[CIR] Added missing argument handling to clang toolchain (#1781)

We were missing argument handling for `-fclangir-idiom-recognizer` on
its own, and were not propagating `-fclangir-lib-opt` for the clang
toolchain.

Author: tommymcm

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5099,12 +5099,18 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (Args.hasArg(options::OPT_fclangir_mem2reg))
     CmdArgs.push_back("-fclangir-mem2reg");
 
+  bool enable_idiom_recognizer =
+      Args.hasArg(options::OPT_fclangir_idiom_recognizer,
+                  options::OPT_fclangir_idiom_recognizer_EQ);
+  if (enable_idiom_recognizer)
+    CmdArgs.push_back("-fclangir-idiom-recognizer");
+
   // ClangIR lib opt requires idiom recognizer.
   if (Args.hasArg(options::OPT_fclangir_lib_opt,
                   options::OPT_fclangir_lib_opt_EQ)) {
-    if (!Args.hasArg(options::OPT_fclangir_idiom_recognizer,
-                     options::OPT_fclangir_idiom_recognizer_EQ))
+    if (!enable_idiom_recognizer)
       CmdArgs.push_back("-fclangir-idiom-recognizer");
+    CmdArgs.push_back("-fclangir-lib-opt");
   }
 
   if (Args.hasArg(options::OPT_fclangir_analysis_only)) {

clang/test/CIR/Driver/idiom-recognizer.cpp

@@ -0,0 +1,2 @@
+// RUN: %clang %s -fclangir-idiom-recognizer -### -c %s 2>&1 | FileCheck --check-prefix=ENABLE %s
+// ENABLE: "-fclangir-idiom-recognizer"

clang/test/CIR/Driver/lib-opt.cpp

@@ -0,0 +1,3 @@
+// RUN: %clang %s -fclangir-lib-opt -### -c %s 2>&1 | FileCheck --check-prefix=ENABLE %s
+// ENABLE: "-fclangir-lib-opt"
+// ENABLE: "-fclangir-idiom-recognizer"