llvm-reduce: Report file opening errors

[arsenm]

Summary

This was also trying to write the bitcode to the failed file
on failure, which asserts. Also, consistently use
ToolOutputFile, instead of one path manually removing
the temp file.

[aeubanks]

llvm/tools/llvm-reduce/deltas/Delta.cpp

81–82

I think the intention of the original code was also to check if the writing caused any problems. So we should check before and after? And ditto below in the textual IR. Probably we should factor out the check into a helper function/lambda

[arsenm]

Consistently use ToolOutputFile and check error after close

[aeubanks]

oh I guess if there's an error opening the file initially, it'll stay as that error even attempting to write to it?

[arsenm]

In D136614#3897470, @aeubanks wrote:

oh I guess if there's an error opening the file initially, it'll stay as that error even attempting to write to it?

No, it's an assert to write to the failed open file. This ends up checking after open and after close. The problem was the text and bitcode paths were duplicating the opening, and the text path didn't check

[arsenm]

4cf5e22d20dfb725e92b57c7ac4bba65d7cd62be

llvm/tools/llvm-reduce/deltas/Delta.cpp

bool isReduced(ReducerWorkItem &M, TestRunner &Test) {
   int FD;
   std::error_code EC = sys::fs::createTemporaryFile(
       "llvm-reduce", M.isMIR() ? "mir" : (TmpFilesAsBitcode ? "bc" : "ll"), FD,
       CurrentFilepath);
   if (EC) {
     errs() << "Error making unique filename: " << EC.message() << "!\n";
     exit(1);
   }
 
-  if (TmpFilesAsBitcode) {
-    llvm::raw_fd_ostream OutStream(FD, true);
-    writeBitcode(M, OutStream);
-    OutStream.close();
-    if (OutStream.has_error()) {
-      errs() << "Error emitting bitcode to file '" << CurrentFilepath << "'!\n";
-      sys::fs::remove(CurrentFilepath);
-      exit(1);
-    }
-    bool Res = Test.run(CurrentFilepath);
-    sys::fs::remove(CurrentFilepath);
-    return Res;
-  }
   ToolOutputFile Out(CurrentFilepath, FD);
+
+  if (TmpFilesAsBitcode)
+    writeBitcode(M, Out.os());
+  else
     M.print(Out.os(), /*AnnotationWriter=*/nullptr);
+
   Out.os().close();
   if (Out.os().has_error()) {
-    errs() << "Error emitting bitcode to file '" << CurrentFilepath << "'!\n";
+    errs() << "Error emitting bitcode to file '" << CurrentFilepath
+           << "': " << Out.os().error().message();
     exit(1);
   }
 
   // Current Chunks aren't interesting
   return Test.run(CurrentFilepath);
 }
 
 /// Splits Chunks in half and prints them.