[CodeGen][ObjC] Fix GNU's encoding of bit-field ivars.

According to the documentation, when encoding a bit-field, GNU runtime
needs its starting position in addition to its type and size.

https://gcc.gnu.org/onlinedocs/gcc/Type-encoding.html

Prior to r297702, the starting position information was not being
encoded, which is incorrect, and after r297702, an assertion started to
fail because an ObjCIvarDecl was being passed to a function expecting a
FieldDecl.

This commit moves LookupFieldBitOffset to ASTContext and uses the
function to encode the starting position of bit-fields.

llvm-svn: 306364

1 files changed, 13 insertions, 3 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index fabfdc9ef7e..a2ff176df11 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -5990,9 +5990,19 @@ static void EncodeBitField(const ASTContext *Ctx, std::string& S,
   // compatibility with GCC, although providing it breaks anything that
   // actually uses runtime introspection and wants to work on both runtimes...
   if (Ctx->getLangOpts().ObjCRuntime.isGNUFamily()) {
-    const RecordDecl *RD = FD->getParent();
-    const ASTRecordLayout &RL = Ctx->getASTRecordLayout(RD);
-    S += llvm::utostr(RL.getFieldOffset(FD->getFieldIndex()));
+    uint64_t Offset;
+
+    if (const auto *IVD = dyn_cast<ObjCIvarDecl>(FD)) {
+      Offset = Ctx->lookupFieldBitOffset(IVD->getContainingInterface(), nullptr,
+                                         IVD);
+    } else {
+      const RecordDecl *RD = FD->getParent();
+      const ASTRecordLayout &RL = Ctx->getASTRecordLayout(RD);
+      Offset = RL.getFieldOffset(FD->getFieldIndex());
+    }
+
+    S += llvm::utostr(Offset);
+
     if (const EnumType *ET = T->getAs<EnumType>())
       S += ObjCEncodingForEnumType(Ctx, ET);
     else {