finding out what an optimizer did?

[Steven T. Hatton]

Can someone suggest guideline to follow in determining what an optimizer has
eliminated from the prescribed execution sequence? Any particular tools
people use for this? I'm working on a Linux platform. I can look at the
disassembler output, and trace the instruction pointer, but when the code
is compiled with optimization I can't see how the current instruction
relates to the original source code.

--
NOUN:1. Money or property bequeathed to another by will. 2. Something handed
down from an ancestor or a predecessor or from the past: a legacy of
religious freedom. ETYMOLOGY: MidE legacie, office of a deputy, from OF,
from ML legatia, from L legare, to depute, bequeath. www.bartleby.com/61/

[Thomas Krog]

You can add function calls for which the implementation is located in
another compilation unit - in this way you shold be able to find the
function call in the assembly. You can also pass arguments to the
function to force these arguments to be calculated before the function
call.

[Kevin Handy]

Steven T. Hatton wrote:

Can someone suggest guideline to follow in determining what an optimizer has
eliminated from the prescribed execution sequence? Any particular tools
people use for this? I'm working on a Linux platform. I can look at the
disassembler output, and trace the instruction pointer, but when the code
is compiled with optimization I can't see how the current instruction
relates to the original source code.

Start the compiler in a gdb (or similiar) debugger,
then single step through the compiler. You sould be able
to see exactly what the optimizater does to your code.

Other than that, you are only going to be guessing.

The optimization is very dependent on the compiler, which
version it is, what options were selected, etc.
It's equivelent to running a steak through a leaky meat
grinder. Lots of stuff comes out, and some of it lands
on the floor, but if you try to determine where each bit
of meat originally came from, it's not going to be easy.

If you want to use the debugger, you should turn off
optimizations. Otherwise, you'll never know what code is
actually being executed, and any minor edit could
completely change the execution sequence.

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----