Re: std::pow implementation

[Richard Earnshaw <rearnsha at arm dot com>]

> Richard Earnshaw <rearnsha@arm.com> writes:
> 
> [...]
> 
> | Now, assume that the amount of code in the a!=1 case is reduced.  At what 
> | point does it become beneficial to always inline?  Can the programmer 
> | tell?
> 
> He can profile.

Profiling doesn't help if the answer comes back as "sometimes" (function 
foo's use of bar is best inlined, function wibble's use of bar is best not 
inlined).

> 
> |  Should he write the code in a separate function, or should he leave 
> | it to the compiler to decide?  What happens if the code is ported to 
> | another machine with twice as many registers?
> 
> Let's not have the compiler speculate about the future plateform the
> programmer will run his program on -- it has no clue.

And nor, necessarily, can the programmer who writes a class definition.  
Don't forget that it may end up being used by other programmers who have 
no power to change the class interface.

> 
> | With Gaby's suggested interpretation, the compiler has *no* choice; it 
> | must obey the inlining constraint because the programmer always knows 
> | better...  Even when prepared to admit that he doesn't.
> 
> That assertion is wrong.

Which bit of it?  It's what I understand you to be suggesting.

R.