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llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
Derek Schuff 7f409cd82b
[Object][Wasm] Allow parsing of GC types in type and table sections (#79235) 
This change allows a WasmObjectFile to be created from a wasm file even 
if it uses typed funcrefs and GC types. It does not significantly change how 
lib/Object models its various internal types (e.g. WasmSignature,
WasmElemSegment), so LLVM does not really "support" or understand such
files, but it is sufficient to parse the type, global and element sections, discarding
types that are not understood. This is useful for low-level binary tools such as
nm and objcopy, which use only limited aspects of the binary (such as function
definitions) or deal with sections as opaque blobs.

This is done by allowing `WasmValType` to have a value of `OTHERREF`
(representing any unmodeled reference type), and adding a field to
`WasmSignature` indicating it's a placeholder for an unmodeled reference 
type (since there is a 1:1 correspondence between WasmSignature objects
and types in the type section).
Then the object file parsers for the type and element sections are expanded
to parse encoded reference types and discard any unmodeled fields.
2024-01-25 09:48:38 -08:00

752 lines
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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 "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "MCTargetDesc/WebAssemblyTargetStreamer.h"
#include "TargetInfo/WebAssemblyTargetInfo.h"
#include "Utils/WebAssemblyTypeUtilities.h"
#include "WebAssembly.h"
#include "WebAssemblyMCInstLower.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblyRegisterInfo.h"
#include "WebAssemblyRuntimeLibcallSignatures.h"
#include "WebAssemblyTargetMachine.h"
#include "WebAssemblyUtilities.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/ValueTracking.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/MC/TargetRegistry.h"
#include "llvm/Support/Debug.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) {
Register RegNo = MO.getReg();
assert(RegNo.isVirtual() &&
"Unlowered physical register encountered during assembly printing");
assert(!MFI->isVRegStackified(RegNo));
unsigned WAReg = MFI->getWAReg(RegNo);
assert(WAReg != WebAssembly::UnusedReg);
return '$' + utostr(WAReg);
}
WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
return static_cast<WebAssemblyTargetStreamer *>(TS);
}
// Emscripten exception handling helpers
//
// This converts invoke names generated by LowerEmscriptenEHSjLj to real names
// that are expected by JavaScript glue code. The invoke names generated by
// Emscripten JS glue code are based on their argument and return types; for
// example, for a function that takes an i32 and returns nothing, it is
// 'invoke_vi'. But the format of invoke generated by LowerEmscriptenEHSjLj pass
// contains a mangled string generated from their IR types, for example,
// "__invoke_void_%struct.mystruct*_int", because final wasm types are not
// available in the IR pass. So we convert those names to the form that
// Emscripten JS code expects.
//
// Refer to LowerEmscriptenEHSjLj pass for more details.
// Returns true if the given function name is an invoke name generated by
// LowerEmscriptenEHSjLj pass.
static bool isEmscriptenInvokeName(StringRef Name) {
if (Name.front() == '"' && Name.back() == '"')
Name = Name.substr(1, Name.size() - 2);
return Name.starts_with("__invoke_");
}
// Returns a character that represents the given wasm value type in invoke
// signatures.
static char getInvokeSig(wasm::ValType VT) {
switch (VT) {
case wasm::ValType::I32:
return 'i';
case wasm::ValType::I64:
return 'j';
case wasm::ValType::F32:
return 'f';
case wasm::ValType::F64:
return 'd';
case wasm::ValType::V128:
return 'V';
case wasm::ValType::FUNCREF:
return 'F';
case wasm::ValType::EXTERNREF:
return 'X';
default:
llvm_unreachable("Unhandled wasm::ValType enum");
}
}
// Given the wasm signature, generate the invoke name in the format JS glue code
// expects.
static std::string getEmscriptenInvokeSymbolName(wasm::WasmSignature *Sig) {
assert(Sig->Returns.size() <= 1);
std::string Ret = "invoke_";
if (!Sig->Returns.empty())
for (auto VT : Sig->Returns)
Ret += getInvokeSig(VT);
else
Ret += 'v';
// Invokes' first argument is a pointer to the original function, so skip it
for (unsigned I = 1, E = Sig->Params.size(); I < E; I++)
Ret += getInvokeSig(Sig->Params[I]);
return Ret;
}
//===----------------------------------------------------------------------===//
// WebAssemblyAsmPrinter Implementation.
//===----------------------------------------------------------------------===//
MCSymbolWasm *WebAssemblyAsmPrinter::getMCSymbolForFunction(
const Function *F, bool EnableEmEH, wasm::WasmSignature *Sig,
bool &InvokeDetected) {
MCSymbolWasm *WasmSym = nullptr;
if (EnableEmEH && isEmscriptenInvokeName(F->getName())) {
assert(Sig);
InvokeDetected = true;
if (Sig->Returns.size() > 1) {
std::string Msg =
"Emscripten EH/SjLj does not support multivalue returns: " +
std::string(F->getName()) + ": " +
WebAssembly::signatureToString(Sig);
report_fatal_error(Twine(Msg));
}
WasmSym = cast<MCSymbolWasm>(
GetExternalSymbolSymbol(getEmscriptenInvokeSymbolName(Sig)));
} else {
WasmSym = cast<MCSymbolWasm>(getSymbol(F));
}
return WasmSym;
}
void WebAssemblyAsmPrinter::emitGlobalVariable(const GlobalVariable *GV) {
if (!WebAssembly::isWasmVarAddressSpace(GV->getAddressSpace())) {
AsmPrinter::emitGlobalVariable(GV);
return;
}
assert(!GV->isThreadLocal());
MCSymbolWasm *Sym = cast<MCSymbolWasm>(getSymbol(GV));
if (!Sym->getType()) {
SmallVector<MVT, 1> VTs;
Type *GlobalVT = GV->getValueType();
if (Subtarget) {
// Subtarget is only set when a function is defined, because
// each function can declare a different subtarget. For example,
// on ARM a compilation unit might have a function on ARM and
// another on Thumb. Therefore only if Subtarget is non-null we
// can actually calculate the legal VTs.
const WebAssemblyTargetLowering &TLI = *Subtarget->getTargetLowering();
computeLegalValueVTs(TLI, GV->getParent()->getContext(),
GV->getParent()->getDataLayout(), GlobalVT, VTs);
}
WebAssembly::wasmSymbolSetType(Sym, GlobalVT, VTs);
}
emitVisibility(Sym, GV->getVisibility(), !GV->isDeclaration());
emitSymbolType(Sym);
if (GV->hasInitializer()) {
assert(getSymbolPreferLocal(*GV) == Sym);
emitLinkage(GV, Sym);
OutStreamer->emitLabel(Sym);
// TODO: Actually emit the initializer value. Otherwise the global has the
// default value for its type (0, ref.null, etc).
OutStreamer->addBlankLine();
}
}
MCSymbol *WebAssemblyAsmPrinter::getOrCreateWasmSymbol(StringRef Name) {
auto *WasmSym = cast<MCSymbolWasm>(GetExternalSymbolSymbol(Name));
// May be called multiple times, so early out.
if (WasmSym->getType())
return WasmSym;
const WebAssemblySubtarget &Subtarget = getSubtarget();
// Except for certain known symbols, all symbols used by CodeGen are
// functions. It's OK to hardcode knowledge of specific symbols here; this
// method is precisely there for fetching the signatures of known
// Clang-provided symbols.
if (Name == "__stack_pointer" || Name == "__tls_base" ||
Name == "__memory_base" || Name == "__table_base" ||
Name == "__tls_size" || Name == "__tls_align") {
bool Mutable =
Name == "__stack_pointer" || Name == "__tls_base";
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
WasmSym->setGlobalType(wasm::WasmGlobalType{
uint8_t(Subtarget.hasAddr64() ? wasm::WASM_TYPE_I64
: wasm::WASM_TYPE_I32),
Mutable});
return WasmSym;
}
if (Name.starts_with("GCC_except_table")) {
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_DATA);
return WasmSym;
}
SmallVector<wasm::ValType, 4> Returns;
SmallVector<wasm::ValType, 4> Params;
if (Name == "__cpp_exception" || Name == "__c_longjmp") {
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_TAG);
// In static linking we define tag symbols in WasmException::endModule().
// But we may have multiple objects to be linked together, each of which
// defines the tag symbols. To resolve them, we declare them as weak. In
// dynamic linking we make tag symbols undefined in the backend, define it
// in JS, and feed them to each importing module.
if (!isPositionIndependent())
WasmSym->setWeak(true);
WasmSym->setExternal(true);
// Currently both C++ exceptions and C longjmps have a single pointer type
// param. For C++ exceptions it is a pointer to an exception object, and for
// C longjmps it is pointer to a struct that contains a setjmp buffer and a
// longjmp return value. We may consider using multiple value parameters for
// longjmps later when multivalue support is ready.
wasm::ValType AddrType =
Subtarget.hasAddr64() ? wasm::ValType::I64 : wasm::ValType::I32;
Params.push_back(AddrType);
} else { // Function symbols
WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
getLibcallSignature(Subtarget, Name, Returns, Params);
}
auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
std::move(Params));
WasmSym->setSignature(Signature.get());
addSignature(std::move(Signature));
return WasmSym;
}
void WebAssemblyAsmPrinter::emitSymbolType(const MCSymbolWasm *Sym) {
std::optional<wasm::WasmSymbolType> WasmTy = Sym->getType();
if (!WasmTy)
return;
switch (*WasmTy) {
case wasm::WASM_SYMBOL_TYPE_GLOBAL:
getTargetStreamer()->emitGlobalType(Sym);
break;
case wasm::WASM_SYMBOL_TYPE_TAG:
getTargetStreamer()->emitTagType(Sym);
break;
case wasm::WASM_SYMBOL_TYPE_TABLE:
getTargetStreamer()->emitTableType(Sym);
break;
default:
break; // We only handle globals, tags and tables here
}
}
void WebAssemblyAsmPrinter::emitDecls(const Module &M) {
if (signaturesEmitted)
return;
signaturesEmitted = true;
// Normally symbols for globals get discovered as the MI gets lowered,
// but we need to know about them ahead of time. This will however,
// only find symbols that have been used. Unused symbols from globals will
// not be found here.
MachineModuleInfoWasm &MMIW = MMI->getObjFileInfo<MachineModuleInfoWasm>();
for (StringRef Name : MMIW.MachineSymbolsUsed) {
auto *WasmSym = cast<MCSymbolWasm>(getOrCreateWasmSymbol(Name));
if (WasmSym->isFunction()) {
// TODO(wvo): is there any case where this overlaps with the call to
// emitFunctionType in the loop below?
getTargetStreamer()->emitFunctionType(WasmSym);
}
}
for (auto &It : OutContext.getSymbols()) {
// Emit .globaltype, .tagtype, or .tabletype declarations for extern
// declarations, i.e. those that have only been declared (but not defined)
// in the current module
auto Sym = cast<MCSymbolWasm>(It.getValue());
if (!Sym->isDefined())
emitSymbolType(Sym);
}
DenseSet<MCSymbol *> InvokeSymbols;
for (const auto &F : M) {
if (F.isIntrinsic())
continue;
// Emit function type info for all functions. This will emit duplicate
// information for defined functions (which already have function type
// info emitted alongside their definition), but this is necessary in
// order to enable the single-pass WebAssemblyAsmTypeCheck to succeed.
SmallVector<MVT, 4> Results;
SmallVector<MVT, 4> Params;
computeSignatureVTs(F.getFunctionType(), &F, F, TM, Params, Results);
// At this point these MCSymbols may or may not have been created already
// and thus also contain a signature, but we need to get the signature
// anyway here in case it is an invoke that has not yet been created. We
// will discard it later if it turns out not to be necessary.
auto Signature = signatureFromMVTs(Results, Params);
bool InvokeDetected = false;
auto *Sym = getMCSymbolForFunction(
&F, WebAssembly::WasmEnableEmEH || WebAssembly::WasmEnableEmSjLj,
Signature.get(), InvokeDetected);
// Multiple functions can be mapped to the same invoke symbol. For
// example, two IR functions '__invoke_void_i8*' and '__invoke_void_i32'
// are both mapped to '__invoke_vi'. We keep them in a set once we emit an
// Emscripten EH symbol so we don't emit the same symbol twice.
if (InvokeDetected && !InvokeSymbols.insert(Sym).second)
continue;
Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
if (!Sym->getSignature()) {
Sym->setSignature(Signature.get());
addSignature(std::move(Signature));
} else {
// This symbol has already been created and had a signature. Discard it.
Signature.reset();
}
getTargetStreamer()->emitFunctionType(Sym);
if (F.hasFnAttribute("wasm-import-module")) {
StringRef Name =
F.getFnAttribute("wasm-import-module").getValueAsString();
Sym->setImportModule(storeName(Name));
getTargetStreamer()->emitImportModule(Sym, Name);
}
if (F.hasFnAttribute("wasm-import-name")) {
// If this is a converted Emscripten EH/SjLj symbol, we shouldn't use
// the original function name but the converted symbol name.
StringRef Name =
InvokeDetected
? Sym->getName()
: F.getFnAttribute("wasm-import-name").getValueAsString();
Sym->setImportName(storeName(Name));
getTargetStreamer()->emitImportName(Sym, Name);
}
if (F.hasFnAttribute("wasm-export-name")) {
auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
StringRef Name = F.getFnAttribute("wasm-export-name").getValueAsString();
Sym->setExportName(storeName(Name));
getTargetStreamer()->emitExportName(Sym, Name);
}
}
}
void WebAssemblyAsmPrinter::emitEndOfAsmFile(Module &M) {
// This is required to emit external declarations (like .functypes) when
// no functions are defined in the compilation unit and therefore,
// emitDecls() is not called until now.
emitDecls(M);
// When a function's address is taken, a TABLE_INDEX relocation is emitted
// against the function symbol at the use site. However the relocation
// doesn't explicitly refer to the table. In the future we may want to
// define a new kind of reloc against both the function and the table, so
// that the linker can see that the function symbol keeps the table alive,
// but for now manually mark the table as live.
for (const auto &F : M) {
if (!F.isIntrinsic() && F.hasAddressTaken()) {
MCSymbolWasm *FunctionTable =
WebAssembly::getOrCreateFunctionTableSymbol(OutContext, Subtarget);
OutStreamer->emitSymbolAttribute(FunctionTable, MCSA_NoDeadStrip);
break;
}
}
for (const auto &G : M.globals()) {
if (!G.hasInitializer() && G.hasExternalLinkage() &&
!WebAssembly::isWasmVarAddressSpace(G.getAddressSpace()) &&
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);
EmitFunctionAttributes(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;
std::string Name;
};
// Read target features and linkage policies from module metadata
SmallVector<FeatureEntry, 4> EmittedFeatures;
auto EmitFeature = [&](std::string Feature) {
std::string MDKey = (StringRef("wasm-feature-") + Feature).str();
Metadata *Policy = M.getModuleFlag(MDKey);
if (Policy == nullptr)
return;
FeatureEntry Entry;
Entry.Prefix = 0;
Entry.Name = Feature;
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)
return;
EmittedFeatures.push_back(Entry);
};
for (const SubtargetFeatureKV &KV : WebAssemblyFeatureKV) {
EmitFeature(KV.Key);
}
// This pseudo-feature tells the linker whether shared memory would be safe
EmitFeature("shared-mem");
// This is an "architecture", not a "feature", but we emit it as such for
// the benefit of tools like Binaryen and consistency with other producers.
// FIXME: Subtarget is null here, so can't Subtarget->hasAddr64() ?
if (M.getDataLayout().getPointerSize() == 8) {
// Can't use EmitFeature since "wasm-feature-memory64" is not a module
// flag.
EmittedFeatures.push_back({wasm::WASM_FEATURE_PREFIX_USED, "memory64"});
}
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::EmitFunctionAttributes(Module &M) {
auto V = M.getNamedGlobal("llvm.global.annotations");
if (!V)
return;
// Group all the custom attributes by name.
MapVector<StringRef, SmallVector<MCSymbol *, 4>> CustomSections;
const ConstantArray *CA = cast<ConstantArray>(V->getOperand(0));
for (Value *Op : CA->operands()) {
auto *CS = cast<ConstantStruct>(Op);
// The first field is a pointer to the annotated variable.
Value *AnnotatedVar = CS->getOperand(0)->stripPointerCasts();
// Only annotated functions are supported for now.
if (!isa<Function>(AnnotatedVar))
continue;
auto *F = cast<Function>(AnnotatedVar);
// The second field is a pointer to a global annotation string.
auto *GV = cast<GlobalVariable>(CS->getOperand(1)->stripPointerCasts());
StringRef AnnotationString;
getConstantStringInfo(GV, AnnotationString);
auto *Sym = cast<MCSymbolWasm>(getSymbol(F));
CustomSections[AnnotationString].push_back(Sym);
}
// Emit a custom section for each unique attribute.
for (const auto &[Name, Symbols] : CustomSections) {
MCSectionWasm *CustomSection = OutContext.getWasmSection(
".custom_section.llvm.func_attr.annotate." + Name, SectionKind::getMetadata());
OutStreamer->pushSection();
OutStreamer->switchSection(CustomSection);
for (auto &Sym : Symbols) {
OutStreamer->emitValue(
MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_WASM_FUNCINDEX,
OutContext),
4);
}
OutStreamer->popSection();
}
}
void WebAssemblyAsmPrinter::emitConstantPool() {
emitDecls(*MMI->getModule());
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, 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);
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');
WebAssembly_MC::verifyInstructionPredicates(MI->getOpcode(),
Subtarget->getFeatureBits());
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: {
// These instructions represent the implicit return at the end of a
// function body.
if (isVerbose()) {
OutStreamer->AddComment("fallthrough-return");
OutStreamer->addBlankLine();
}
break;
}
case WebAssembly::COMPILER_FENCE:
// This is a compiler barrier that prevents instruction reordering during
// backend compilation, and should not be emitted.
break;
default: {
WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
MCInst TmpInst;
MCInstLowering.lower(MI, TmpInst);
EmitToStreamer(*OutStreamer, TmpInst);
break;
}
}
}
bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
unsigned OpNo,
const char *ExtraCode,
raw_ostream &OS) {
// First try the generic code, which knows about modifiers like 'c' and 'n'.
if (!AsmPrinter::PrintAsmOperand(MI, OpNo, 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:
PrintSymbolOperand(MO, 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,
const char *ExtraCode,
raw_ostream &OS) {
// 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, ExtraCode, OS);
}
// Force static initialization.
extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmPrinter() {
RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
}
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