Fix the emission of ARC ivar layouts in the non-fragile Mac runtime.

My previous change in this area accidentally broke the rule when
InstanceBegin was not a multiple of the word size.

llvm-svn: 251666

1 files changed, 11 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 44c9a90c76c..e3cba265efa 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -2081,7 +2081,7 @@ llvm::Constant *CGObjCCommonMac::BuildGCBlockLayout(CodeGenModule &CGM,
 
   llvm::SmallVector<unsigned char, 32> buffer;
   llvm::Constant *C = builder.buildBitmap(*this, buffer);
-  if (CGM.getLangOpts().ObjCGCBitmapPrint) {
+  if (CGM.getLangOpts().ObjCGCBitmapPrint && !buffer.empty()) {
     printf("\n block variable layout for block: ");
     builder.dump(buffer);
   }
@@ -4861,6 +4861,9 @@ llvm::Constant *IvarLayoutBuilder::buildBitmap(CGObjCCommonMac &CGObjC,
     endOfLastScanInWords = endOfScanInWords;
   }
 
+  if (buffer.empty())
+    return llvm::ConstantPointerNull::get(CGM.Int8PtrTy);
+
   // For GC layouts, emit a skip to the end of the allocation so that we
   // have precise information about the entire thing.  This isn't useful
   // or necessary for the ARC-style layout strings.
@@ -4922,9 +4925,9 @@ CGObjCCommonMac::BuildIvarLayout(const ObjCImplementationDecl *OMD,
   // up.
   //
   // ARC layout strings only include the class's ivars.  In non-fragile
-  // runtimes, that means starting at InstanceStart.  In fragile runtimes,
-  // there's no InstanceStart, so it means starting at the end of the
-  // superclass, rounded up to word alignment.
+  // runtimes, that means starting at InstanceStart, rounded up to word
+  // alignment.  In fragile runtimes, there's no InstanceStart, so it means
+  // starting at the end of the superclass, rounded up to word alignment.
   //
   // MRC weak layout strings follow the ARC style.
   CharUnits baseOffset;
@@ -4938,10 +4941,12 @@ CGObjCCommonMac::BuildIvarLayout(const ObjCImplementationDecl *OMD,
     } else if (auto superClass = OI->getSuperClass()) {
       auto startOffset =
         CGM.getContext().getASTObjCInterfaceLayout(superClass).getSize();
-      baseOffset = startOffset.RoundUpToAlignment(CGM.getPointerAlign());
+      baseOffset = startOffset;
     } else {
       baseOffset = CharUnits::Zero();
     }
+
+    baseOffset = baseOffset.RoundUpToAlignment(CGM.getPointerAlign());
   }
   else {
     CGM.getContext().DeepCollectObjCIvars(OI, true, ivars);
@@ -4965,7 +4970,7 @@ CGObjCCommonMac::BuildIvarLayout(const ObjCImplementationDecl *OMD,
   llvm::SmallVector<unsigned char, 4> buffer;
   llvm::Constant *C = builder.buildBitmap(*this, buffer);
   
-   if (CGM.getLangOpts().ObjCGCBitmapPrint) {
+   if (CGM.getLangOpts().ObjCGCBitmapPrint && !buffer.empty()) {
     printf("\n%s ivar layout for class '%s': ",
            ForStrongLayout ? "strong" : "weak",
            OMD->getClassInterface()->getName().str().c_str());