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Subject: Re: Another memory latency test (another comment) (more)

Author: Robert Hyatt

Date: 13:23:02 07/22/03

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By the way, if you are using gcc/icc, you can use the -S option to get
them to dump the .s file (the assembly code they produce).  You can look
at what the compiler is producing to see if you out-smarted yourself.

I've done that many times.  Ie a simple loop to burn cycles can get
thrown away as in:

for (i=0;i<100000000000;i++);

i=x;

the i=x shows the compiler that the original loop counter (i) is not
used, and the loop can be canned.  Without the i=x, the compiler has to
be sure that i is never referenced after the loop, which is easy with a
DAG.  But for the example above, anybody can produce the DAG to see that
the loop can be eliminated.



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