Building the ACATS tests at -O3 causes one additional failure: cxg2021.

This went away when the gcc inliner was disabled.  Most likely
the underlying problem has just been covered up, but I don't
care enough to investigate further.  Note that the original
failure only occurred when using the x86 floating point stack,
and not when using sse registers.

This recently started failing again (at -O2).

Remarks: this seems to be due to extra precision in x86-32 floating
point registers versus the precision (64 bits) when stored to a stack
slot.  The test is testing 64 bit precision, and as far as I can see
it shouldn't matter whether you use stack stores or registers, since
both give values inside the Ada "model interval" (Ada uses an interval
arithmetic model for floating point).  I wasn't able to find anything
obviously wrong with the LLVM generated code.  Currently I suspect that
the test is wrong, but didn't finish analyzing it yet.

still a problem?

Yes, still a problem.  In fact it now fails at -O2!  It is not clear if this
is a bug in LLVM or in the test.  In order to resolve this I wrote my own
simulator of Ada floating point interval arithmetic, but having done so never
found the time to apply it to the analysis of this test, d'oh!