Add support for __declspec(code_seg("segname"))

This patch uses CodeSegAttr to represent __declspec(code_seg) rather than 
building on the existing support for #pragma code_seg.
The code_seg declspec is applied on functions and classes. This attribute 
enables the placement of code into separate named segments, including compiler-
generated codes and template instantiations.

For more information, please see the following:
https://msdn.microsoft.com/en-us/library/dn636922.aspx

This patch fixes the regression for the support for attribute ((section).
llvm-mirror/clang@746b78d

Patch by Soumi Manna (Manna)
Differential Revision: https://reviews.llvm.org/D48841

llvm-svn: 337420

clang/include/clang/Basic/Attr.td

@@ -1770,6 +1770,13 @@ def Section : InheritableAttr {
   let Documentation = [SectionDocs];
 }
 
+def CodeSeg : InheritableAttr {
+  let Spellings = [Declspec<"code_seg">];
+  let Args = [StringArgument<"Name">];
+  let Subjects = SubjectList<[Function, CXXRecord], ErrorDiag>;
+  let Documentation = [CodeSegDocs];
+}
+
 def PragmaClangBSSSection : InheritableAttr {
   // This attribute has no spellings as it is only ever created implicitly.
   let Spellings = [];

clang/include/clang/Basic/AttrDocs.td

@@ -306,6 +306,18 @@ An example of how to use ``alloc_size``
   }];
 }
 
+def CodeSegDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+The ``__declspec(code_seg)`` attribute enables the placement of code into separate
+named segments that can be paged or locked in memory individually. This attribute
+is used to control the placement of instantiated templates and compiler-generated
+code. See the documentation for `__declspec(code_seg)`_ on MSDN.
+
+.. _`__declspec(code_seg)`: http://msdn.microsoft.com/en-us/library/dn636922.aspx
+  }];
+}
+
 def AllocAlignDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2668,11 +2668,19 @@ def err_only_annotate_after_access_spec : Error<
   "access specifier can only have annotation attributes">;
 
 def err_attribute_section_invalid_for_target : Error<
-  "argument to 'section' attribute is not valid for this target: %0">;
+  "argument to %select{'code_seg'|'section'}1 attribute is not valid for this target: %0">;
 def warn_mismatched_section : Warning<
-  "section does not match previous declaration">, InGroup<Section>;
+  "%select{codeseg|section}0 does not match previous declaration">, InGroup<Section>;
 def warn_attribute_section_on_redeclaration : Warning<
   "section attribute is specified on redeclared variable">, InGroup<Section>;
+def err_mismatched_code_seg_base : Error<
+  "derived class must specify the same code segment as its base classes">;
+def err_mismatched_code_seg_override : Error<
+  "overriding virtual function must specify the same code segment as its overridden function">;
+def err_conflicting_codeseg_attribute : Error<
+  "conflicting code segment specifiers">;
+def warn_duplicate_codeseg_attribute : Warning<
+  "duplicate code segment specifiers">, InGroup<Section>;
 
 def err_anonymous_property: Error<
   "anonymous property is not supported">;

clang/include/clang/Sema/Sema.h

@@ -1952,6 +1952,7 @@ class Sema {
   bool shouldLinkDependentDeclWithPrevious(Decl *D, Decl *OldDecl);
   void CheckMain(FunctionDecl *FD, const DeclSpec &D);
   void CheckMSVCRTEntryPoint(FunctionDecl *FD);
+  Attr *getImplicitCodeSegOrSectionAttrForFunction(const FunctionDecl *FD, bool IsDefinition);
   Decl *ActOnParamDeclarator(Scope *S, Declarator &D);
   ParmVarDecl *BuildParmVarDeclForTypedef(DeclContext *DC,
                                           SourceLocation Loc,
@@ -2446,6 +2447,8 @@ class Sema {
                               int FirstArg, unsigned AttrSpellingListIndex);
   SectionAttr *mergeSectionAttr(Decl *D, SourceRange Range, StringRef Name,
                                 unsigned AttrSpellingListIndex);
+  CodeSegAttr *mergeCodeSegAttr(Decl *D, SourceRange Range, StringRef Name,
+                                unsigned AttrSpellingListIndex);
   AlwaysInlineAttr *mergeAlwaysInlineAttr(Decl *D, SourceRange Range,
                                           IdentifierInfo *Ident,
                                           unsigned AttrSpellingListIndex);
@@ -5852,6 +5855,7 @@ class Sema {
   /// ensure that referenceDLLExportedClassMethods is called some point later
   /// when all outer classes of Class are complete.
   void checkClassLevelDLLAttribute(CXXRecordDecl *Class);
+  void checkClassLevelCodeSegAttribute(CXXRecordDecl *Class);
 
   void referenceDLLExportedClassMethods();
 

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1387,8 +1387,10 @@ void CodeGenModule::setNonAliasAttributes(GlobalDecl GD,
         F->addAttributes(llvm::AttributeList::FunctionIndex, Attrs);
       }
     }
-
-    if (const SectionAttr *SA = D->getAttr<SectionAttr>())
+
+    if (const auto *CSA = D->getAttr<CodeSegAttr>())
+      GO->setSection(CSA->getName());
+    else if (const auto *SA = D->getAttr<SectionAttr>())
       GO->setSection(SA->getName());
   }
 
@@ -1485,8 +1487,10 @@ void CodeGenModule::SetFunctionAttributes(GlobalDecl GD, llvm::Function *F,
   setLinkageForGV(F, FD);
   setGVProperties(F, FD);
 
-  if (const SectionAttr *SA = FD->getAttr<SectionAttr>())
-    F->setSection(SA->getName());
+  if (const auto *CSA = FD->getAttr<CodeSegAttr>())
+    F->setSection(CSA->getName());
+  else if (const auto *SA = FD->getAttr<SectionAttr>())
+     F->setSection(SA->getName());
 
   if (FD->isReplaceableGlobalAllocationFunction()) {
     // A replaceable global allocation function does not act like a builtin by

clang/lib/Sema/SemaDecl.cpp

@@ -2452,6 +2452,9 @@ static bool mergeDeclAttribute(Sema &S, NamedDecl *D,
   else if (const auto *SA = dyn_cast<SectionAttr>(Attr))
     NewAttr = S.mergeSectionAttr(D, SA->getRange(), SA->getName(),
                                  AttrSpellingListIndex);
+  else if (const auto *CSA = dyn_cast<CodeSegAttr>(Attr))
+    NewAttr = S.mergeCodeSegAttr(D, CSA->getRange(), CSA->getName(),
+                                 AttrSpellingListIndex);
   else if (const auto *IA = dyn_cast<MSInheritanceAttr>(Attr))
     NewAttr = S.mergeMSInheritanceAttr(D, IA->getRange(), IA->getBestCase(),
                                        AttrSpellingListIndex,
@@ -2670,6 +2673,15 @@ void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
     }
   }
 
+  // Redeclaration adds code-seg attribute.
+  const auto *NewCSA = New->getAttr<CodeSegAttr>();
+  if (NewCSA && !Old->hasAttr<CodeSegAttr>() &&
+      !NewCSA->isImplicit() && isa<CXXMethodDecl>(New)) {
+    Diag(New->getLocation(), diag::warn_mismatched_section)
+         << 0 /*codeseg*/;
+    Diag(Old->getLocation(), diag::note_previous_declaration);
+  }
+
   if (!Old->hasAttrs())
     return;
 
@@ -8723,6 +8735,15 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       NewFD->dropAttr<SectionAttr>();
   }
 
+  // Apply an implicit CodeSegAttr from class declspec or
+  // apply an implicit SectionAttr from #pragma code_seg if active.
+  if (!NewFD->hasAttr<CodeSegAttr>()) {
+    if (Attr *SAttr = getImplicitCodeSegOrSectionAttrForFunction(NewFD,
+                                                                 D.isFunctionDefinition())) {
+      NewFD->addAttr(SAttr);
+    }
+  }
+
   // Handle attributes.
   ProcessDeclAttributes(S, NewFD, D);
 
@@ -9170,6 +9191,64 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   return NewFD;
 }
 
+/// Return a CodeSegAttr from a containing class.  The Microsoft docs say
+/// when __declspec(code_seg) "is applied to a class, all member functions of
+/// the class and nested classes -- this includes compiler-generated special
+/// member functions -- are put in the specified segment."
+/// The actual behavior is a little more complicated. The Microsoft compiler
+/// won't check outer classes if there is an active value from #pragma code_seg.
+/// The CodeSeg is always applied from the direct parent but only from outer
+/// classes when the #pragma code_seg stack is empty. See:
+/// https://reviews.llvm.org/D22931, the Microsoft feedback page is no longer
+/// available since MS has removed the page.
+static Attr *getImplicitCodeSegAttrFromClass(Sema &S, const FunctionDecl *FD) {
+  const auto *Method = dyn_cast<CXXMethodDecl>(FD);
+  if (!Method)
+    return nullptr;
+  const CXXRecordDecl *Parent = Method->getParent();
+  if (const auto *SAttr = Parent->getAttr<CodeSegAttr>()) {
+    Attr *NewAttr = SAttr->clone(S.getASTContext());
+    NewAttr->setImplicit(true);
+    return NewAttr;
+  }
+
+  // The Microsoft compiler won't check outer classes for the CodeSeg
+  // when the #pragma code_seg stack is active.
+  if (S.CodeSegStack.CurrentValue)
+   return nullptr;
+
+  while ((Parent = dyn_cast<CXXRecordDecl>(Parent->getParent()))) {
+    if (const auto *SAttr = Parent->getAttr<CodeSegAttr>()) {
+      Attr *NewAttr = SAttr->clone(S.getASTContext());
+      NewAttr->setImplicit(true);
+      return NewAttr;
+    }
+  }
+  return nullptr;
+}
+
+/// Returns an implicit CodeSegAttr if a __declspec(code_seg) is found on a
+/// containing class. Otherwise it will return implicit SectionAttr if the
+/// function is a definition and there is an active value on CodeSegStack
+/// (from the current #pragma code-seg value).
+///
+/// \param FD Function being declared.
+/// \param IsDefinition Whether it is a definition or just a declarartion.
+/// \returns A CodeSegAttr or SectionAttr to apply to the function or
+///          nullptr if no attribute should be added.
+Attr *Sema::getImplicitCodeSegOrSectionAttrForFunction(const FunctionDecl *FD,
+                                                       bool IsDefinition) {
+  if (Attr *A = getImplicitCodeSegAttrFromClass(*this, FD))
+    return A;
+  if (!FD->hasAttr<SectionAttr>() && IsDefinition &&
+      CodeSegStack.CurrentValue) {
+    return SectionAttr::CreateImplicit(getASTContext(),
+                                       SectionAttr::Declspec_allocate,
+                                       CodeSegStack.CurrentValue->getString(),
+                                       CodeSegStack.CurrentPragmaLocation);
+  }
+  return nullptr;
+}
 /// Checks if the new declaration declared in dependent context must be
 /// put in the same redeclaration chain as the specified declaration.
 ///

clang/lib/Sema/SemaDeclAttr.cpp

@@ -2825,10 +2825,18 @@ static void handleVecTypeHint(Sema &S, Decl *D, const ParsedAttr &AL) {
 SectionAttr *Sema::mergeSectionAttr(Decl *D, SourceRange Range,
                                     StringRef Name,
                                     unsigned AttrSpellingListIndex) {
+  // Explicit or partial specializations do not inherit
+  // the section attribute from the primary template.
+  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
+    if (AttrSpellingListIndex == SectionAttr::Declspec_allocate &&
+        FD->isFunctionTemplateSpecialization())
+      return nullptr;
+  }
   if (SectionAttr *ExistingAttr = D->getAttr<SectionAttr>()) {
     if (ExistingAttr->getName() == Name)
       return nullptr;
-    Diag(ExistingAttr->getLocation(), diag::warn_mismatched_section);
+    Diag(ExistingAttr->getLocation(), diag::warn_mismatched_section)
+         << 1 /*section*/;
     Diag(Range.getBegin(), diag::note_previous_attribute);
     return nullptr;
   }
@@ -2839,7 +2847,8 @@ SectionAttr *Sema::mergeSectionAttr(Decl *D, SourceRange Range,
 bool Sema::checkSectionName(SourceLocation LiteralLoc, StringRef SecName) {
   std::string Error = Context.getTargetInfo().isValidSectionSpecifier(SecName);
   if (!Error.empty()) {
-    Diag(LiteralLoc, diag::err_attribute_section_invalid_for_target) << Error;
+    Diag(LiteralLoc, diag::err_attribute_section_invalid_for_target) << Error
+         << 1 /*'section'*/;	  
     return false;
   }
   return true;
@@ -2870,6 +2879,59 @@ static void handleSectionAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
     D->addAttr(NewAttr);
 }
 
+static bool checkCodeSegName(Sema&S, SourceLocation LiteralLoc, StringRef CodeSegName) {
+  std::string Error = S.Context.getTargetInfo().isValidSectionSpecifier(CodeSegName);
+  if (!Error.empty()) {
+    S.Diag(LiteralLoc, diag::err_attribute_section_invalid_for_target) << Error
+           << 0 /*'code-seg'*/;
+    return false;
+  }
+  return true;
+}
+
+CodeSegAttr *Sema::mergeCodeSegAttr(Decl *D, SourceRange Range,
+                                    StringRef Name,
+                                    unsigned AttrSpellingListIndex) {
+  // Explicit or partial specializations do not inherit
+  // the code_seg attribute from the primary template.
+  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
+    if (FD->isFunctionTemplateSpecialization())
+      return nullptr;
+  }
+  if (const auto *ExistingAttr = D->getAttr<CodeSegAttr>()) {
+    if (ExistingAttr->getName() == Name)
+      return nullptr;
+    Diag(ExistingAttr->getLocation(), diag::warn_mismatched_section)
+         << 0 /*codeseg*/;
+    Diag(Range.getBegin(), diag::note_previous_attribute);
+    return nullptr;
+  }
+  return ::new (Context) CodeSegAttr(Range, Context, Name,
+                                     AttrSpellingListIndex);
+}
+
+static void handleCodeSegAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  StringRef Str;
+  SourceLocation LiteralLoc;
+  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &LiteralLoc))
+    return;
+  if (!checkCodeSegName(S, LiteralLoc, Str))
+    return;
+  if (const auto *ExistingAttr = D->getAttr<CodeSegAttr>()) {
+    if (!ExistingAttr->isImplicit()) {
+      S.Diag(AL.getLoc(),
+             ExistingAttr->getName() == Str
+             ? diag::warn_duplicate_codeseg_attribute
+             : diag::err_conflicting_codeseg_attribute);
+      return;
+    }
+    D->dropAttr<CodeSegAttr>();
+  }
+  if (CodeSegAttr *CSA = S.mergeCodeSegAttr(D, AL.getRange(), Str,
+                                            AL.getAttributeSpellingListIndex()))
+    D->addAttr(CSA);
+}
+
 // Check for things we'd like to warn about. Multiversioning issues are
 // handled later in the process, once we know how many exist.
 bool Sema::checkTargetAttr(SourceLocation LiteralLoc, StringRef AttrStr) {
@@ -6120,6 +6182,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_Section:
     handleSectionAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_CodeSeg:
+    handleCodeSegAttr(S, D, AL);
+    break;
   case ParsedAttr::AT_Target:
     handleTargetAttr(S, D, AL);
     break;

clang/lib/Sema/SemaDeclCXX.cpp

@@ -2243,6 +2243,19 @@ Sema::CheckBaseSpecifier(CXXRecordDecl *Class,
   CXXRecordDecl *CXXBaseDecl = cast<CXXRecordDecl>(BaseDecl);
   assert(CXXBaseDecl && "Base type is not a C++ type");
 
+  // Microsoft docs say:
+  // "If a base-class has a code_seg attribute, derived classes must have the
+  // same attribute."
+  const auto *BaseCSA = CXXBaseDecl->getAttr<CodeSegAttr>();
+  const auto *DerivedCSA = Class->getAttr<CodeSegAttr>();
+  if ((DerivedCSA || BaseCSA) &&
+      (!BaseCSA || !DerivedCSA || BaseCSA->getName() != DerivedCSA->getName())) {
+    Diag(Class->getLocation(), diag::err_mismatched_code_seg_base);
+    Diag(CXXBaseDecl->getLocation(), diag::note_base_class_specified_here)
+      << CXXBaseDecl;
+    return nullptr;
+  }
+
   // A class which contains a flexible array member is not suitable for use as a
   // base class:
   //   - If the layout determines that a base comes before another base,
@@ -5614,6 +5627,16 @@ static void checkForMultipleExportedDefaultConstructors(Sema &S,
   }
 }
 
+void Sema::checkClassLevelCodeSegAttribute(CXXRecordDecl *Class) {
+  // Mark any compiler-generated routines with the implicit code_seg attribute.
+  for (auto *Method : Class->methods()) {
+    if (Method->isUserProvided())
+      continue;
+    if (Attr *A = getImplicitCodeSegOrSectionAttrForFunction(Method, /*IsDefinition=*/true))
+      Method->addAttr(A);
+  }
+}
+
 /// Check class-level dllimport/dllexport attribute.
 void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
   Attr *ClassAttr = getDLLAttr(Class);
@@ -6122,6 +6145,7 @@ void Sema::CheckCompletedCXXClass(CXXRecordDecl *Record) {
   }
 
   checkClassLevelDLLAttribute(Record);
+  checkClassLevelCodeSegAttribute(Record);
 
   bool ClangABICompat4 =
       Context.getLangOpts().getClangABICompat() <= LangOptions::ClangABI::Ver4;
@@ -14589,6 +14613,16 @@ bool Sema::CheckOverridingFunctionAttributes(const CXXMethodDecl *New,
       }
   }
 
+  // Virtual overrides must have the same code_seg.
+  const auto *OldCSA = Old->getAttr<CodeSegAttr>();
+  const auto *NewCSA = New->getAttr<CodeSegAttr>();
+  if ((NewCSA || OldCSA) &&
+      (!OldCSA || !NewCSA || NewCSA->getName() != OldCSA->getName())) {
+    Diag(New->getLocation(), diag::err_mismatched_code_seg_override);
+    Diag(Old->getLocation(), diag::note_previous_declaration);
+    return true;
+  }
+
   CallingConv NewCC = NewFT->getCallConv(), OldCC = OldFT->getCallConv();
 
   // If the calling conventions match, everything is fine

clang/lib/Sema/SemaLambda.cpp

@@ -913,6 +913,10 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
   // This represents the function body for the lambda function, check if we
   // have to apply optnone due to a pragma.
   AddRangeBasedOptnone(Method);
+
+  // code_seg attribute on lambda apply to the method.
+  if (Attr *A = getImplicitCodeSegOrSectionAttrForFunction(Method, /*IsDefinition=*/true))
+    Method->addAttr(A);
 
   // Attributes on the lambda apply to the method.  
   ProcessDeclAttributes(CurScope, Method, ParamInfo);