[lto] preliminary SPECint benchmark numbers

[Chris Lattner]

On Dec 25, 2007, at 5:02 PM, Vladimir N. Makarov wrote:

> Here is mine benchmarking of the current LTO branch on 2.66Ghz Core2
> under RHEL 5 in 64- and 32-bits mode.  The vortex violates type
> aliasing rules, therefore it should be compiled with
> -fno-strict-aliasing.  Perlbmk crashed in tree.c::build2_stat in
> 32-bits mode when LTO used.  LTO currently generates wrong code for
> 176.gcc.  I've also checked Specfp2000 benchmarks written in C.
>
> In brief,
>
> o the code size (text segment) with LTO is much smaller (2.7% and
>   2.4% for SpecInt and 0.16% and 0.6% for SpecFp correspondingly in  
> 64-
>   and 32-bit mode).  That is very promising.
> o the compilation is 2 times slower with LTO.
> o The generated code is slower 3.6% and 2.2% for SPECint2000 and
>   SpecFp2000 in 64-bit mode.  It is also 6.7% slower for SpecInt2000  
> in
>   32-bit mode.  But SpecFp2000 in 32-bit mode code generated with LTO
>   is 20% faster!  It is because art is almost 2.5 times faster with
>   LTO.

Wow, nice numbers! Is it possible to compare this to -combine, or does  
-combine work anymore?  In theory, lto and IMA should yield the same  
codegen, lto should just be usable with normal makefiles.

-Chris