Use external layout information to layout bit-fields for MS ABI.
Patch by Aleksandr Urakov!
Differential Revision: https://reviews.llvm.org/D49227
llvm-svn: 337047
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 988b88b..b4b09c7c 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2677,7 +2677,7 @@
// Check to see if this bitfield fits into an existing allocation. Note:
// MSVC refuses to pack bitfields of formal types with different sizes
// into the same allocation.
- if (!IsUnion && LastFieldIsNonZeroWidthBitfield &&
+ if (!UseExternalLayout && !IsUnion && LastFieldIsNonZeroWidthBitfield &&
CurrentBitfieldSize == Info.Size && Width <= RemainingBitsInField) {
placeFieldAtBitOffset(Context.toBits(Size) - RemainingBitsInField);
RemainingBitsInField -= Width;
@@ -2689,6 +2689,14 @@
placeFieldAtOffset(CharUnits::Zero());
Size = std::max(Size, Info.Size);
// TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
+ } else if (UseExternalLayout) {
+ auto FieldBitOffset = External.getExternalFieldOffset(FD);
+ placeFieldAtBitOffset(FieldBitOffset);
+ auto NewSize = Context.toCharUnitsFromBits(
+ llvm::alignTo(FieldBitOffset + Width, Context.getCharWidth()));
+ assert(NewSize >= Size && "bit field offset already allocated");
+ Size = NewSize;
+ Alignment = std::max(Alignment, Info.Alignment);
} else {
// Allocate a new block of memory and place the bitfield in it.
CharUnits FieldOffset = Size.alignTo(Info.Alignment);