[www] Document C++ -O0 improvements
Paolo Bonzini
bonzini@gnu.org
Thu Oct 28 09:44:00 GMT 2004
> + <li>When compiling without optimizations (-O0), the C++ frontend is
> + <strong>much</strong> faster than in any previous versions of GCC.
> + Independent testers have measured speed-ups up to 25% in real-world
> + production code, compared to the 3.4 family (which was already the
> + fastest version to date). Upgrading from older versions might show
> + even bigger improvements.</li>
What about C? Some patches should have also given some improvements,
though not as extreme (C++ had lexing upfront, precedence parsing,
etc.). For example
http://gcc.gnu.org/ml/gcc-patches/2004-10/msg02060.html (c_lex speedup)
http://gcc.gnu.org/ml/gcc-patches/2004-10/msg01879.html (edge vector)
http://gcc.gnu.org/ml/gcc-patches/2004-08/msg01318.html (share int_cst)
http://gcc.gnu.org/ml/gcc-patches/2004-06/msg01417.html (cfg expansion)
would apply to C as well. The last one has mostly fixed the -O0
regressions introduced by tree-ssa, but was an improvement anyway.
What about
<li>When compiling without optimizations (-O0), GCC will be faster than
any previous version. This is especially true for the C++ front-end,
for which independent testers have measured speed-ups up to 25% in
real-world production code, compared to the 3.4 family (which was
<strong>already</strong> the fastest version to date). Upgrading from
older versions might show even bigger improvements.</li>
Paolo
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