diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -5808,7 +5808,7 @@
            << OrigArg->getType() << OrigArg->getSourceRange();
 
   // If this is an implicit conversion from float -> float, double, or
-  // long double, remove it.
+  // long double, or half -> half, float, double, or long double, remove it.
   if (ImplicitCastExpr *Cast = dyn_cast<ImplicitCastExpr>(OrigArg)) {
     // Only remove standard FloatCasts, leaving other casts inplace
     if (Cast->getCastKind() == CK_FloatingCast) {
@@ -5823,6 +5823,18 @@
         Cast->setSubExpr(nullptr);
         TheCall->setArg(NumArgs-1, CastArg);
       }
+
+      if (CastArg->getType()->isSpecificBuiltinType(BuiltinType::Half)) {
+        assert(
+            (Cast->getType()->isSpecificBuiltinType(BuiltinType::Double) ||
+             Cast->getType()->isSpecificBuiltinType(BuiltinType::Float) ||
+             Cast->getType()->isSpecificBuiltinType(BuiltinType::Half) ||
+             Cast->getType()->isSpecificBuiltinType(BuiltinType::LongDouble)) &&
+            "promotion from half to either half, float, double, or long double "
+            "is the only expected cast here");
+        Cast->setSubExpr(nullptr);
+        TheCall->setArg(NumArgs-1, CastArg);
+      }
     }
   }