Mail Archives: djgpp/1998/01/27/19:01:11
Richard Chappell wrote:
>
> What does optimization do?? Does it make your exe file smaller, or
> faster, or what??
Yes, yes, and yes. :-) Optimization allows the compiler to figure out
ways to make code run faster. This almost always results in size
savings as well. The exact details of what the compiler does to
optimize your code are complex; I suggest you look in the gcc
documentation to find out all the potential benefits.
Some basic optimizations include:
- Putting frequently used variables into registers to reduce the time
required for memory access.
- Using "shortcuts" to make arithmetic calculations run faster (shifts
instead of multiplies with powers of 2, for instance).
- Changing around the order of conditional and looping statements to
make more frequently used code come first.
- Implementing branching structures like switch() statements as lookup
tables instead of a series of tests.
- Eliminating code that has no apparent purpose.
- Inlining functions.
There's lots more.
--
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| John M. Aldrich | "To be 'matter of fact' about the |
| aka Fighteer I | world is to blunder into fantasy-- |
| mailto:fighteer AT cs DOT com | and dull fantasy at that, as the real|
| http://www.cs.com/fighteer | world is strange and wonderful." -LL |
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