[CIR] Add a flag to disable CIR emission for default cxx methods

This allows us to test analysis without having to CIR codegen
compiler generated code.

Author: bcardosolopes

clang/include/clang/Driver/Options.td

@@ -2179,6 +2179,10 @@ def clangir_disable_verifier : Flag<["-"], "clangir-disable-verifier">,
   Flags<[CoreOption, CC1Option]>,
   HelpText<"ClangIR: Disable MLIR module verifier">,
   MarshallingInfoFlag<FrontendOpts<"ClangIRDisableCIRVerifier">>;
+def clangir_disable_emit_cxx_default : Flag<["-"], "clangir-disable-emit-cxx-default">,
+  Flags<[CoreOption, CC1Option]>,
+  HelpText<"ClangIR: Disable emission of c++ default (compiler implemented) methods.">,
+  MarshallingInfoFlag<FrontendOpts<"ClangIRDisableEmitCXXDefault">>;
 def clangir_verify_diagnostics : Flag<["-"], "clangir-verify-diagnostics">,
   Flags<[CoreOption, CC1Option]>,
   HelpText<"ClangIR: Enable diagnostic verification in MLIR, similar to clang's -verify">,

clang/include/clang/Frontend/FrontendOptions.h

@@ -361,6 +361,9 @@ class FrontendOptions {
   /// Disable Clang IR (CIR) verifier
   unsigned ClangIRDisableCIRVerifier : 1;
 
+  /// Disable ClangIR emission for CXX default (compiler generated methods).
+  unsigned ClangIRDisableEmitCXXDefault : 1;
+
   /// Enable diagnostic verification for CIR
   unsigned ClangIRVerifyDiags : 1;
 
@@ -537,8 +540,8 @@ class FrontendOptions {
         IncludeTimestamps(true), UseTemporary(true),
         AllowPCMWithCompilerErrors(false), ModulesShareFileManager(true),
         UseClangIRPipeline(false), ClangIRDisablePasses(false),
-        ClangIRDisableCIRVerifier(false), ClangIRLifetimeCheck(false),
-        TimeTraceGranularity(500) {}
+        ClangIRDisableCIRVerifier(false), ClangIRDisableEmitCXXDefault(false),
+        ClangIRLifetimeCheck(false), TimeTraceGranularity(500) {}
 
   /// getInputKindForExtension - Return the appropriate input kind for a file
   /// extension. For example, "c" would return Language::C.

clang/lib/CIR/FrontendAction/CIRGenAction.cpp

@@ -214,7 +214,8 @@ class CIRGenConsumer : public clang::ASTConsumer {
         }
 
         // Emit remaining defaulted C++ methods
-        gen->buildDefaultMethods();
+        if (!feOptions.ClangIRDisableEmitCXXDefault)
+          gen->buildDefaultMethods();
 
         // FIXME: we cannot roundtrip prettyForm=true right now.
         mlir::OpPrintingFlags flags;

clang/lib/Frontend/CompilerInvocation.cpp

@@ -2821,6 +2821,9 @@ static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   if (Args.hasArg(OPT_clangir_disable_verifier))
     Opts.ClangIRDisableCIRVerifier = true;
 
+  if (Args.hasArg(OPT_clangir_disable_emit_cxx_default))
+    Opts.ClangIRDisableEmitCXXDefault = true;
+
   if (Args.hasArg(OPT_clangir_verify_diagnostics))
     Opts.ClangIRVerifyDiags = true;
 

clang/test/CIR/CodeGen/assign-operator.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -std=c++17 -mconstructor-aliases -triple x86_64-unknown-linux-gnu -fclangir-enable -emit-cir %s -o - | FileCheck %s
+// RUN: %clang_cc1 -std=c++17 -mconstructor-aliases -triple x86_64-unknown-linux-gnu -fclangir-enable -emit-cir -clangir-disable-emit-cxx-default %s -o - | FileCheck %s --check-prefix=DISABLE
 
 int strlen(char const *);
 
@@ -24,6 +25,9 @@ struct String {
   // CHECK:   cir.return
   // CHECK: }
 
+  // DISABLE: cir.func linkonce_odr @_ZN10StringViewC2ERK6String
+  // DISABLE-NEXT:   %0 = cir.alloca !cir.ptr<!22struct2EStringView22>, cir.ptr <!cir.ptr<!22struct2EStringView22>>, ["this", init] {alignment = 8 : i64}
+
   // StringView::operator=(StringView&&)
   //
   // CHECK: cir.func linkonce_odr @_ZN10StringViewaSEOS_
@@ -42,6 +46,9 @@ struct String {
   // CHECK:   %8 = cir.load %2 : cir.ptr <!cir.ptr<!22struct2EStringView22>>
   // CHECK:   cir.return %8 : !cir.ptr<!22struct2EStringView22>
   // CHECK: }
+
+  // DISABLE: cir.func @_ZN10StringViewaSEOS_
+  // DISABLE-NEXT: cir.func @main()
 };
 
 struct StringView {