[doc] deprecate the old pipeline description

[doc] deprecate the old pipeline description

[Steven Bosscher]

Nobody has objected, so I guess we can go ahead and deprecate the
old pipeline description.  Attached is a patch for the internals
manual.  Should it be mentioned elsewhere too?

Gr.
Steven


	* md.texi (Processor pipeline description): Mention that the old
	pipeline description is deprecated.

Index: doc/md.texi
===================================================================
RCS file: /cvs/gcc/gcc/gcc/doc/md.texi,v
retrieving revision 1.104
diff -c -3 -p -r1.104 md.texi
*** doc/md.texi	8 Jul 2004 03:40:34 -0000	1.104
--- doc/md.texi	9 Jul 2004 15:48:29 -0000
*************** instruction scheduler has to have an ade
*** 5536,5545 ****
  processor parallelism (or @dfn{pipeline description}).  Currently GCC
  provides two alternative ways to describe processor parallelism,
  both described below.  The first method is outlined in the next section;
! it was once the only method provided by GCC, and thus is used in a number
! of exiting ports.  The second, and preferred method, specifies functional
! unit reservations for groups of instructions with the aid of @dfn{regular
! expressions}.  This is called the @dfn{automaton based description}.
  
  The GCC instruction scheduler uses a @dfn{pipeline hazard recognizer} to
  figure out the possibility of the instruction issue by the processor
--- 5536,5550 ----
  processor parallelism (or @dfn{pipeline description}).  Currently GCC
  provides two alternative ways to describe processor parallelism,
  both described below.  The first method is outlined in the next section;
! it specifies functional unit reservations for groups of instructions
! with the aid of @dfn{regular expressions}.  This is called the
! @dfn{automaton based description}.  The second method is called the
! @dfn{old pipeline description}.  This method specifies usage of
! function units for classes of insns.  This description is not as
! powerful or accurate as the automaton based description, because it
! is impossible to model instructions that use more than one function
! unit.  The second method is deprecated; new ports should use the
! automaton based description.
  
  The GCC instruction scheduler uses a @dfn{pipeline hazard recognizer} to
  figure out the possibility of the instruction issue by the processor
*************** generated from the old description.  Fur
*** 5552,5571 ****
  on processor complexity.  The instruction issue is possible if there is
  a transition from one automaton state to another one.
  
- You can use either model to describe processor pipeline
- characteristics or even mix them.  You could use the old description
- for some processor submodels and the @acronym{DFA}-based one for other
- processor submodels.
- 
- In general, using the automaton based description is preferred.  Its
- model is richer and makes it possible to more accurately describe
- pipeline characteristics of processors, which results in improved
- code quality (although sometimes only marginally).  It will also be
- used as an infrastructure to implement sophisticated and practical
- instruction scheduling which will try many instruction sequences to
- choose the best one.
- 
- 
  @menu
  * Old pipeline description:: Specifying information for insn scheduling.
  * Automaton pipeline description:: Describing insn pipeline characteristics.
--- 5557,5562 ----
*************** choose the best one.
*** 5579,5584 ****
--- 5570,5577 ----
  @cindex old pipeline description
  @cindex function units, for scheduling
  
+ @emph{Note:}The old pipeline description is deprecated.
+ 
  On most @acronym{RISC} machines, there are instructions whose results
  are not available for a specific number of cycles.  Common cases are
  instructions that load data from memory.  On many machines, a pipeline

Re: [doc] deprecate the old pipeline description

[Richard Henderson]

On Fri, Jul 09, 2004 at 05:50:48PM +0200, Steven Bosscher wrote:
> 	* md.texi (Processor pipeline description): Mention that the old
> 	pipeline description is deprecated.

This is fine.  Anyone writing new non-dfa descriptions may be smacked.


r~