[CUDA] [AST] Allow isInlineDefinitionExternallyVisible to be called on functions without bodies.

Summary:
In CUDA compilation, we call isInlineDefinitionExternallyVisible (via
getGVALinkageForFunction) on functions while parsing their definitions.

At the point in time when we call getGVALinkageForFunction, we haven't
yet added the body to the function, so we trip this assert.  But as far
as I can tell, this is harmless.

To work around this, we add a new flag to FunctionDecl, "WillHaveBody".

There was other code that was working around the existing assert with a
really awful hack -- this change lets us get rid of that hack.

Reviewers: rsmith, tra

Subscribers: aemerson, cfe-commits

Differential Revision: https://reviews.llvm.org/D25640

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@285410 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/Decl.h

@@ -1632,6 +1632,11 @@ private:
   /// skipped.
   unsigned HasSkippedBody : 1;
 
+  /// Indicates if the function declaration will have a body, once we're done
+  /// parsing it.  (We don't set it to false when we're done parsing, in the
+  /// hopes this is simpler.)
+  unsigned WillHaveBody : 1;
+
   /// \brief End part of this FunctionDecl's source range.
   ///
   /// We could compute the full range in getSourceRange(). However, when we're
@@ -1701,25 +1706,21 @@ private:
 
 protected:
   FunctionDecl(Kind DK, ASTContext &C, DeclContext *DC, SourceLocation StartLoc,
-               const DeclarationNameInfo &NameInfo,
-               QualType T, TypeSourceInfo *TInfo,
-               StorageClass S, bool isInlineSpecified,
+               const DeclarationNameInfo &NameInfo, QualType T,
+               TypeSourceInfo *TInfo, StorageClass S, bool isInlineSpecified,
                bool isConstexprSpecified)
-    : DeclaratorDecl(DK, DC, NameInfo.getLoc(), NameInfo.getName(), T, TInfo,
-                     StartLoc),
-      DeclContext(DK),
-      redeclarable_base(C),
-      ParamInfo(nullptr), Body(),
-      SClass(S),
-      IsInline(isInlineSpecified), IsInlineSpecified(isInlineSpecified),
-      IsVirtualAsWritten(false), IsPure(false), HasInheritedPrototype(false),
-      HasWrittenPrototype(true), IsDeleted(false), IsTrivial(false),
-      IsDefaulted(false), IsExplicitlyDefaulted(false),
-      HasImplicitReturnZero(false), IsLateTemplateParsed(false),
-      IsConstexpr(isConstexprSpecified), UsesSEHTry(false),
-      HasSkippedBody(false), EndRangeLoc(NameInfo.getEndLoc()),
-      TemplateOrSpecialization(),
-      DNLoc(NameInfo.getInfo()) {}
+      : DeclaratorDecl(DK, DC, NameInfo.getLoc(), NameInfo.getName(), T, TInfo,
+                       StartLoc),
+        DeclContext(DK), redeclarable_base(C), ParamInfo(nullptr), Body(),
+        SClass(S), IsInline(isInlineSpecified),
+        IsInlineSpecified(isInlineSpecified), IsVirtualAsWritten(false),
+        IsPure(false), HasInheritedPrototype(false), HasWrittenPrototype(true),
+        IsDeleted(false), IsTrivial(false), IsDefaulted(false),
+        IsExplicitlyDefaulted(false), HasImplicitReturnZero(false),
+        IsLateTemplateParsed(false), IsConstexpr(isConstexprSpecified),
+        UsesSEHTry(false), HasSkippedBody(false), WillHaveBody(false),
+        EndRangeLoc(NameInfo.getEndLoc()), TemplateOrSpecialization(),
+        DNLoc(NameInfo.getInfo()) {}
 
   typedef Redeclarable<FunctionDecl> redeclarable_base;
   FunctionDecl *getNextRedeclarationImpl() override {
@@ -2001,6 +2002,10 @@ public:
   bool hasSkippedBody() const { return HasSkippedBody; }
   void setHasSkippedBody(bool Skipped = true) { HasSkippedBody = Skipped; }
 
+  /// True if this function will eventually have a body, once it's fully parsed.
+  bool willHaveBody() const { return WillHaveBody; }
+  void setWillHaveBody(bool V = true) { WillHaveBody = V; }
+
   void setPreviousDeclaration(FunctionDecl * PrevDecl);
 
   FunctionDecl *getCanonicalDecl() override;

lib/AST/Decl.cpp

@@ -2933,7 +2933,7 @@ static bool RedeclForcesDefC99(const FunctionDecl *Redecl) {
 /// of redeclarations of the given functions causes
 /// isInlineDefinitionExternallyVisible to change from false to true.
 bool FunctionDecl::doesDeclarationForceExternallyVisibleDefinition() const {
-  assert(!doesThisDeclarationHaveABody() &&
+  assert(!doesThisDeclarationHaveABody() && !willHaveBody() &&
          "Must have a declaration without a body.");
 
   ASTContext &Context = getASTContext();
@@ -3048,7 +3048,8 @@ const Attr *FunctionDecl::getUnusedResultAttr() const {
 /// an externally visible symbol, but "extern inline" will not create an 
 /// externally visible symbol.
 bool FunctionDecl::isInlineDefinitionExternallyVisible() const {
-  assert(doesThisDeclarationHaveABody() && "Must have the function definition");
+  assert(doesThisDeclarationHaveABody() ||
+         willHaveBody() && "Must be a function definition");
   assert(isInlined() && "Function must be inline");
   ASTContext &Context = getASTContext();
   

lib/Sema/SemaDecl.cpp

@@ -5762,23 +5762,7 @@ static bool isFunctionDefinitionDiscarded(Sema &S, FunctionDecl *FD) {
     return false;
 
   // Okay, go ahead and call the relatively-more-expensive function.
-
-#ifndef NDEBUG
-  // AST quite reasonably asserts that it's working on a function
-  // definition.  We don't really have a way to tell it that we're
-  // currently defining the function, so just lie to it in +Asserts
-  // builds.  This is an awful hack.
-  FD->setLazyBody(1);
-#endif
-
-  bool isC99Inline =
-      S.Context.GetGVALinkageForFunction(FD) == GVA_AvailableExternally;
-
-#ifndef NDEBUG
-  FD->setLazyBody(0);
-#endif
-
-  return isC99Inline;
+  return S.Context.GetGVALinkageForFunction(FD) == GVA_AvailableExternally;
 }
 
 /// Determine whether a variable is extern "C" prior to attaching
@@ -11487,6 +11471,11 @@ Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
       return D;
   }
 
+  // Mark this function as "will have a body eventually".  This lets users to
+  // call e.g. isInlineDefinitionExternallyVisible while we're still parsing
+  // this function.
+  FD->setWillHaveBody();
+
   // If we are instantiating a generic lambda call operator, push
   // a LambdaScopeInfo onto the function stack.  But use the information
   // that's already been calculated (ActOnLambdaExpr) to prime the current

test/SemaCUDA/gnu-inline.cu

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+#include "Inputs/cuda.h"
+
+// expected-no-diagnostics
+
+// Check that we can handle gnu_inline functions when compiling in CUDA mode.
+
+void foo();
+inline __attribute__((gnu_inline)) void bar() { foo(); }