Opting out of Clang 16 ABI Changes for AIX and z/OS

There is already a GCC compatibility gap on AIX, & GCC compatibility is
not a concern on z/OS. GCC compatibility is not sufficient motivation
for breaking ABI on AIX and z/OS. This opts out of changes introduced in
https://reviews.llvm.org/D119051. For AIX only, also opt out of D117616
(which z/OS had picked up at the time ABI stabilization occurred).

Differential Revision: https://reviews.llvm.org/D142358

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f7a68a6..7d356e5 100644 (file)
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -838,13 +838,14 @@ ABI Changes in Clang
 
 - GCC doesn't pack non-POD members in packed structs unless the packed
   attribute is also specified on the member. Clang historically did perform
-  such packing. Clang now matches the gcc behavior (except on Darwin and PS4).
+  such packing. Clang now matches the gcc behavior
+  (except on Darwin, PS4 and AIX).
   You can switch back to the old ABI behavior with the flag:
   ``-fclang-abi-compat=15.0``.
 - GCC allows POD types to have defaulted special members. Clang historically
   classified such types as non-POD (for the purposes of Itanium ABI). Clang now
-  matches the gcc behavior (except on Darwin and PS4). You can switch back to
-  the old ABI behavior with the flag: ``-fclang-abi-compat=15.0``.
+  matches the gcc behavior (except on Darwin, PS4, AIX and z/OS). You can switch
+  back to the old ABI behavior with the flag: ``-fclang-abi-compat=15.0``.
 
 OpenMP Support in Clang
 -----------------------

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index da27f73..2f54639 100644 (file)
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1968,7 +1968,8 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D,
                                  FieldClass->hasAttr<PackedAttr>() ||
                                  Context.getLangOpts().getClangABICompat() <=
                                      LangOptions::ClangABI::Ver15 ||
-                                 Target.isPS() || Target.isOSDarwin())) ||
+                                 Target.isPS() || Target.isOSDarwin() ||
+                                 Target.isOSAIX())) ||
                      D->hasAttr<PackedAttr>();
 
   // When used as part of a typedef, or together with a 'packed' attribute, the

diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
index a1b1f91..fd372cb 100644 (file)
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -773,6 +773,10 @@ public:
   }
 
   bool defaultsToAIXPowerAlignment() const override { return true; }
+
+  bool areDefaultedSMFStillPOD(const LangOptions &) const override {
+    return false;
+  }
 };
 
 // z/OS target
@@ -831,6 +835,10 @@ public:
     this->UseLeadingZeroLengthBitfield = false;
     this->ZeroLengthBitfieldBoundary = 32;
   }
+
+  bool areDefaultedSMFStillPOD(const LangOptions &) const override {
+    return false;
+  }
 };
 
 void addWindowsDefines(const llvm::Triple &Triple, const LangOptions &Opts,

diff --git a/clang/test/SemaCXX/class-layout.cpp b/clang/test/SemaCXX/class-layout.cpp
index 3d710dc..3ccd0ad 100644 (file)
--- a/clang/test/SemaCXX/class-layout.cpp
+++ b/clang/test/SemaCXX/class-layout.cpp
@@ -7,8 +7,17 @@
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=14 -DCLANG_ABI_COMPAT=14
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=15 -DCLANG_ABI_COMPAT=15
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=16 -DCLANG_ABI_COMPAT=16
+// RUN: %clang_cc1 -triple powerpc-ibm-aix7.3.0.0 %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -DCLANG_ABI_COMPAT=15
+// RUN: %clang_cc1 -triple powerpc-ibm-aix7.3.0.0 %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=15 -DCLANG_ABI_COMPAT=15
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix7.3.0.0 %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -DCLANG_ABI_COMPAT=15
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix7.3.0.0 %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=15 -DCLANG_ABI_COMPAT=15
+// RUN: %clang_cc1 -triple s390x-none-zos %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base
+// RUN: %clang_cc1 -triple s390x-none-zos %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=15 -DCLANG_ABI_COMPAT=15
+
 // expected-no-diagnostics
 
+#if !defined(__MVS__) && !defined(_AIX)
+
 #define SA(n, p) int a##n[(p) ? 1 : -1]
 
 struct A {
@@ -611,6 +620,8 @@ namespace PR37275 {
 #pragma pack(pop)
 }
 
+#endif // !defined(__MVS__) && !defined(__AIX__)
+
 namespace non_pod {
 struct t1 {
 protected:
@@ -670,11 +681,15 @@ struct t1 {
 struct t2 {
   t1 v1;
 } __attribute__((packed));
+#if (defined(CLANG_ABI_COMPAT) && CLANG_ABI_COMPAT <= 15) || !defined(__MVS__)
 _Static_assert(_Alignof(t2) == 1, "");
+#else
+_Static_assert(_Alignof(t2) == 4, "");
+#endif
 struct t3 : t1 {
   char c;
 };
-#if defined(CLANG_ABI_COMPAT) && CLANG_ABI_COMPAT <= 15
+#if (defined(CLANG_ABI_COMPAT) && CLANG_ABI_COMPAT <= 15) || defined(__MVS__)
 _Static_assert(sizeof(t3) == 8, "");
 #else
 _Static_assert(sizeof(t3) == 12, "");