From b63f779be4b076e530f9d2f79cdb1d09925356b5 Mon Sep 17 00:00:00 2001
From: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Date: Tue, 21 Apr 2015 17:26:18 +0000
Subject: [PATCH] Fix __alignof__ of global variables on SystemZ

SystemZ prefers to align all global variables to two bytes, which is
implemented by setting the TargetInfo member MinGlobalAlign.

However, for compatibility with existing compilers this should *not*
change the ABI alignment value as retrieved via __alignof__, which
it currently does.

This patch fixes the issue by having ASTContext::getDeclAlign ignore
the MinGlobalAlign setting in the ForAlignof case.

Since SystemZ is the only platform setting MinGlobalAlign, this should
cause no change for any other target.

llvm-svn: 235395
---
 clang/lib/AST/ASTContext.cpp       |  2 +-
 clang/test/CodeGen/align-systemz.c | 14 ++++++++++++++
 clang/test/Sema/align-systemz.c    | 17 +++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CodeGen/align-systemz.c
 create mode 100644 clang/test/Sema/align-systemz.c

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 899f8c5..c54a006 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1335,7 +1335,7 @@ CharUnits ASTContext::getDeclAlign(const Decl *D, bool ForAlignof) const {
       }
       Align = std::max(Align, getPreferredTypeAlign(T.getTypePtr()));
       if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
-        if (VD->hasGlobalStorage())
+        if (VD->hasGlobalStorage() && !ForAlignof)
           Align = std::max(Align, getTargetInfo().getMinGlobalAlign());
       }
     }
diff --git a/clang/test/CodeGen/align-systemz.c b/clang/test/CodeGen/align-systemz.c
new file mode 100644
index 0000000..277492c
--- /dev/null
+++ b/clang/test/CodeGen/align-systemz.c
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple s390x-linux-gnu -emit-llvm %s -o - | FileCheck %s
+
+// SystemZ prefers to align all global variables to two bytes.
+
+struct test {
+   signed char a;
+};
+
+char c;
+// CHECK-DAG: @c = common global i8 0, align 2
+
+struct test s;
+// CHECK-DAG: @s = common global %struct.test zeroinitializer, align 2
+
diff --git a/clang/test/Sema/align-systemz.c b/clang/test/Sema/align-systemz.c
new file mode 100644
index 0000000..6928549
--- /dev/null
+++ b/clang/test/Sema/align-systemz.c
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -triple s390x-linux-gnu -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+// SystemZ prefers to align all global variables to two bytes,
+// but this should *not* be reflected in the ABI alignment as
+// retrieved via __alignof__.
+
+struct test {
+  signed char a;
+};
+
+char c;
+struct test s;
+
+int chk1[__alignof__(c) == 1 ? 1 : -1];
+int chk2[__alignof__(s) == 1 ? 1 : -1];
+
-- 
2.7.4