RFR(S): 8201368: IfNode::fold_compares() may lead to incorrect execution

[Roland Westrelin]

Hi Nils,

Thanks for reviewing this.

> Add "-Xmixed" to the test commandline to disable -Xcomp for this test. 
> -XX:-BackgroundCompilation is costly in combination with -Xcomp.

-Xcomp causes BackgroundCompilation to be set to false AFAICT:

void Arguments::set_mode_flags(Mode mode) {
...
  switch (mode) {
  default:
    ShouldNotReachHere();
    break;
  case _int:
    UseCompiler              = false;
    UseLoopCounter           = false;
    AlwaysCompileLoopMethods = false;
    UseOnStackReplacement    = false;
    break;
  case _mixed:
    // same as default
    break;
  case _comp:
    UseInterpreter           = false;
    BackgroundCompilation    = false;

Roland.