Revert r264998 and r265035.

r303175 made changes to have __cxa_allocate_exception return a 16-byte
aligned pointer, so it's no longer necessary to specify a lower
alignment (8-bytes) for exception objects on Darwin.

rdar://problem/32363695

llvm-svn: 309308

2 files changed, 10 insertions, 9 deletions

diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
index 867810456b3..3919164bf9a 100644
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -127,13 +127,6 @@ public:
   /// is very similar to ELF's "protected";  Darwin requires a "weak"
   /// attribute on declarations that can be dynamically replaced.
   bool hasProtectedVisibility() const override { return false; }
-
-  unsigned getExnObjectAlignment() const override {
-    // The alignment of an exception object is 8-bytes for darwin since
-    // libc++abi doesn't declare _Unwind_Exception with __attribute__((aligned))
-    // and therefore doesn't guarantee 16-byte alignment.
-    return 64;
-  }
 };
 
 // DragonFlyBSD Target
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index de9fd042a9e..c1f892a3173 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -157,9 +157,17 @@ public:
                                Address Ptr, QualType ElementType,
                                const CXXDestructorDecl *Dtor) override;
 
+  /// Itanium says that an _Unwind_Exception has to be "double-word"
+  /// aligned (and thus the end of it is also so-aligned), meaning 16
+  /// bytes.  Of course, that was written for the actual Itanium,
+  /// which is a 64-bit platform.  Classically, the ABI doesn't really
+  /// specify the alignment on other platforms, but in practice
+  /// libUnwind declares the struct with __attribute__((aligned)), so
+  /// we assume that alignment here.  (It's generally 16 bytes, but
+  /// some targets overwrite it.)
   CharUnits getAlignmentOfExnObject() {
-    unsigned Align = CGM.getContext().getTargetInfo().getExnObjectAlignment();
-    return CGM.getContext().toCharUnitsFromBits(Align);
+    auto align = CGM.getContext().getTargetDefaultAlignForAttributeAligned();
+    return CGM.getContext().toCharUnitsFromBits(align);
   }
 
   void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) override;