unroll-loops - Is it always safe?

Gary Kline kline at tao.thought.org
Thu Apr 5 15:41:52 UTC 2007

On Thu, Apr 05, 2007 at 09:54:08AM -0300, scuba at centroin.com.br wrote:
> Hi All,
> 	Is it always safe to use "-funroll-loops" as a flag to 
> /etc/make.conf ? Does it realy improve the compiled programs?
> 	When should I avoid to use it?

	If you are using gcc42 -funroll-loops can be a win. gcc3.x
	is less savvy about knowing the limits of complexity to unroll
	which loops.  I'm doing some tests with gcc34 (default) and
	gcc42. The latter can yield significant improvements  iff
	you know what you're doing.  It's no magic bullet.


> - Marcelo
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  Gary Kline  kline at thought.org   www.thought.org  Public Service Unix

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