Emit section information for extern variables.

Currently, if _attribute_((section())) is used for extern variables,
section information is not emitted in generated IR when the variables are used.
This is expected since sections are not generated for external linkage objects.
However NiosII requires this information as it uses special GP-relative accesses
for any objects that use attribute section (.sdata). GCC keeps this attribute in
  middle-end.

This change emits the section information for all targets.

Patch By: Elizabeth Andrews

Differential Revision:https://reviews.llvm.org/D36487

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@314262 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 1420dabf1e9d89aaf3482114a72944fe81cae35b..0b3c9fed6bdb041c27e009a1f99d1831bcf6deef 100644 (file)
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2620,6 +2620,8 @@ def err_attribute_section_invalid_for_target : Error<
   "argument to 'section' attribute is not valid for this target: %0">;
 def warn_mismatched_section : Warning<
   "section 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_anonymous_property: Error<
   "anonymous property is not supported">;

diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 03a3e36b831abf6d9bd8382a0707e7ff765d09b4..89185c89518a39f4536ada8fe0e957f288ae7f19 100644 (file)
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -2432,6 +2432,12 @@ CodeGenModule::GetOrCreateLLVMGlobal(StringRef MangledName,
       EmitGlobalVarDefinition(D);
     }
 
+    // Emit section information for extern variables.
+    if (D->hasExternalStorage()) {
+      if (const SectionAttr *SA = D->getAttr<SectionAttr>())
+        GV->setSection(SA->getName());
+    }
+
     // Handle XCore specific ABI requirements.
     if (getTriple().getArch() == llvm::Triple::xcore &&
         D->getLanguageLinkage() == CLanguageLinkage &&

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 33f02c5b7f4bf27c2e47be44e4e905205afbfca8..c99dbd944b052f603ff344ff1758566fb137c6c9 100644 (file)
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -2607,6 +2607,16 @@ void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
     }
   }
 
+  // This redeclaration adds a section attribute.
+  if (New->hasAttr<SectionAttr>() && !Old->hasAttr<SectionAttr>()) {
+    if (auto *VD = dyn_cast<VarDecl>(New)) {
+      if (VD->isThisDeclarationADefinition() != VarDecl::Definition) {
+        Diag(New->getLocation(), diag::warn_attribute_section_on_redeclaration);
+        Diag(Old->getLocation(), diag::note_previous_declaration);
+      }
+    }
+  }
+
   if (!Old->hasAttrs())
     return;
 

diff --git a/test/Sema/attr-section.c b/test/Sema/attr-section.c
index c64b10d80ff64324010491576151bcee950357bd..2fb4dbd6bfd7c3934893919f85ff0c535cd30e05 100644 (file)
--- a/test/Sema/attr-section.c
+++ b/test/Sema/attr-section.c
@@ -19,3 +19,7 @@ void __attribute__((section("foo,zed"))) test2(void); // expected-note {{previou
 void __attribute__((section("bar,zed"))) test2(void) {} // expected-warning {{section does not match previous declaration}}
 
 enum __attribute__((section("NEAR,x"))) e { one }; // expected-error {{'section' attribute only applies to functions, methods, properties, and global variables}}
+
+extern int a; // expected-note {{previous declaration is here}}
+int *b = &a;
+extern int a __attribute__((section("foo,zed"))); // expected-warning {{section attribute is specified on redeclared variable}}