[clang] [clang-repl] Factor out CreateJITBuilder() and allow specialization in derived classes (PR #84461)

[Stefan Gränitz via cfe-commits]

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@@ -373,21 +373,32 @@ Interpreter::Parse(llvm::StringRef Code) {
 static llvm::Expected<llvm::orc::JITTargetMachineBuilder>
 createJITTargetMachineBuilder(const std::string &TT) {
   if (TT == llvm::sys::getProcessTriple())
+    // This fails immediately if the target backend is not registered
     return llvm::orc::JITTargetMachineBuilder::detectHost();
-  // FIXME: This can fail as well if the target is not registered! We just don't
-  // catch it yet.
+
+  // If the target backend is not registered, LLJITBuilder::create() will fail
   return llvm::orc::JITTargetMachineBuilder(llvm::Triple(TT));
 }
 
+llvm::Expected<std::unique_ptr<llvm::orc::LLJITBuilder>>
+Interpreter::CreateJITBuilder(CompilerInstance &CI) {
+  auto JTMB = createJITTargetMachineBuilder(CI.getTargetOpts().Triple);
+  if (!JTMB)
+    return JTMB.takeError();
+  return IncrementalExecutor::createDefaultJITBuilder(std::move(*JTMB));
+}
+
 llvm::Error Interpreter::CreateExecutor() {
-  const clang::TargetInfo &TI =
-      getCompilerInstance()->getASTContext().getTargetInfo();
   if (IncrExecutor)
     return llvm::make_error<llvm::StringError>("Operation failed. "
                                                "Execution engine exists",
                                                std::error_code());
+  llvm::Expected<std::unique_ptr<llvm::orc::LLJITBuilder>> JB =
+      CreateJITBuilder(*getCompilerInstance());
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weliveindetail wrote:

We keep creating a new LLJITBuilder for each new IncrementalExecutor. This is questionable, but I didn't want to clutter the patch unnecessarily. I am happy to change that in a follow-up PR.

https://github.com/llvm/llvm-project/pull/84461