Introduce f[no-]max-unknown-pointer-align=[number] option

to instruct the code generator to not enforce a higher alignment 
than the given number (of bytes) when accessing memory via an opaque 
pointer or reference. Patch reviewed by John McCall (with post-commit
review pending). rdar://16254558

llvm-svn: 214911

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 8496292..a200548 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -1399,8 +1399,13 @@ public:
 
   LValue MakeNaturalAlignAddrLValue(llvm::Value *V, QualType T) {
     CharUnits Alignment;
-    if (!T->isIncompleteType())
+    if (!T->isIncompleteType()) {
       Alignment = getContext().getTypeAlignInChars(T);
+      unsigned MaxAlign = getContext().getLangOpts().MaxTypeAlign;
+      if (MaxAlign && Alignment.getQuantity() > MaxAlign &&
+          !getContext().isAlignmentRequired(T))
+        Alignment = CharUnits::fromQuantity(MaxAlign);
+    }
     return LValue::MakeAddr(V, T, Alignment, getContext(),
                             CGM.getTBAAInfo(T));
   }