Diagnose when #pragma clang fp eval_method doesn't have a supported value.

Currently the compiler is crashing.

Differential Revision: https://reviews.llvm.org/D121380

Author: zahiraam

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1489,7 +1489,8 @@ def err_pragma_fp_invalid_argument : Error<
   "%select{"
   "'fast' or 'on' or 'off'|"
   "'on' or 'off'|"
-  "'ignore', 'maytrap' or 'strict'}2">;
+  "'ignore', 'maytrap' or 'strict'|"
+  "'source', 'double' or 'extended'}2">;
 
 def err_pragma_invalid_keyword : Error<
   "invalid argument; expected 'enable'%select{|, 'full'}0%select{|, 'assume_safety'}1 or 'disable'">;

clang/test/Sema/fp-eval-pragma.cpp

@@ -27,6 +27,16 @@ int foo2() {
   return 0;
 }
 
+void apply_pragma_with_wrong_value() {
+  // expected-error@+1{{unexpected argument 'value' to '#pragma clang fp eval_method'; expected 'source', 'double' or 'extended'}}
+#pragma clang fp eval_method(value)
+}
+
+int foo3() {
+  apply_pragma_with_wrong_value();
+  return 0;
+}
+
 void foo() {
   auto a = __FLT_EVAL_METHOD__;
   {