https://github.com/JonPsson1 created
https://github.com/llvm/llvm-project/pull/72886
The SystemZ ABI requires any global variable to be aligned to at least 2 bytes,
and therefore an external global Value with an opaque type should get this
alignment as well.
>From e9380e98527790aee19857b221b7b63d43a0ee87 Mon Sep 17 00:00:00 2001
From: Jonas Paulsson <pauls...@linux.ibm.com>
Date: Mon, 20 Nov 2023 12:29:33 +0100
Subject: [PATCH] [clang] Ensure minimial alignment of global vars of
incomplete type.
The SystemZ ABI requires any global variable to be aligned to at least 2
bytes, and therefore an external global Value with an opaque type should get
this alignment as well.
---
clang/lib/AST/ASTContext.cpp | 14 +++++++-----
clang/test/Driver/systemz-alignment.c | 32 +++++++++++++++++++++++++++
2 files changed, 40 insertions(+), 6 deletions(-)
create mode 100644 clang/test/Driver/systemz-alignment.c
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 1c893d008cb49f3..a7cee3b7ba2b0db 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1680,14 +1680,16 @@ CharUnits ASTContext::getDeclAlign(const Decl *D, bool
ForAlignof) const {
Align = std::max(Align, getPreferredTypeAlign(T.getTypePtr()));
if (BaseT.getQualifiers().hasUnaligned())
Align = Target->getCharWidth();
- if (const auto *VD = dyn_cast<VarDecl>(D)) {
- if (VD->hasGlobalStorage() && !ForAlignof) {
- uint64_t TypeSize = getTypeSize(T.getTypePtr());
- Align = std::max(Align, getTargetInfo().getMinGlobalAlign(TypeSize));
- }
- }
}
+ // Ensure miminum alignment for global variables.
+ if (const auto *VD = dyn_cast<VarDecl>(D))
+ if (VD->hasGlobalStorage() && !ForAlignof) {
+ uint64_t TypeSize =
+ !BaseT->isIncompleteType() ? getTypeSize(T.getTypePtr()) : 0;
+ Align = std::max(Align, getTargetInfo().getMinGlobalAlign(TypeSize));
+ }
+
// Fields can be subject to extra alignment constraints, like if
// the field is packed, the struct is packed, or the struct has a
// a max-field-alignment constraint (#pragma pack). So calculate
diff --git a/clang/test/Driver/systemz-alignment.c
b/clang/test/Driver/systemz-alignment.c
new file mode 100644
index 000000000000000..6f3b2bc38be3688
--- /dev/null
+++ b/clang/test/Driver/systemz-alignment.c
@@ -0,0 +1,32 @@
+// RUN: %clang --target=s390x-linux -S -emit-llvm -o - %s | FileCheck %s
+//
+// Test that a global variable with an incomplete type gets the minimum
+// alignment of 2 per the ABI if no alignment was specified by user.
+//
+// CHECK: @VarNoAl {{.*}} align 2
+// CHECK-NEXT: @VarExplAl1 {{.*}} align 1
+// CHECK-NEXT: @VarExplAl4 {{.*}} align 4
+
+// No alignemnt specified by user.
+struct incomplete_ty_noal;
+extern struct incomplete_ty_noal VarNoAl;
+struct incomplete_ty_noal *fun0 (void)
+{
+ return &VarNoAl;
+}
+
+// User-specified alignment of 1.
+struct incomplete_ty_al1;
+extern struct incomplete_ty_al1 __attribute__((aligned(1))) VarExplAl1;
+struct incomplete_ty_al1 *fun1 (void)
+{
+ return &VarExplAl1;
+}
+
+// User-specified alignment of 4.
+struct incomplete_ty_al4;
+extern struct incomplete_ty_al4 __attribute__((aligned(4))) VarExplAl4;
+struct incomplete_ty_al4 *fun2 (void)
+{
+ return &VarExplAl4;
+}
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