[fpc-devel] Array indexing vs. pointers

[Jim Leonard]

On 11/7/2013 6:21 AM, Sven Barth wrote:
> The resulting instructions depend highly on the architecture. E.g. on
> x86 and m68k for the first case a MOV/MOVE instruction with a multiplier
> will be used while on other platforms this might involve an explicit
> multiplication. Also it will depend on the optimization level you use
> (e.g. on x86 the generated code for the first case is very different
> between -O2 and -O3). In the end you'd need to calculate the instruction
> timings to know whether one of the two is really faster than the other
> (and then you can compare that later on with your own implementation to
> check whether your code or the compiler's is faster ^^)

I'm on x86.  I was hoping for a little more than "profile it to find 
out" (for example, if pointers are optimized to be in indexing registers 
then it should be obvious that is fastest), but if I have to do that, 
then I guess that's what I'll have to do.

I suppose I can just write a short program that indexes data many 
different ways and then examine the asm output.
-- 
Jim Leonard (trixter at oldskool.org)
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