Re: GCC 3.3 release criteria

[Bernd Schmidt <bernds at redhat dot com>]

On Tue, 25 Feb 2003, Richard Earnshaw wrote:

> The cases in C where I've seen people get most upset about the compiler 
> not using inline are when the program has subtly different semantics once 
> inlining has occurred (for example, taking the address of a label and then 
> using that as a key in a debug message).  But these are precisely the 
> types of cases where we probably don't want inlining: relying on such 
> optimization to get correct behaviour is a dangerous mistake.

I was rather upset when I discovered the inline keyword was no longer
honoured by gcc.  One of my applications uses inlining to reduce code
duplication without hurting performance.  I have a few time-critical
functions of the form

inline void f (int arg1, int arg2, int arg3)
{
   ... several loops deep..
   {
       if (arg1 == 1)
	  foo;
       else
	  bar;
   }
}

I know the range of the values the arguments can have, and I use inlining
to move the tests out of the loops without having to duplicate all the
loop bodies by hand.

I have 
  void f_2_3_1 () { f (2, 3, 1); }
etc. (these will expand into optimized versions of f) as well as a frontend
function that takes arg1, arg2 and arg3 and decides which of the f_x_y_z
to call.

The effect is maybe slightly similar to C++ templates.  Needless to say,
it completely fell apart with gcc-3.0 which decided it was smarter than
the programmer.

I would like something like -fobey-inline to be the default.


Bernd