[Bug bootstrap/54419] [4.8 Regression] Compiling libstdc++-v3/src/c++11/random.cc fails on platforms not knowing rdrand

[drepper.fsp at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54419

--- Comment #9 from Ulrich Drepper <drepper.fsp at gmail dot com> 2012-08-31 17:46:41 UTC ---
(In reply to comment #8)
> Is it clear which are the specific requirements for the various x86* targets?
> I'm wondering if after all it's just matter of updating:
> http://gcc.gnu.org/install/specific.html

Indeed.  You cannot use old binutils if any of the code generated by the
compiler requires something newer.  If these dependencies are not wanted then
make the compiler to emit .byte sequences when the new builtins are used.


> Since rdrand is only supported on Ivy Bridge processors, shouldn't
> src/c++11/random.cc have a fall through using rdtsc in case the processor
> doesn't support rdrand?

Read the code.  There is of course a fall-through for older processors.  This
is about the code generated by the compiler, not what is used at runtime.