[WebAssembly] Simplify generation of "names" section

Simplify generation of "names" section by simply iterating
over the DefinedFunctions array.

This even fixes some bugs, judging by the test changes required.
Some tests are asserting that functions are named multiple times,
other tests are asserting that the "names" section contains the
function's alias rather than its original name

Patch by Nicholas Wilson!

Differential Revision: https://reviews.llvm.org/D42076

llvm-svn: 322751

6 files changed, 37 insertions, 57 deletions

diff --git a/lld/test/wasm/alias.ll b/lld/test/wasm/alias.ll
index 6f9015a555a..a28280d8ef2 100644
--- a/lld/test/wasm/alias.ll
+++ b/lld/test/wasm/alias.ll
@@ -77,7 +77,7 @@ entry:
 ; CHECK-NEXT:     Name:            name
 ; CHECK-NEXT:     FunctionNames:   
 ; CHECK-NEXT:       - Index:           0
-; CHECK-NEXT:         Name:            start_alias
+; CHECK-NEXT:         Name:            _start
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Name:            __wasm_call_ctors
 ; CHECK-NEXT: ...
diff --git a/lld/test/wasm/relocatable.ll b/lld/test/wasm/relocatable.ll
index 615a9469f17..8803fd91d74 100644
--- a/lld/test/wasm/relocatable.ll
+++ b/lld/test/wasm/relocatable.ll
@@ -239,4 +239,6 @@ entry:
 ; CHECK-NEXT:         Name:            hello
 ; CHECK-NEXT:       - Index:           3
 ; CHECK-NEXT:         Name:            my_func
+; CHECK-NEXT:       - Index:           4
+; CHECK-NEXT:         Name:            func_comdat
 ; CHECK-NEXT: ...
diff --git a/lld/test/wasm/weak-symbols.ll b/lld/test/wasm/weak-symbols.ll
index 9c123347532..6fe8c9f8a1d 100644
--- a/lld/test/wasm/weak-symbols.ll
+++ b/lld/test/wasm/weak-symbols.ll
@@ -114,8 +114,12 @@ entry:
 ; CHECK-NEXT:     FunctionNames:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Name:            _start
+; CHECK-NEXT:       - Index:           1
+; CHECK-NEXT:         Name:            weakFn
 ; CHECK-NEXT:       - Index:           2
 ; CHECK-NEXT:         Name:            exportWeak1
+; CHECK-NEXT:       - Index:           3
+; CHECK-NEXT:         Name:            weakFn
 ; CHECK-NEXT:       - Index:           4
 ; CHECK-NEXT:         Name:            exportWeak2
 ; CHECK-NEXT:       - Index:           5
diff --git a/lld/wasm/InputChunks.h b/lld/wasm/InputChunks.h
index d5a9e5c668a..d8d03582cc3 100644
--- a/lld/wasm/InputChunks.h
+++ b/lld/wasm/InputChunks.h
@@ -112,8 +112,9 @@ class InputFunction : public InputChunk {
 public:
   InputFunction(const WasmSignature &S, const WasmFunction *Func,
                 const ObjFile *F)
-      : InputChunk(F), Signature(S), WrittenToNameSec(false), Function(Func) {}
+      : InputChunk(F), Signature(S), Function(Func) {}
 
+  virtual StringRef getName() const { return Function->Name; }
   StringRef getComdat() const override { return Function->Comdat; }
   uint32_t getOutputIndex() const { return OutputIndex.getValue(); }
   bool hasOutputIndex() const { return OutputIndex.hasValue(); }
@@ -121,8 +122,6 @@ public:
 
   const WasmSignature &Signature;
 
-  unsigned WrittenToNameSec : 1;
-
 protected:
   ArrayRef<uint8_t> data() const override {
     return File->CodeSection->Content.slice(getInputSectionOffset(),
@@ -138,12 +137,16 @@ protected:
 
 class SyntheticFunction : public InputFunction {
 public:
-  SyntheticFunction(const WasmSignature &S, ArrayRef<uint8_t> Body)
-      : InputFunction(S, nullptr, nullptr), Body(Body) {}
+  SyntheticFunction(const WasmSignature &S, ArrayRef<uint8_t> Body,
+                    StringRef Name)
+      : InputFunction(S, nullptr, nullptr), Name(Name), Body(Body) {}
+
+  StringRef getName() const override { return Name; }
 
 protected:
   ArrayRef<uint8_t> data() const override { return Body; }
 
+  StringRef Name;
   ArrayRef<uint8_t> Body;
 };
 
diff --git a/lld/wasm/Symbols.h b/lld/wasm/Symbols.h
index afda399965e..3e80944ae97 100644
--- a/lld/wasm/Symbols.h
+++ b/lld/wasm/Symbols.h
@@ -38,8 +38,7 @@ public:
     InvalidKind,
   };
 
-  Symbol(StringRef Name, uint32_t Flags)
-      : WrittenToNameSec(0), Flags(Flags), Name(Name) {}
+  Symbol(StringRef Name, uint32_t Flags) : Flags(Flags), Name(Name) {}
 
   Kind getKind() const { return SymbolKind; }
 
@@ -100,10 +99,6 @@ public:
   const Archive::Symbol &getArchiveSymbol() { return ArchiveSymbol; }
   InputFunction *getFunction() { return Function; }
 
-  // This bit is used by Writer::writeNameSection() to prevent
-  // symbols from being written to the symbol table more than once.
-  unsigned WrittenToNameSec : 1;
-
 protected:
   uint32_t Flags;
   uint32_t VirtualAddress = 0;
diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index 5cb5d55277a..14fc90e9751 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -469,59 +469,33 @@ void Writer::createLinkingSection() {
 
 // Create the custom "name" section containing debug symbol names.
 void Writer::createNameSection() {
-  // Create an array of all function sorted by function index space
-  std::vector<const Symbol *> Names;
-
-  auto AddToNames = [&](Symbol* S) {
-    if (!S->isFunction() || S->WrittenToNameSec)
-        return;
-    // We also need to guard against two different symbols (two different
-    // names) for the same wasm function.  While this is possible (aliases)
-    // it is not legal in the "name" section.
-    InputFunction *Function = S->getFunction();
-    if (Function) {
-      if (Function->WrittenToNameSec)
-        return;
-      Function->WrittenToNameSec = true;
-    }
-    S->WrittenToNameSec = true;
-    Names.emplace_back(S);
-  };
+  unsigned NumNames = ImportedFunctions.size();
+  for (const InputFunction *F : DefinedFunctions)
+    if (!F->getName().empty())
+      ++NumNames;
 
-  for (ObjFile *File : Symtab->ObjectFiles) {
-    Names.reserve(Names.size() + File->getSymbols().size());
-    DEBUG(dbgs() << "adding names from: " << File->getName() << "\n");
-    for (Symbol *S : File->getSymbols()) {
-      if (S->isWeak())
-        continue;
-      AddToNames(S);
-    }
-  }
-
-  DEBUG(dbgs() << "adding symtab names\n");
-  for (Symbol *S : Symtab->getSymbols()) {
-    DEBUG(dbgs() << "sym: " << S->getName() << "\n");
-    if (S->getFile())
-      continue;
-    AddToNames(S);
-  }
+  if (NumNames == 0)
+    return;
 
   SyntheticSection *Section = createSyntheticSection(WASM_SEC_CUSTOM, "name");
 
-  std::sort(Names.begin(), Names.end(), [](const Symbol *A, const Symbol *B) {
-    return A->getOutputIndex() < B->getOutputIndex();
-  });
-
   SubSection FunctionSubsection(WASM_NAMES_FUNCTION);
   raw_ostream &OS = FunctionSubsection.getStream();
-  writeUleb128(OS, Names.size(), "name count");
+  writeUleb128(OS, NumNames, "name count");
 
-  // We have to iterate through the inputs twice so that all the imports
-  // appear first before any of the local function names.
-  for (const Symbol *S : Names) {
-    writeUleb128(OS, S->getOutputIndex(), "func index");
+  // Names must appear in function index order.  As it happens ImportedFunctions
+  // and DefinedFunctions are numbers in order with imported functions coming
+  // first.
+  for (const Symbol *S : ImportedFunctions) {
+    writeUleb128(OS, S->getOutputIndex(), "import index");
     writeStr(OS, S->getName(), "symbol name");
   }
+  for (const InputFunction *F : DefinedFunctions) {
+    if (!F->getName().empty()) {
+      writeUleb128(OS, F->getOutputIndex(), "func index");
+      writeStr(OS, F->getName(), "symbol name");
+    }
+  }
 
   FunctionSubsection.finalizeContents();
   FunctionSubsection.writeToStream(Section->getStream());
@@ -784,7 +758,9 @@ void Writer::createCtorFunction() {
   ArrayRef<uint8_t> BodyArray(
       reinterpret_cast<const uint8_t *>(CtorFunctionBody.data()),
       CtorFunctionBody.size());
-  CtorFunction = llvm::make_unique<SyntheticFunction>(Signature, BodyArray);
+  CtorFunction = llvm::make_unique<SyntheticFunction>(
+      Signature, BodyArray, Config->CtorSymbol->getName());
+  CtorFunction->setOutputIndex(FunctionIndex);
   DefinedFunctions.emplace_back(CtorFunction.get());
 }