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Scheduling Successive Interactions of a Loop in DIG Designs

IP.com Disclosure Number: IPCOM000105707D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 192K

Publishing Venue

IBM

Related People

Ekanadham, K: AUTHOR [+3]

Abstract

The scheduling of successive iterations of a loop without unrolling the code can be accomplished by retaining the loop but giving it a new tag and retaining the new scheduling positions relative to the multiple TAGS assigned.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 28% of the total text.

Scheduling Successive Interactions of a Loop in DIG Designs

      The scheduling of successive iterations of a loop without
unrolling the code can be accomplished by retaining the loop but
giving it a new tag and retaining the new scheduling positions
relative to the multiple TAGS assigned.

      MSIS is a uniprocessor organization in which a set of
processing elements (PEs) working in concert execute Segments of the
instruction stream.  The Segments are either P-Segments, normal
uniprocessor instruction stream portions, that are processed in the
E-MODE of MSIS and produce Z-Segments, or the Z-Segments that are
processed in Z-MODE by MSIS.  The main difference between E-MODE and
Z-MODE is that during E-MODE each PE sees all instructions in the
Segment and executes the ones that are assigned to it, but during
Z-MODE a PE only sees the instructions assigned to it.

      As all PEs see all instructions in E-MODE, each PE can create
the Z-CODE it will require to re-execute the Segment as a Z-Segment,
the Z-CODE being stored in the Z-CACHE, and associated with
instructions in the Z-CODE are S-LISTS and D-LISTS, as appropriate.
An S-LIST instructs the PE, in the Z-MODE, that one or more of the
source registers in an instruction assigned to it is set by another
instruction that is executed on another PE, an S-LIST is a receiving
obligation.  The D-LIST instructs the PE in the Z-MODE as to the
names of PEs that require the values of the register(s) that are
being set by an instruction that is assigned to it.  A D-LIST entry
is a sending obligation.

      The set of instructions assigned to a single PE can be further
delineated as THREADS.  A THREAD is a sequence of instructions in the
original conceptual order, and a Thread is associated with a register
file which is either real or virtual.  There are no sending or
receiving obligations between instructions within a THREAD, and the
THREAD is the smallest unit of aggregation of instructions from a
SEGMENT.

      Individual instructions, while executing, carry an indication
as to which SEGMENT, DECODER, and THREAD they belong.  The
information concerning the DECODER and THREAD is derived from the
Z-CODE itself.  The SEGMENT index is assigned sequentially at each
SEGMENT SWITCH.  Segment switches occur at points in the code where
the Z-SEGMENT terminates or where a Branch Wrong Guess has been
detected.

      MSIS HEM is a High End Machine design that uses multiple
decoders within a single processor in the place of separate processor
elements (PEs).  A single Instruction Processing Unit (IPU) executes
all instructions in MSIS HEM albeit through a multiplicity of
register files that are associated with the THREADS.  MSIS META HEM
is a Multiple Execution Thread Architecture that separates the
THREADS from the next higher aggregate of instructions.  Thus the
action of S-LIST and/or D-LIST entries within the Z-CODE activates
and deactivates the THREADS, and alternate...