[clang] Fix CodeGenAction for LLVM IR MemBuffers

[RSenApps]

Summary

Replaces use of getCurrentFile with getCurrentFileOrBufferName
in CodeGenAction. This avoids an assertion error or an incorrect
name chosen for the output file when assertions are disabled.
This error previously occurred when the FrontendInputFile was a
MemoryBuffer instead of a file.

[jlebar]

Congrats on your first patch!

Can Daniele or Shangwu land this for you, or do you need me to?

[dcastagna]

I'll land it.

clang/lib/CodeGen/CodeGenAction.cpp

void CodeGenAction::ExecuteAction() {
   }
 
   // If this is an IR file, we have to treat it specially.
   BackendAction BA = static_cast<BackendAction>(Act);
   CompilerInstance &CI = getCompilerInstance();
   auto &CodeGenOpts = CI.getCodeGenOpts();
   auto &Diagnostics = CI.getDiagnostics();
   std::unique_ptr<raw_pwrite_stream> OS =
-      GetOutputStream(CI, getCurrentFile(), BA);
+      GetOutputStream(CI, getCurrentFileOrBufferName(), BA);
   if (BA != Backend_EmitNothing && !OS)
     return;
 
   SourceManager &SM = CI.getSourceManager();
   FileID FID = SM.getMainFileID();
   Optional<MemoryBufferRef> MainFile = SM.getBufferOrNone(FID);
   if (!MainFile)
     return;

clang/unittests/Frontend/CodeGenActionTest.cpp

TEST(CodeGenTest, TestNullCodeGen) {
   Compiler.createDiagnostics();
   EXPECT_TRUE(Compiler.hasDiagnostics());
 
   std::unique_ptr<FrontendAction> Act(new NullCodeGenAction);
   bool Success = Compiler.ExecuteAction(*Act);
   EXPECT_TRUE(Success);
 }
 
+TEST(CodeGenTest, CodeGenFromIRMemBuffer) {
+  auto Invocation = std::make_shared<CompilerInvocation>();
+  std::unique_ptr<MemoryBuffer> MemBuffer =
+      MemoryBuffer::getMemBuffer("", "test.ll");
+  Invocation->getFrontendOpts().Inputs.push_back(
+      FrontendInputFile(*MemBuffer, Language::LLVM_IR));
+  Invocation->getFrontendOpts().ProgramAction = frontend::EmitLLVMOnly;
+  Invocation->getTargetOpts().Triple = "i386-unknown-linux-gnu";
+  CompilerInstance Compiler;
+  Compiler.setInvocation(std::move(Invocation));
+  Compiler.createDiagnostics();
+  EXPECT_TRUE(Compiler.hasDiagnostics());
+
+  EmitLLVMOnlyAction Action;
+  bool Success = Compiler.ExecuteAction(Action);
+  EXPECT_TRUE(Success);
+}
 }