Problem with testing libstdc++ parallel headers?

[sje@cup.hp.com]

I was looking into why parallel tests like 
25_algorithms/headers/algorithm/algorithm_parallel_mode.cc
were failing on IA64 HP-UX and I found lines like:

 #pragma message: slow fetch_and_add_64
 #pragma message: slow compare_and_swap_64

OK, I looked at compatibility.h and basically understood why I get
these messages but then I went to IA64 Linux where I didn't see
these messages in order to see how the test passes there and I see:

UNSUPPORTED: 25_algorithms/headers/algorithm/algorithm_parallel_mode.cc

along with lines like:

parallel_mode31631.cc:1:17: error: omp.h: No such file or directory

This seems odd ot me since I am building libgomp with my compiler.

And when I saw the same messages in my x86_64 build, then I got
really suspicious.

Is there a known problem on Linux where we aren't testing the parallel
algorithms that we should be testing because check_v3_target_parallel_mode
is saying that we don't support a parallel mode?

Steve Ellcey
sje@cup.hp.com