Fix -fwhole-program on LTO -- Another SPEC2000 benchmakring round

[Diego Novillo]

On Thu, Oct 8, 2009 at 11:32, Steven Bosscher <stevenb.gcc@gmail.com> wrote:

> Is this kind of slow-down expected (i.e. similar to LTO cost of other
> compilers)?

Yes, we compile everything twice since .o files have both final object
code and gimple bytecode.  Add to that the penalty of doing IPA over
larger callgraphs.  We have some large polynomial algorithms there.
On a very large internal application we spend 30 CPU minutes making
inlining decisions.

There is also the penalty of streaming bytecode.  -ftime-report breaks
those down.  I don't recall exact figures, but streaming was not a
significant factor.


Diego.