Path: utzoo!attcan!uunet!dino!sharkey!msuinfo!news
From: riordanmr@clvax1.cl.msu.edu (Mark Riordan)
Newsgroups: comp.arch
Subject: Inlining subroutines at link time
Message-ID: <1990Jul3.194348.21178@msuinfo.cl.msu.edu>
Date: 3 Jul 90 19:43:48 GMT
Sender: news@msuinfo.cl.msu.edu
Organization: Michigan State University
Lines: 34

I just came across a CDC NOS/VE manual describing a facility to 
inline FORTRAN routines after compilation (essentially during linking).
I no longer have access to a NOS/VE system, so I don't know how well
this works, but it seems like a fairly unique feature to me.  Have
you folks ever heard of a similar system?

I quote from the April 88 revision of the Control Data NOS/VE Object
Code Management guide:

"The AFTERBURN_OBJECT_TEXT command improves the execution time of
FORTRAN Version 1 and Version 2 programs by inlining subprograms.
Inlining a subprogram places the statements of the subprogram in the
code where the routine is called.  Inlining subprograms is an optimization
process that trades space for execution time.  Modules with inlined
subprograms are larger, yet they execute faster because they avoid 
call and return instructions, which increase execution time.

The afterburner works on bound modules and can be thought of as
an extension to the binding process.  A bound module is the usual input
to the afterburner, but if an object file is used, all modules in the file
are bound into one module named NEW.  The output from the afterburner
is a new module, with subprograms, or modules, expanded inline.

The afterburner requires no source code changes.  Existing programs
or subroutines can have subprograms expanded inline without changing
the program or subroutine.  For example, a FORTRAN program can
expand a math library routine inline without recompiling.  Since
afterburning occurs as a separate step after compilation, compilation
time is not affected.

The afterburned performs a cost/benefit analysis to determine if a
specific routine should be brought inline.  If a subroutine is called in
two places, it might be profitable to inline the subroutine in one
instance and not the other."