[BuildingAJIT] Update the Ch1 KaleidoscopeJIT class to expose errors to clients.

Returning the error to clients provides an opportunity to introduce readers to
the Expected and Error APIs and makes the tutorial more useful as a starting
point for a real JIT class, while only slightly complicating the code.

llvm-svn: 344720

2 files changed, 38 insertions, 36 deletions

diff --git a/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/KaleidoscopeJIT.h b/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/KaleidoscopeJIT.h
index d9e320f5478..1df5aff0869 100644
--- a/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/KaleidoscopeJIT.h
+++ b/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/KaleidoscopeJIT.h
@@ -32,37 +32,45 @@ namespace orc {
 
 class KaleidoscopeJIT {
 private:
-
   ExecutionSession ES;
-  RTDyldObjectLinkingLayer ObjectLayer{ES, getMemoryMgr};
-  IRCompileLayer CompileLayer{ES, ObjectLayer,
-                              ConcurrentIRCompiler(getJTMB())};
-  DataLayout DL{cantFail(getJTMB().getDefaultDataLayoutForTarget())};
-  MangleAndInterner Mangle{ES, DL};
-  ThreadSafeContext Ctx{llvm::make_unique<LLVMContext>()};
-
-  static JITTargetMachineBuilder getJTMB() {
-    return cantFail(JITTargetMachineBuilder::detectHost());
-  }
+  RTDyldObjectLinkingLayer ObjectLayer;
+  IRCompileLayer CompileLayer;
 
-  static std::unique_ptr<SectionMemoryManager> getMemoryMgr() {
-    return llvm::make_unique<SectionMemoryManager>();
-  }
+  DataLayout DL;
+  MangleAndInterner Mangle;
+  ThreadSafeContext Ctx;
 
 public:
-
-  KaleidoscopeJIT() {
+  KaleidoscopeJIT(JITTargetMachineBuilder JTMB, DataLayout DL)
+      : ObjectLayer(ES,
+                    []() { return llvm::make_unique<SectionMemoryManager>(); }),
+        CompileLayer(ES, ObjectLayer, ConcurrentIRCompiler(std::move(JTMB))),
+        DL(std::move(DL)), Mangle(ES, this->DL),
+        Ctx(llvm::make_unique<LLVMContext>()) {
     ES.getMainJITDylib().setGenerator(
-      cantFail(DynamicLibrarySearchGenerator::GetForCurrentProcess(DL)));
+        cantFail(DynamicLibrarySearchGenerator::GetForCurrentProcess(DL)));
+  }
+
+  static Expected<std::unique_ptr<KaleidoscopeJIT>> Create() {
+    auto JTMB = JITTargetMachineBuilder::detectHost();
+
+    if (!JTMB)
+      return JTMB.takeError();
+
+    auto DL = JTMB->getDefaultDataLayoutForTarget();
+    if (!DL)
+      return DL.takeError();
+
+    return llvm::make_unique<KaleidoscopeJIT>(std::move(*JTMB), std::move(*DL));
   }
 
   const DataLayout &getDataLayout() const { return DL; }
 
   LLVMContext &getContext() { return *Ctx.getContext(); }
 
-  void addModule(std::unique_ptr<Module> M) {
-    cantFail(CompileLayer.add(ES.getMainJITDylib(),
-                              ThreadSafeModule(std::move(M), Ctx)));
+  Error addModule(std::unique_ptr<Module> M) {
+    return CompileLayer.add(ES.getMainJITDylib(),
+                            ThreadSafeModule(std::move(M), Ctx));
   }
 
   Expected<JITEvaluatedSymbol> lookup(StringRef Name) {
diff --git a/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/toy.cpp b/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/toy.cpp
index 1d0730f99ef..5a66b367c27 100644
--- a/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/toy.cpp
+++ b/llvm/examples/Kaleidoscope/BuildingAJIT/Chapter1/toy.cpp
@@ -703,6 +703,7 @@ static std::unique_ptr<IRBuilder<>> Builder;
 static std::unique_ptr<Module> TheModule;
 static std::map<std::string, AllocaInst *> NamedValues;
 static std::map<std::string, std::unique_ptr<PrototypeAST>> FunctionProtos;
+static ExitOnError ExitOnErr;
 
 Value *LogErrorV(const char *Str) {
   LogError(Str);
@@ -1116,7 +1117,7 @@ static void HandleDefinition() {
       fprintf(stderr, "Read function definition:");
       FnIR->print(errs());
       fprintf(stderr, "\n");
-      TheJIT->addModule(std::move(TheModule));
+      ExitOnErr(TheJIT->addModule(std::move(TheModule)));
       InitializeModule();
     }
   } else {
@@ -1151,23 +1152,16 @@ static void HandleTopLevelExpression() {
     if (FnAST->codegen()) {
       // JIT the module containing the anonymous expression, keeping a handle so
       // we can free it later.
-      TheJIT->addModule(std::move(TheModule));
+      ExitOnErr(TheJIT->addModule(std::move(TheModule)));
       InitializeModule();
 
       // Get the anonymous expression's JITSymbol.
-      auto Sym =  TheJIT->lookup(("__anon_expr" + Twine(ExprCount)).str());
-
-      if (Sym) {
-        // If the lookup succeeded, cast the symbol's address to a function
-        // pointer then call it.
-        auto *FP = (double (*)())(intptr_t)Sym->getAddress();
-        assert(FP && "Failed to codegen function");
-        fprintf(stderr, "Evaluated to %f\n", FP());
-      } else {
-        // Otherwise log the reason the symbol lookup failed.
-        logAllUnhandledErrors(Sym.takeError(), errs(),
-                              "Could not evaluate: ");
-      }
+      auto Sym =
+        ExitOnErr(TheJIT->lookup(("__anon_expr" + Twine(ExprCount)).str()));
+
+      auto *FP = (double (*)())(intptr_t)Sym.getAddress();
+      assert(FP && "Failed to codegen function");
+      fprintf(stderr, "Evaluated to %f\n", FP());
     }
   } else {
     // Skip token for error recovery.
@@ -1235,7 +1229,7 @@ int main() {
   fprintf(stderr, "ready> ");
   getNextToken();
 
-  TheJIT = llvm::make_unique<KaleidoscopeJIT>();
+  TheJIT = ExitOnErr(KaleidoscopeJIT::Create());
   TheContext = &TheJIT->getContext();
 
   InitializeModule();