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Re: [Bug tree-optimization/21829] [4.1/4.2 Regression] missed jump threading after unroller
- From: "Richard Guenther" <richard dot guenther at gmail dot com>
- To: law at redhat dot com
- Cc: gcc-bugzilla at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Wed, 22 Mar 2006 12:14:27 +0100
- Subject: Re: [Bug tree-optimization/21829] [4.1/4.2 Regression] missed jump threading after unroller
- References: <bug-21829-6528@http.gcc.gnu.org/bugzilla/> <20060211005940.30518.qmail@sourceware.org> <1142917666.23430.71.camel@to-dhcp19.toronto.redhat.com>
On 3/21/06, Jeffrey A Law <law@redhat.com> wrote:
> It turns out this specialized PHI optimization pass is as effective
> as running copy-prop and CCP on PHI nodes after DOM. Better yet, it
> is a teeny tiny slowdown compared to just running the stripped down
> copyprop. ie, for an almost unmeasurable slowdown we can do both
> constant and copy propagation instead of just copy propagation.
This patch caused a compile-time regression from 139s to 143s, resp.
192s to 197s (leafify) accounted by increases of operand scan / SSA incremental
and tree CCP times for compiling tramp3d. Also memory usage during compiling
went up from 655494 kB to 660626kB (this may be due to the VRP patch, though).
Runtime of tramp3d did not improve but regress slightly (but that
might be in the
noise - we'll see).
For this simple cleanup pass can you try updating SSA form manually please?
Thanks,
Richard.