Patch to issue error when target of MacOS and iOS 
does not support large load/store of atomic objects.
// rdar://13973577


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182781 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index f5e4b42..946d3df 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -8030,3 +8030,17 @@
          "ParmIndices lacks entry set by ParmVarDecl");
   return I->second;
 }
+
+bool ASTContext::AtomicUsesUnsupportedLibcall(const AtomicExpr *E) const {
+  const llvm::Triple &T = getTargetInfo().getTriple();
+  if (!T.isOSDarwin())
+    return false;
+
+  QualType AtomicTy = E->getPtr()->getType()->getPointeeType();
+  CharUnits sizeChars = getTypeSizeInChars(AtomicTy);
+  uint64_t Size = sizeChars.getQuantity();
+  CharUnits alignChars = getTypeAlignInChars(AtomicTy);
+  unsigned Align = alignChars.getQuantity();
+  unsigned MaxInlineWidthInBits = getTargetInfo().getMaxAtomicInlineWidth();
+  return (Size != Align || toBits(sizeChars) > MaxInlineWidthInBits);
+}
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index cdc546c..da24667 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -908,10 +908,18 @@
     SubExprs.push_back(TheCall->getArg(3)); // Weak
     break;
   }
+  
+  AtomicExpr *AE = new (Context) AtomicExpr(TheCall->getCallee()->getLocStart(),
+                                            SubExprs, ResultType, Op,
+                                            TheCall->getRParenLoc());
+  
+  if ((Op == AtomicExpr::AO__c11_atomic_load ||
+       (Op == AtomicExpr::AO__c11_atomic_store)) &&
+      Context.AtomicUsesUnsupportedLibcall(AE))
+    Diag(AE->getLocStart(), diag::err_atomic_load_store_uses_lib) <<
+    ((Op == AtomicExpr::AO__c11_atomic_load) ? 0 : 1);
 
-  return Owned(new (Context) AtomicExpr(TheCall->getCallee()->getLocStart(),
-                                        SubExprs, ResultType, Op,
-                                        TheCall->getRParenLoc()));
+  return Owned(AE);
 }