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).
https://github.com/llvm-mirror/clang/commit/746b78de7812bc785fbb5207b788348040b23fa7

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

llvm-svn: 337420

1 files changed, 79 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index a754cc912d9..b6381dc1e4b 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/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.
 ///