[RecordLayout] Don't align to non-power-of-2 sizes when using -mms-bitfields
When targeting GNU/MinGW for i386, the size of the "long double" data
type is 12 bytes (while it is 8 bytes in MSVC). When building
with -mms-bitfields to have struct layouts match MSVC, data types
are laid out in a struct with alignment according to their size.
However, this doesn't make sense for the long double type, since
it doesn't match MSVC at all, and aligning to a non-power-of-2
size triggers other asserts later.
This matches what GCC does, aligning a long double to 4 bytes
in structs on i386 even when -mms-bitfields is specified.
This fixes asserts when using the max_align_t data type when
building for MinGW/i386 with the -mms-bitfields flag.
Differential Revision: https://reviews.llvm.org/D43734
llvm-svn: 326173
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index dddacf2..a882c5e 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1752,7 +1752,12 @@
QualType T = Context.getBaseElementType(D->getType());
if (const BuiltinType *BTy = T->getAs<BuiltinType>()) {
CharUnits TypeSize = Context.getTypeSizeInChars(BTy);
- if (TypeSize > FieldAlign)
+ assert(
+ (llvm::isPowerOf2_64(TypeSize.getQuantity()) ||
+ Context.getTargetInfo().getTriple().isWindowsGNUEnvironment()) &&
+ "Non PowerOf2 size outside of GNU mode");
+ if (TypeSize > FieldAlign &&
+ llvm::isPowerOf2_64(TypeSize.getQuantity()))
FieldAlign = TypeSize;
}
}