r214828 - MS ABI: Aligned tentative definitions don't have CommonLinkage

[David Majnemer]

Author: majnemer
Date: Mon Aug  4 19:01:13 2014
New Revision: 214828

URL: http://llvm.org/viewvc/llvm-project?rev=214828&view=rev
Log:
MS ABI: Aligned tentative definitions don't have CommonLinkage

int __declspec(align(16)) foo; is a tentative definition but the storage
for that variable should not have CommonLinkage.

Added:
    cfe/trunk/test/CodeGen/ms-align-tentative.c
Modified:
    cfe/trunk/lib/CodeGen/CodeGenModule.cpp

Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=214828&r1=214827&r2=214828&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Mon Aug  4 19:01:13 2014
@@ -1951,7 +1951,8 @@ void CodeGenModule::EmitGlobalVarDefinit
       DI->EmitGlobalVariable(GV, D);
 }
 
-static bool isVarDeclStrongDefinition(const VarDecl *D, bool NoCommon) {
+static bool isVarDeclStrongDefinition(const ASTContext &Context,
+                                      const VarDecl *D, bool NoCommon) {
   // Don't give variables common linkage if -fno-common was specified unless it
   // was overridden by a NoCommon attribute.
   if ((NoCommon || D->hasAttr<NoCommonAttr>()) && !D->hasAttr<CommonAttr>())
@@ -1976,6 +1977,12 @@ static bool isVarDeclStrongDefinition(co
   if (D->hasAttr<WeakImportAttr>())
     return true;
 
+  // Declarations with a required alignment do not have common linakge in MSVC
+  // mode.
+  if (Context.getLangOpts().MSVCCompat &&
+      (Context.isAlignmentRequired(D->getType()) || D->hasAttr<AlignedAttr>()))
+    return true;
+
   return false;
 }
 
@@ -2022,7 +2029,8 @@ llvm::GlobalValue::LinkageTypes CodeGenM
   // C++ doesn't have tentative definitions and thus cannot have common
   // linkage.
   if (!getLangOpts().CPlusPlus && isa<VarDecl>(D) &&
-      !isVarDeclStrongDefinition(cast<VarDecl>(D), CodeGenOpts.NoCommon))
+      !isVarDeclStrongDefinition(Context, cast<VarDecl>(D),
+                                 CodeGenOpts.NoCommon))
     return llvm::GlobalVariable::CommonLinkage;
 
   // selectany symbols are externally visible, so use weak instead of

Added: cfe/trunk/test/CodeGen/ms-align-tentative.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/ms-align-tentative.c?rev=214828&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/ms-align-tentative.c (added)
+++ cfe/trunk/test/CodeGen/ms-align-tentative.c Mon Aug  4 19:01:13 2014
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -triple i386-pc-win32 %s -emit-llvm -fms-compatibility -o - | FileCheck %s
+
+char __declspec(align(8192)) x;
+// CHECK-DAG: @x = global i8 0, align 8192
+
+typedef char __declspec(align(8192)) T;
+T y;
+// CHECK-DAG: @y = global i8 0, align 8192
+
+T __declspec(align(8192)) z;
+// CHECK-DAG: @z = global i8 0, align 8192
+
+int __declspec(align(16)) redef;
+int __declspec(align(32)) redef = 8;
+// CHECK-DAG: @redef = global i32 8, align 32