddress:
getSymbol(MO.getGlobal())->print(OS, MAI);
printOffset(MO.getOffset(), OS);
return false;
case MachineOperand::MO_ExternalSymbol:
GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
printOffset(MO.getOffset(), OS);
return false;
case MachineOperand::MO_MachineBasicBlock:
MO.getMBB()->getSymbol()->print(OS, MAI);
return false;
default:
break;
}
}
return true;
}
bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
unsigned OpNo,
unsigned AsmVariant,
const char *ExtraCode,
raw_ostream &OS) {
if (AsmVariant != 0)
report_fatal_error("There are no defined alternate asm variants");
// The current approach to inline asm is that "r" constraints are expressed
// as local indices, rather than values on the operand stack. This simplifies
// using "r" as it eliminates the need to push and pop the values in a
// particular order, however it also makes it impossible to have an "m"
// constraint. So we don't support it.
return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
}
// Force static initialization.
extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
}
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