X3J3/96-076

Date:    April 29, 1996
To:      X3J3
From:    Kurt W. Hirchert
Subject: JOR Item 110

  <FORTREQ>
  <NUMBER> 110
  <TITLE> In-line procedures
  <KEYWORDS> PROCEDURE, IN-LINE
  <STATUS> Registered
  <TARGET>
  <SUBGROUP>
  <VERSION> 1

  <REQUIREMENT>
  Provide a means for a programmer to specify that the desired implementation
  of that procedure is by in-line expansion of the code at the point of
  reference to the procedure rather than branch to and return from a single
  code image.

  <JUSTIFICATION>
  In almost any programming method involving significant data abstraction
  (including, but not limited to, object-oriented programming), there tend
  to be a number of procedures which bridge levels of abstraction, but which
  do little "real" work.  In-line expansion of such procedures significantly
  reduces their cost.  In addition, there tends to increased opportunities for
  optimization in the calling scoping unit.  [The value of in-line expansion
  of statement functions is well known and an example of what this requirement
  would provide in a somewhat broader context.]

  <SUGGESTED IMPLEMENTATION>
  Allow a keyword such as INLINE on the procedure header.

  Since we cannot reasonably directly require in-line expansion, the semantics
  of this keyword are to prohibit obstacles to in-line expansion:

  o  The INLINE keywords would be permitted on module procedures and internal
     procedures, but not external procedures or interface bodies.

  o  A procedure could not be both INLINE and RECURSIVE.

  o  An INLINE procedure could not be associated with a dummy procedure (nor
     with a pointer to a procedure, if we add those).

  We would have to leave it to market pressure to actually ensure that INLINE
  procedures are expanded in-line.

  <ESTIMATED IMPACT>
  The impact on the document should be well localized.

  Impact on existing processors will vary:  A processor wishing to meet the
  literal requirements (without actually doing in-line expansion) could do
  so with a small amount of syntax checking.

  Typically, existing processors already do at least some in-line expansion
  (for statement functions) and some do in-line expansion of arbitrary
  procedures, but it seems likely that it will vary from processor whether
  the existing in-line expansion infrastructure is sufficient for doing
  the kind of expansion expected in this requirement.

  <SUBMITTED BY> Kurt W. Hirchert, hirchert@ncsa.uiuc.edu

  <HISTORY>
  <EVENT> 29 April 96: submitted
  </HISTORY>

  </FORTREQ>

--
Kurt W. Hirchert     hirchert@ncsa.uiuc.edu
National Center for Supercomputing Applications