diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -13639,14 +13639,6 @@
   if (ResultTy.isNull() || LHS.isInvalid() || RHS.isInvalid())
     return ExprError();
 
-  // The LHS is not converted to the result type for fixed-point compound
-  // assignment as the common type is computed on demand. Reset the CompLHSTy
-  // to the LHS type we would have gotten after unary conversions.
-  if (!CompLHSTy.isNull() &&
-      (LHS.get()->getType()->isFixedPointType() ||
-       RHS.get()->getType()->isFixedPointType()))
-    CompLHSTy = UsualUnaryConversions(LHS.get()).get()->getType();
-
   if (ResultTy->isRealFloatingType() &&
       (getLangOpts().getFPRoundingMode() != RoundingMode::NearestTiesToEven ||
        getLangOpts().getFPExceptionMode() != LangOptions::FPE_Ignore))
@@ -13705,6 +13697,12 @@
     OK = LHS.get()->getObjectKind();
   }
 
+  // The LHS is not converted to the result type for fixed-point compound
+  // assignment as the common type is computed on demand. Reset the CompLHSTy
+  // to the LHS type we would have gotten after unary conversions.
+  if (CompResultTy->isFixedPointType())
+    CompLHSTy = UsualUnaryConversions(LHS.get()).get()->getType();
+
   if (ConvertHalfVec)
     return convertHalfVecBinOp(*this, LHS, RHS, Opc, ResultTy, VK, OK, true,
                                OpLoc, CurFPFeatures);