Fix the field count in interface record layout (it was incorrectly

compensating for super classes). This was making the reported class
sizes for empty classes very, very wrong.
 - Also, we now report the size info for an empty class like gcc (as
   the offset of the start, not as 0, 0).

 - Add a few more test cases we were mishandling before (padding bit
   field at end of struct, for example).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@70938 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 57 insertions, 17 deletions

diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index a9f13c9518..a947fea95a 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -713,10 +713,6 @@ ASTContext::getObjCLayout(const ObjCInterfaceDecl *D,
 
   ASTRecordLayout *NewEntry = NULL;
   if (ObjCInterfaceDecl *SD = D->getSuperClass()) {
-    // FIXME: This increment of FieldCount is wrong, we don't actually
-    // count the super class as a member (see the field index passed
-    // to LayoutField below).
-    FieldCount++;
     const ASTRecordLayout &SL = getASTObjCInterfaceLayout(SD);
     unsigned Alignment = SL.getAlignment();
     uint64_t Size = SL.getSize();
@@ -729,8 +725,6 @@ ASTContext::getObjCLayout(const ObjCInterfaceDecl *D,
 
     ObjCLayouts[Key] = NewEntry = new ASTRecordLayout(Size, Alignment);
     NewEntry->InitializeLayout(FieldCount);
-    // Super class is at the beginning of the layout.
-    NewEntry->SetFieldOffset(0, 0);
   } else {
     ObjCLayouts[Key] = NewEntry = new ASTRecordLayout();
     NewEntry->InitializeLayout(FieldCount);
diff --git a/lib/CodeGen/CGObjCMac.cpp b/lib/CodeGen/CGObjCMac.cpp
index 1a1ef83123..1f58389ab8 100644
--- a/lib/CodeGen/CGObjCMac.cpp
+++ b/lib/CodeGen/CGObjCMac.cpp
@@ -4222,13 +4222,14 @@ void CGObjCNonFragileABIMac::GetClassSizeInfo(const ObjCImplementationDecl *OID,
   const ASTRecordLayout &RL = 
     CGM.getContext().getASTObjCImplementationLayout(OID);
   
-  if (!RL.getFieldCount()) {
-    InstanceStart = InstanceSize = 0;
-    return;
-  }
-
-  InstanceStart = RL.getFieldOffset(0) / 8;
+  // InstanceSize is really instance end.
   InstanceSize = llvm::RoundUpToAlignment(RL.getNextOffset(), 8) / 8;
+
+  // If there are no fields, the start is the same as the end.
+  if (!RL.getFieldCount())
+    InstanceStart = InstanceSize;
+  else
+    InstanceStart = RL.getFieldOffset(0) / 8;
 }
 
 void CGObjCNonFragileABIMac::GenerateClass(const ObjCImplementationDecl *ID) {
diff --git a/test/CodeGenObjC/interface-layout-64.m b/test/CodeGenObjC/interface-layout-64.m
index ee01ac6bb6..db860e8518 100644
--- a/test/CodeGenObjC/interface-layout-64.m
+++ b/test/CodeGenObjC/interface-layout-64.m
@@ -1,17 +1,36 @@
-// RUN: clang-cc -triple x86_64-apple-darwin9 -emit-llvm -o %t %s &&
+// RUN: clang-cc -fobjc-tight-layout -triple x86_64-apple-darwin9 -emit-llvm -o %t %s &&
 // RUNX: llvm-gcc -m64 -emit-llvm -S -o %t %s &&
 
 // RUN: grep '@"OBJC_IVAR_$_I3._iv2" = global i64 8, section "__DATA, __objc_const", align 8' %t &&
 // RUN: grep '@"OBJC_IVAR_$_I3._iv3" = global i64 12, section "__DATA, __objc_const", align 8' %t &&
-// RUN: grep '@"OBJC_IVAR_$_I4._iv4" = global i64 16, section "__DATA, __objc_const", align 8' %t &&
-// RUN: grep '@"OBJC_IVAR_$_I5._iv5" = global i64 24, section "__DATA, __objc_const", align 8' %t &&
-// RUN: grep '@"OBJC_IVAR_$_I5._iv6_synth" = global i64 28, section "__DATA, __objc_const", align 8' %t &&
-// RUN: grep '@"OBJC_IVAR_$_I5._iv7_synth" = global i64 32, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I4._iv4" = global i64 13, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I5._iv5" = global i64 14, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I5._iv6_synth" = global i64 16, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I5._iv7_synth" = global i64 20, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I6.iv0" = global i64 0, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I8.b" = global i64 8, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I9.iv0" = global i64 0, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I10.iv1" = global i64 4, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '@"OBJC_IVAR_$_I12.iv2" = global i64 8, section "__DATA, __objc_const", align 8' %t &&
+// RUN: grep '_OBJC_CLASS_RO_$_I3" = internal global .* { i32 0, i32 8, i32 13, .*' %t &&
+// RUN: grep '_OBJC_CLASS_RO_$_I4" = internal global .* { i32 0, i32 13, i32 14, .*' %t &&
+// RUN: grep '_OBJC_CLASS_RO_$_I5" = internal global .* { i32 0, i32 14, i32 24, .*' %t &&
 // RUN: grep '_OBJC_CLASS_RO_$_I6" = internal global .* { i32 2, i32 0, i32 1, .*' %t &&
 // RUN: grep '_OBJC_CLASS_RO_$_I8" = internal global .* { i32 0, i32 8, i32 16, .*' %t &&
+// RUN: grep '_OBJC_CLASS_RO_$_I9" = internal global .* { i32 2, i32 0, i32 4, .*' %t &&
+// RUN: grep '_OBJC_CLASS_RO_$_I10" = internal global .* { i32 0, i32 4, i32 5, .*' %t &&
+// RUN: grep '_OBJC_CLASS_RO_$_I11" = internal global .* { i32 0, i32 5, i32 5, .*' %t &&
+// RUN: grep '_OBJC_CLASS_RO_$_I12" = internal global .* { i32 0, i32 8, i32 12, .*' %t &&
 
 // RUN: true
 
+/*
+  Compare to:
+    gcc -m64 -S -o - interface-layout-64.m | grep '^_OBJC_IVAR_$_*.*' -A 1
+  and 
+    gcc -m64 -S -o - interface-layout-64.m | grep '^l.*_CLASS_RO_$_I[0-9]*' -A 3
+ */
+
 struct s0 {
   double x;
 };
@@ -77,3 +96,29 @@ struct s0 {
 @implementation I8
 @end
 
+// Padding bit-fields
+@interface I9 {
+  unsigned iv0 : 2;
+  unsigned : 0;
+}
+@end
+@implementation I9
+@end
+@interface I10 : I9 {
+  unsigned iv1 : 2;
+}
+@end
+@implementation I10
+@end
+
+// Empty structures
+@interface I11 : I10
+@end
+@implementation I11
+@end
+@interface I12 : I11 {
+  unsigned iv2;
+}
+@end
+@implementation I12
+@end