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Re: Effect of -fno-reorder-blocks?
- From: David Edelsohn <dje at watson dot ibm dot com>
- To: Hans-Peter Nilsson <hans-peter dot nilsson at axis dot com>
- Cc: dnovillo at redhat dot com, aj at suse dot de, gcc at gcc dot gnu dot org
- Date: Tue, 12 Nov 2002 12:32:51 -0500
- Subject: Re: Effect of -fno-reorder-blocks?
>>>>> Hans-Peter Nilsson writes:
Hans-Peter> I see unexpected results with a ss of gcc-3.2 (gcc-20020902). I
Hans-Peter> get better code with -fno-reorder-blocks *especially*
Hans-Peter> considering effects on the cache (a simple one: 8k unified
Hans-Peter> 1-way, 32-byte lines) for cris-axis-linux-gnu. I'll add more
Hans-Peter> substance to this claim once I've done more thorough testing,
Hans-Peter> with newer sources, though I believe no changes have been done
Hans-Peter> that would improve this. I wonder if there are similar effects
Hans-Peter> for other architectures, with more intricate branch timings and
Hans-Peter> cache semantics. I know about the the messages about SH and
Hans-Peter> -fno-reorder-blocks; that's the reason I tried it.
This affects PowerPC as well. See PR optmization/6990.
When I pointed this out to Honza last July , he mentioned that
this type of problem is addressed in the STC implementation on the CFG
branch. I am not sure about the current status of merging those
improvements.
David