llvm-reduce: Color output of child processes

[arsenm]

Summary

When reducing llvm-reduce with llvm-reduce, it can be confusing
to figure out what lines are printed by the child or parent. Not
sure this is the most reliable way to set and restore this.

[aeubanks]

does this handle stderr output?

[arsenm]

In D135632#3848368, @aeubanks wrote:

does this handle stderr output?

Yes. They seem to not be independently settable. I originally set both with different colors but the second one always applied to both

[arsenm]

86e9181ded7c5b6aa67a3a84089fce850c84f27a

[arsenm]

I am noticing some instances not getting the output colored when using parallel reduction

[arsenm]

In D135632#3856600, @arsenm wrote:

I am noticing some instances not getting the output colored when using parallel reduction

Also getting incorrectly colored parent output

[aeubanks]

given that the streams are global, I guess we shouldn't do this with parallel execution, unless we somehow serialize that output

[aeubanks]

we should probably revert this or somehow fix forward

[aeubanks]

I've reverted in 29cf7dffb81b0522231b1c154de108e059d8a4f0 because I think this is breaking an msan bot, see that commit description. (probably not doing this with parallel reduction is good enough)

[arsenm]

In D135632#3863359, @aeubanks wrote:

I've reverted in 29cf7dffb81b0522231b1c154de108e059d8a4f0 because I think this is breaking an msan bot, see that commit description. (probably not doing this with parallel reduction is good enough)

The parallel debug log is also pretty annoying. I was thinking of capturing the output and ensuring a printed order

llvm/tools/llvm-reduce/TestRunner.cpp

int TestRunner::run(StringRef Filename) {
 
   std::string ErrMsg;
   SmallVector<Optional<StringRef>, 3> Redirects;
   Optional<StringRef> Empty = StringRef();
   if (!Verbose) {
     for (int i = 0; i < 3; ++i)
       Redirects.push_back(Empty);
   }
+
+  outs().changeColor(raw_ostream::YELLOW);
+
   int Result =
       sys::ExecuteAndWait(TestName, ProgramArgs, /*Env=*/None, Redirects,
                           /*SecondsToWait=*/0, /*MemoryLimit=*/0, &ErrMsg);
+  outs().resetColor();
 
   if (Result < 0) {
     Error E = make_error<StringError>("Error running interesting-ness test: " +
                                           ErrMsg,
                                       inconvertibleErrorCode());
     errs() << toString(std::move(E));
     exit(1);
   }
 
   return !Result;
 }
 
 void TestRunner::setProgram(std::unique_ptr<ReducerWorkItem> P) {
   assert(P && "Setting null program?");
   Program = std::move(P);
 }