[WebAssembly] Added a .globaltype directive to .s output.

[aardappel]

Summary

Assembly output can use globals like __stack_pointer implicitly,
but has no way of indicating the type of such a global, which makes
it hard for tools processing it (such as the MC Assembler) to
reconstruct this information.

The improved assembler directives parsing (in progress in
https://reviews.llvm.org/D53842) will make use of this information.

Also deleted code for the .import_global directive which was unused.

New test case in userstack.ll

[dschuff]

lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h

46

update comment.

[sbc100]

Nice!

lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

87

I like newline between these top loops, but perhaps thats just a personal preference.

[aardappel]

Code review fixes.

[aheejin]

Is the parsing side of this .globaltype directive is going to be added separately, or is it already being handled?

[aardappel]

In D54012#1285855, @aheejin wrote:

Is the parsing side of this .globaltype directive is going to be added separately, or is it already being handled?

It is being added here: https://reviews.llvm.org/D53842

lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h

public:
   /// .local
   virtual void emitLocal(ArrayRef<MVT> Types) = 0;
   /// .endfunc
   virtual void emitEndFunc() = 0;
   /// .functype
   virtual void emitIndirectFunctionType(MCSymbolWasm *Symbol) = 0;
   /// .indidx
   virtual void emitIndIdx(const MCExpr *Value) = 0;
   /// .import_global
-  virtual void emitGlobalImport(StringRef name) = 0;
+  virtual void emitGlobalType(MCSymbolWasm *Sym) = 0;
   /// .import_module
   virtual void emitImportModule(MCSymbolWasm *Sym, StringRef ModuleName) = 0;
 
 protected:
   void emitValueType(wasm::ValType Type);
 };
 
 /// This part is for ascii assembly output
 class WebAssemblyTargetAsmStreamer final : public WebAssemblyTargetStreamer {
   formatted_raw_ostream &OS;
 
 public:
   WebAssemblyTargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
 
   void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(MCSymbolWasm *Symbol) override;
   void emitIndIdx(const MCExpr *Value) override;
-  void emitGlobalImport(StringRef name) override;
+  void emitGlobalType(MCSymbolWasm *Sym) override;
   void emitImportModule(MCSymbolWasm *Sym, StringRef ModuleName) override;
 };
 
 /// This part is for Wasm object output
 class WebAssemblyTargetWasmStreamer final : public WebAssemblyTargetStreamer {
 public:
   explicit WebAssemblyTargetWasmStreamer(MCStreamer &S);
 
   void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(MCSymbolWasm *Symbol) override;
   void emitIndIdx(const MCExpr *Value) override;
-  void emitGlobalImport(StringRef name) override;
+  void emitGlobalType(MCSymbolWasm *Sym) override;
   void emitImportModule(MCSymbolWasm *Sym, StringRef ModuleName) override;
 };
 
 } // end namespace llvm
 
 #endif

lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp

else {
     OS << ", "
        << WebAssembly::TypeToString(Symbol->getSignature()->Returns.front());
   }
   for (auto Ty : Symbol->getSignature()->Params)
     OS << ", " << WebAssembly::TypeToString(Ty);
   OS << '\n';
 }
 
-void WebAssemblyTargetAsmStreamer::emitGlobalImport(StringRef name) {
-  OS << "\t.import_global\t" << name << '\n';
+void WebAssemblyTargetAsmStreamer::emitGlobalType(MCSymbolWasm *Sym) {
+  OS << "\t.globaltype\t" << Sym->getName() << ", " <<
+        WebAssembly::TypeToString(
+          static_cast<wasm::ValType>(Sym->getGlobalType().Type)) <<
+        '\n';
 }
 
 void WebAssemblyTargetAsmStreamer::emitImportModule(MCSymbolWasm *Sym,
                                                     StringRef ModuleName) {
   OS << "\t.import_module\t" << Sym->getName() << ", " << ModuleName << '\n';
 }
 
 void WebAssemblyTargetAsmStreamer::emitIndIdx(const MCExpr *Value) {

 }
 
 void WebAssemblyTargetWasmStreamer::emitIndirectFunctionType(
     MCSymbolWasm *Symbol) {
   // Symbol already has its arguments and result set.
   Symbol->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
 }
 
-void WebAssemblyTargetWasmStreamer::emitGlobalImport(StringRef name) {
-  llvm_unreachable(".global_import is not needed for direct wasm output");
+void WebAssemblyTargetWasmStreamer::emitGlobalType(MCSymbolWasm *Sym) {
+  // Not needed.
 }
 
 void WebAssemblyTargetWasmStreamer::emitImportModule(MCSymbolWasm *Sym,
                                                      StringRef ModuleName) {
   Sym->setModuleName(ModuleName);
 }

lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
   return static_cast<WebAssemblyTargetStreamer *>(TS);
 }
 
 //===----------------------------------------------------------------------===//
 // WebAssemblyAsmPrinter Implementation.
 //===----------------------------------------------------------------------===//
 
 void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
+  for (auto &It : OutContext.getSymbols()) {
+    // Emit a .globaltype declaration.
+    auto Sym = cast<MCSymbolWasm>(It.getValue());
+    if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_GLOBAL) {
+      getTargetStreamer()->emitGlobalType(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));
       if (!Sym->getSignature()) {
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 MDTuple *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)

test/CodeGen/WebAssembly/userstack.ll

 ; CHECK-NEXT:  # %{{[0-9]+}}{{$}}
 ; CHECK-NEXT:  #NO_APP
 define void @inline_asm() {
   %tmp = alloca i8
   call void asm sideeffect "# %0", "r"(i8* %tmp)
   ret void
 }
 
+; CHECK: .globaltype  __stack_pointer, i32{{$}}
+
 ; TODO: test over-aligned alloca