PNaCl Dynamic Linking: Force __pnacl_pso_root to be an external declaration.

src/IceGlobalInits.h

@@ -71,6 +71,10 @@ public:
     return Linkage == llvm::GlobalValue::InternalLinkage;
   }
   llvm::GlobalValue::LinkageTypes getLinkage() const { return Linkage; }
+  void setLinkage(llvm::GlobalValue::LinkageTypes L) {
+    assert(!hasName());
+    Linkage = L;
+  }
   bool isExternal() const {
     return Linkage == llvm::GlobalValue::ExternalLinkage;
   }
@@ -90,6 +94,10 @@ public:
     return isInternal() ? "internal" : "external";
   }
 
+  /// Returns true if the name of this GlobalDeclaration indicates that it
+  /// should have ExternalLinkage (as a special case).
+  virtual bool isPNaClABIExternalName(const IceString &Name) const = 0;
+
 protected:
   GlobalDeclaration(GlobalDeclarationKind Kind,
                     llvm::GlobalValue::LinkageTypes Linkage)
@@ -109,7 +117,7 @@ protected:
   }
 
   const GlobalDeclarationKind Kind;
-  const llvm::GlobalValue::LinkageTypes Linkage;
+  llvm::GlobalValue::LinkageTypes Linkage;
   IceString Name;
 };
 
@@ -142,9 +150,11 @@ public:
 
   /// Returns true if linkage is correct for the function declaration.
   bool verifyLinkageCorrect(const GlobalContext *Ctx) const {
-    if (isPNaClABIExternalName() || isIntrinsicName(Ctx))
+    if (isPNaClABIExternalName(getName()) || isIntrinsicName(Ctx)) {
       return Linkage == llvm::GlobalValue::ExternalLinkage;
-    return verifyLinkageDefault(Ctx);
+    } else {
+      return verifyLinkageDefault(Ctx);
+    }
   }
 
   /// Validates that the type signature of the function is correct. Returns true
@@ -184,9 +194,8 @@ private:
       : GlobalDeclaration(FunctionDeclarationKind, Linkage),
         Signature(Signature), CallingConv(CallingConv), IsProto(IsProto) {}
 
-  bool isPNaClABIExternalName() const {
-    const char *Name = getName().c_str();
-    return strcmp(Name, "_start") == 0 || strcmp(Name, "__pnacl_pso_root") == 0;
+  bool isPNaClABIExternalName(const IceString &Name) const override {
+    return Name == "_start";
   }
 
   bool isIntrinsicName(const GlobalContext *Ctx) const {
@@ -414,10 +423,13 @@ public:
 
   /// Prints out the definition of the global variable declaration (including
   /// initialization).
-  virtual void dump(Ostream &Stream) const;
+  virtual void dump(Ostream &Stream) const override;
 
   /// Returns true if linkage is correct for the variable declaration.
   bool verifyLinkageCorrect(const GlobalContext *Ctx) const {
+    if (isPNaClABIExternalName(getName())) {
+      return Linkage == llvm::GlobalValue::ExternalLinkage;
+    }
     return verifyLinkageDefault(Ctx);
   }
 
@@ -433,6 +445,10 @@ public:
 
   void discardInitializers() { Initializers = nullptr; }
 
+  bool isPNaClABIExternalName(const IceString &Name) const override {
+    return Name == "__pnacl_pso_root";
+  }
+
 private:
   /// List of initializers for the declared variable.
   std::unique_ptr<InitializerListType> Initializers;

src/PNaClTranslator.cpp

@@ -3043,8 +3043,17 @@ private:
 
 void ModuleValuesymtabParser::setValueName(NaClBcIndexSize_t Index,
                                            StringType &Name) {
-  Context->getGlobalDeclarationByID(Index)
-      ->setName(StringRef(Name.data(), Name.size()));
+  Ice::GlobalDeclaration *Decl = Context->getGlobalDeclarationByID(Index);
+  if (llvm::isa<Ice::VariableDeclaration>(Decl) &&
+      Decl->isPNaClABIExternalName(Name.str())) {
+    // Force linkage of (specific) Global Variables be external for the PNaCl
+    // ABI. PNaCl bitcode has a linkage field for Functions, but not for
+    // GlobalVariables (because the latter is not needed for pexes, so it has
+    // been removed).
+    Decl->setLinkage(llvm::GlobalValue::ExternalLinkage);
+  }
+
+  Decl->setName(StringRef(Name.data(), Name.size()));
 }
 
 void ModuleValuesymtabParser::setBbName(NaClBcIndexSize_t Index,

tests_lit/llvm2ice_tests/external_declaration.ll

+; Tests that any symbols with special names have specially treated linkage.
+
+; RUN: %if --need=allow_dump --command %p2i -i %s --filetype=asm \
+; RUN:   --args -nonsfi=0 \
+; RUN:   | %if --need=allow_dump --command FileCheck %s
+
+; Verify that "__pnacl_pso_root", a specially named symbol, is made global, but
+; other global variables are not.
+@__pnacl_pso_root = constant [4 x i8] c"abcd";
+@__pnacl_pso_not_root = constant [4 x i8] c"efgh";
+
+; CHECK: .globl __pnacl_pso_root
+; CHECK-NOT: .globl __pnacl_pso_not_root