Index: clang/lib/AST/StmtProfile.cpp
===================================================================
--- clang/lib/AST/StmtProfile.cpp
+++ clang/lib/AST/StmtProfile.cpp
@@ -1535,8 +1535,8 @@
     return Stmt::BinaryOperatorClass;
 
   case OO_Spaceship:
-    // FIXME: Update this once we support <=> expressions.
-    llvm_unreachable("<=> expressions not supported yet");
+    BinaryOp = BO_Cmp;
+    return Stmt::BinaryOperatorClass;
 
   case OO_AmpAmp:
     BinaryOp = BO_LAnd;
Index: clang/test/SemaCXX/cxx2a-three-way-comparison.cpp
===================================================================
--- clang/test/SemaCXX/cxx2a-three-way-comparison.cpp
+++ clang/test/SemaCXX/cxx2a-three-way-comparison.cpp
@@ -22,3 +22,5 @@
 };
 
 int &r = B().operator<=>(0);
+
+template<typename T> void f(T x) { decltype(x <=> x) v; }