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-rw-r--r--lib/AST/RecordLayoutBuilder.cpp29
1 files changed, 28 insertions, 1 deletions
diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp
index a9d43dfa80c5..de38bc9b64dd 100644
--- a/lib/AST/RecordLayoutBuilder.cpp
+++ b/lib/AST/RecordLayoutBuilder.cpp
@@ -1751,7 +1751,34 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D,
QualType T = Context.getBaseElementType(D->getType());
if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
- if (TypeSize > FieldAlign)
+
+ if (!llvm::isPowerOf2_64(TypeSize.getQuantity())) {
+ assert(
+ !Context.getTargetInfo().getTriple().isWindowsMSVCEnvironment() &&
+ "Non PowerOf2 size in MSVC mode");
+ // Base types with sizes that aren't a power of two don't work
+ // with the layout rules for MS structs. This isn't an issue in
+ // MSVC itself since there are no such base data types there.
+ // On e.g. x86_32 mingw and linux, long double is 12 bytes though.
+ // Any structs involving that data type obviously can't be ABI
+ // compatible with MSVC regardless of how it is laid out.
+
+ // Since ms_struct can be mass enabled (via a pragma or via the
+ // -mms-bitfields command line parameter), this can trigger for
+ // structs that don't actually need MSVC compatibility, so we
+ // need to be able to sidestep the ms_struct layout for these types.
+
+ // Since the combination of -mms-bitfields together with structs
+ // like max_align_t (which contains a long double) for mingw is
+ // quite comon (and GCC handles it silently), just handle it
+ // silently there. For other targets that have ms_struct enabled
+ // (most probably via a pragma or attribute), trigger a diagnostic
+ // that defaults to an error.
+ if (!Context.getTargetInfo().getTriple().isWindowsGNUEnvironment())
+ Diag(D->getLocation(), diag::warn_npot_ms_struct);
+ }
+ if (TypeSize > FieldAlign &&
+ llvm::isPowerOf2_64(TypeSize.getQuantity()))
FieldAlign = TypeSize;
}
}