[PATCH] D54012: [WebAssembly] Added a .globaltype directive to .s output.

[Wouter van Oortmerssen via Phabricator via llvm-commits]

aardappel created this revision.
aardappel added reviewers: dschuff, sbc100.
Herald added subscribers: llvm-commits, sunfish, aheejin, jgravelle-google.

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


Repository:
  rL LLVM

https://reviews.llvm.org/D54012

Files:
  lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
  lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
  lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
  test/CodeGen/WebAssembly/userstack.ll


Index: test/CodeGen/WebAssembly/userstack.ll
===================================================================
--- test/CodeGen/WebAssembly/userstack.ll
+++ test/CodeGen/WebAssembly/userstack.ll
@@ -330,4 +330,6 @@
   ret void
 }
 
+; CHECK: .globaltype	__stack_pointer, i32{{$}}
+
 ; TODO: test over-aligned alloca
Index: lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
===================================================================
--- lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
+++ lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
@@ -78,6 +78,13 @@
 //===----------------------------------------------------------------------===//
 
 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()) {
@@ -114,7 +121,6 @@
       }
     }
   }
-
   if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
     for (const Metadata *MD : Named->operands()) {
       const MDTuple *Tuple = dyn_cast<MDTuple>(MD);
Index: lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
===================================================================
--- lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
+++ lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
@@ -44,7 +44,7 @@
   /// .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;
 
@@ -65,7 +65,7 @@
   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;
 };
 
@@ -80,7 +80,7 @@
   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;
 };
 
Index: lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
===================================================================
--- lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
+++ lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
@@ -99,8 +99,11 @@
   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,
@@ -152,8 +155,8 @@
   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,


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