[clang] [CIR][NFC] Fix build warning in getCIRSourceLanguage (PR #155029)

[Andy Kaylor via cfe-commits]

https://github.com/andykaylor created https://github.com/llvm/llvm-project/pull/155029

The getCIRSourceLanguage wasn't returning a value if the source language was anything other than C or C++. This change updates that function to return a std::optional value and only adds the source language attribute if one was returned.

>From 0ff0ff0ff6e6452d4a692ab91f1baf711b49737b Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor at nvidia.com>
Date: Fri, 22 Aug 2025 14:06:50 -0700
Subject: [PATCH] [CIR][NFC] Fix build warning in getCIRSourceLanguage

The getCIRSourceLanguage wasn't returning a value if the source language
was anything other than C or C++. This change updates that function
to return a std::optional value and only adds the source language
attribute if one was returned.
---
 clang/lib/CIR/CodeGen/CIRGenModule.cpp | 11 +++++++----
 clang/lib/CIR/CodeGen/CIRGenModule.h   |  2 +-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
index 46bca51767c02..43554519ebd4d 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp
@@ -103,9 +103,11 @@ CIRGenModule::CIRGenModule(mlir::MLIRContext &mlirContext,
   PtrDiffTy =
       cir::IntType::get(&getMLIRContext(), sizeTypeSize, /*isSigned=*/true);
 
-  theModule->setAttr(
-      cir::CIRDialect::getSourceLanguageAttrName(),
-      cir::SourceLanguageAttr::get(&mlirContext, getCIRSourceLanguage()));
+  std::optional<cir::SourceLanguage> sourceLanguage = getCIRSourceLanguage();
+  if (sourceLanguage)
+    theModule->setAttr(
+        cir::CIRDialect::getSourceLanguageAttrName(),
+        cir::SourceLanguageAttr::get(&mlirContext, *sourceLanguage));
   theModule->setAttr(cir::CIRDialect::getTripleAttrName(),
                      builder.getStringAttr(getTriple().str()));
 
@@ -513,7 +515,7 @@ void CIRGenModule::setNonAliasAttributes(GlobalDecl gd, mlir::Operation *op) {
   assert(!cir::MissingFeatures::setTargetAttributes());
 }
 
-cir::SourceLanguage CIRGenModule::getCIRSourceLanguage() const {
+std::optional<cir::SourceLanguage> CIRGenModule::getCIRSourceLanguage() const {
   using ClangStd = clang::LangStandard;
   using CIRLang = cir::SourceLanguage;
   auto opts = getLangOpts();
@@ -528,6 +530,7 @@ cir::SourceLanguage CIRGenModule::getCIRSourceLanguage() const {
   // TODO(cir): support remaining source languages.
   assert(!cir::MissingFeatures::sourceLanguageCases());
   errorNYI("CIR does not yet support the given source language");
+  return std::nullopt;
 }
 
 static void setLinkageForGV(cir::GlobalOp &gv, const NamedDecl *nd) {
diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.h b/clang/lib/CIR/CodeGen/CIRGenModule.h
index d90baa55d0b5c..4f5c7f898af8c 100644
--- a/clang/lib/CIR/CodeGen/CIRGenModule.h
+++ b/clang/lib/CIR/CodeGen/CIRGenModule.h
@@ -480,7 +480,7 @@ class CIRGenModule : public CIRGenTypeCache {
   void setNonAliasAttributes(GlobalDecl gd, mlir::Operation *op);
 
   /// Map source language used to a CIR attribute.
-  cir::SourceLanguage getCIRSourceLanguage() const;
+  std::optional<cir::SourceLanguage> getCIRSourceLanguage() const;
 };
 } // namespace CIRGen