Re: why not inline all functions?

Mark Sanvitale wrote:
> Functions are great for making written code (C, C++, etc.) mode
> readable and structured, however, they do not seem to make much sense
> when you get down to the raw machine code which actually is executed
> by a processor.
>
> As far as my understanding of the matter goes, the most basic way to
> slow down a processor is to make it execute an instruction besides the
> one immediately following the current instruction, thus, why not make
> a compiler which turns every function into an inline function?
> "computer geek and movie freak"
> [ ... code bloat ... -John]


Yes, code bloat is one of the main gating factors for inlining.


Another is register pressure - function calls tend to use special
fast-path means for spilling/loading a large number of registers.
Standard allocators tend to spill one-by-one. Allocators also tend to
make fairly bad code when a large amount of spilling is required.
This "bad spilling" works on most RISCs because large register files
means spill code is rare --- as long as you throttle inlining.


Cliff


--
Cliff Click Compiler Designer and Researcher
cliffc at acm.org JavaSoft
(408) 863-3266 MS UCUP02-302
--

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