[ms-abi] Small Change to pack+alignment interaction.

This patch makes a small behavioral change to the interaction between 
pack and alignment.  Specifically it makes __declspec(align()) on a 
field change that field's alignment without respect to pack but the 
alignment change to the record alignment as a whole still obeys pack.

llvm-svn: 199172

1 files changed, 7 insertions, 4 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 6b3a431da21..9183e5c66f2 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2186,6 +2186,9 @@ MicrosoftRecordLayoutBuilder::getAdjustedElementInfo(
         Context.getTypeInfoInChars(FD->getType());
     if (FD->isBitField() && FD->getMaxAlignment() != 0)
       Info.Alignment = std::max(Info.Alignment, FieldRequiredAlignment);
+    // Respect pragma pack.
+    if (!MaxFieldAlignment.isZero())
+      Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment);
   }
   // Respect packed field attribute.
   if (FD->hasAttr<PackedAttr>())
@@ -2197,12 +2200,12 @@ MicrosoftRecordLayoutBuilder::getAdjustedElementInfo(
     // Capture required alignment as a side-effect.
     RequiredAlignment = std::max(RequiredAlignment, FieldRequiredAlignment);
   }
-  // Respect pragma pack.
-  if (!MaxFieldAlignment.isZero())
-    Info.Alignment = std::min(Info.Alignment, MaxFieldAlignment);
   // TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
-  if (!(FD->isBitField() && IsUnion))
+  if (!(FD->isBitField() && IsUnion)) {
     Alignment = std::max(Alignment, Info.Alignment);
+    if (!MaxFieldAlignment.isZero())
+      Alignment = std::min(Alignment, MaxFieldAlignment);
+  }
   return Info;
 }