objective-c blocks: Consider padding due to alignment

after the fixed size block header when generating
captured block variable info. // rdar://12773256

llvm-svn: 169285

3 files changed, 25 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index 1d8b326d207..d181da2de66 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -428,7 +428,11 @@ static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
   // to get reproducible results.  There should probably be an
   // llvm::array_pod_stable_sort.
   std::stable_sort(layout.begin(), layout.end());
-
+  
+  // Needed for blocks layout info.
+  info.BlockHeaderForcedGapOffset = info.BlockSize;
+  info.BlockHeaderForcedGapSize = CharUnits::Zero();
+  
   CharUnits &blockSize = info.BlockSize;
   info.BlockAlign = std::max(maxFieldAlign, info.BlockAlign);
 
@@ -469,17 +473,22 @@ static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
         endAlign = getLowBit(blockSize);
 
         // ...until we get to the alignment of the maximum field.
-        if (endAlign >= maxFieldAlign)
+        if (endAlign >= maxFieldAlign) {
+          if (li == first) {
+            // No user field was appended. So, a gap was added.
+            // Save total gap size for use in block layout bit map.
+            info.BlockHeaderForcedGapSize = li->Size;
+          }
           break;
+        }
       }
-
       // Don't re-append everything we just appended.
       layout.erase(first, li);
     }
   }
 
   assert(endAlign == getLowBit(blockSize));
-
+  
   // At this point, we just have to add padding if the end align still
   // isn't aligned right.
   if (endAlign < maxFieldAlign) {
@@ -494,7 +503,6 @@ static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
 
   assert(endAlign >= maxFieldAlign);
   assert(endAlign == getLowBit(blockSize));
-
   // Slam everything else on now.  This works because they have
   // strictly decreasing alignment and we expect that size is always a
   // multiple of alignment.
diff --git a/clang/lib/CodeGen/CGBlocks.h b/clang/lib/CodeGen/CGBlocks.h
index e63d4b6b1f0..0e40478fad7 100644
--- a/clang/lib/CodeGen/CGBlocks.h
+++ b/clang/lib/CodeGen/CGBlocks.h
@@ -211,6 +211,14 @@ public:
   const BlockExpr *BlockExpression;
   CharUnits BlockSize;
   CharUnits BlockAlign;
+  
+  // Offset of the gap caused by block header having a smaller
+  // alignment than the alignment of the block descriptor. This
+  // is the gap offset before the first capturued field.
+  CharUnits BlockHeaderForcedGapOffset;
+  // Gap size caused by aligning first field after block header.
+  // This could be zero if no forced alignment is required.
+  CharUnits BlockHeaderForcedGapSize;
 
   /// An instruction which dominates the full-expression that the
   /// block is inside.
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index f4b42bb9b7d..d84875bfd51 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -2424,7 +2424,10 @@ llvm::Constant *CGObjCCommonMac::BuildRCBlockLayout(CodeGenModule &CGM,
   
   // Ignore the optional 'this' capture: C++ objects are not assumed
   // to be GC'ed.
-  
+  if (blockInfo.BlockHeaderForcedGapSize != CharUnits::Zero())
+    UpdateRunSkipBlockVars(false, Qualifiers::OCL_None,
+                           blockInfo.BlockHeaderForcedGapOffset,
+                           blockInfo.BlockHeaderForcedGapSize);
   // Walk the captured variables.
   for (BlockDecl::capture_const_iterator ci = blockDecl->capture_begin(),
        ce = blockDecl->capture_end(); ci != ce; ++ci) {