Add partial support for using anonymous bitfields (e.g., int : 0) to enforce
alignment. This fixes cases where the anonymous bitfield is followed by a
non-bitfield member. E.g.,
struct t4
{
int foo : 1;
long : 0;
char bar;
};
Part of rdar://9859156
llvm-svn: 136858
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index bb5b334..19a762c 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1348,6 +1348,13 @@
}
LastFD = FD;
}
+ else if (Context.Target.useZeroLengthBitfieldAlignment() &&
+ !Context.Target.useBitFieldTypeAlignment()) {
+ FieldDecl *FD = (*Field);
+ if (Context.ZeroBitfieldFollowsBitfield(FD, LastFD))
+ ZeroLengthBitfield = FD;
+ LastFD = FD;
+ }
LayoutField(*Field);
}
if (IsMsStruct && RemainingInAlignment &&
@@ -1442,7 +1449,7 @@
// This check is needed for 'long long' in -m32 mode.
if (IsMsStruct && (TypeSize > FieldAlign))
FieldAlign = TypeSize;
-
+
if (ZeroLengthBitfield) {
// If a zero-length bitfield is inserted after a bitfield,
// and the alignment of the zero-length bitfield is
@@ -1559,17 +1566,29 @@
Context.getTypeInfoInChars(D->getType());
FieldSize = FieldInfo.first;
FieldAlign = FieldInfo.second;
-
+
if (ZeroLengthBitfield) {
- // If a zero-length bitfield is inserted after a bitfield,
- // and the alignment of the zero-length bitfield is
- // greater than the member that follows it, `bar', `bar'
- // will be aligned as the type of the zero-length bitfield.
- std::pair<CharUnits, CharUnits> FieldInfo =
- Context.getTypeInfoInChars(ZeroLengthBitfield->getType());
- CharUnits ZeroLengthBitfieldAlignment = FieldInfo.second;
- if (ZeroLengthBitfieldAlignment > FieldAlign)
- FieldAlign = ZeroLengthBitfieldAlignment;
+ CharUnits ZeroLengthBitfieldBoundary =
+ Context.toCharUnitsFromBits(
+ Context.Target.getZeroLengthBitfieldBoundary());
+ if (ZeroLengthBitfieldBoundary == CharUnits::Zero()) {
+ // If a zero-length bitfield is inserted after a bitfield,
+ // and the alignment of the zero-length bitfield is
+ // greater than the member that follows it, `bar', `bar'
+ // will be aligned as the type of the zero-length bitfield.
+ std::pair<CharUnits, CharUnits> FieldInfo =
+ Context.getTypeInfoInChars(ZeroLengthBitfield->getType());
+ CharUnits ZeroLengthBitfieldAlignment = FieldInfo.second;
+ if (ZeroLengthBitfieldAlignment > FieldAlign)
+ FieldAlign = ZeroLengthBitfieldAlignment;
+ }
+ else if (ZeroLengthBitfieldBoundary > FieldAlign) {
+ // Align 'bar' based on a fixed alignment specified by the target.
+ assert (Context.Target.useZeroLengthBitfieldAlignment() &&
+ "ZeroLengthBitfieldBoundary should only be used in conjunction"
+ "with useZeroLengthBitfieldAlignment.");
+ FieldAlign = ZeroLengthBitfieldBoundary;
+ }
ZeroLengthBitfield = 0;
}