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MSIS Terminating OOS Z-code Generation

IP.com Disclosure Number: IPCOM000103679D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 202K

Publishing Venue

IBM

Related People

Ekanadham, K: AUTHOR [+4]

Abstract

MSIS (Multisequencing a Single Instruction Stream) 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.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 33% of the total text.

MSIS Terminating OOS Z-code Generation

       MSIS (Multisequencing a Single Instruction Stream) 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.

      The requirement that instructions be scheduled in conceptual
sequence within a PE in MSIS can be overcome by virtualizing the name
of the Processor Elements and scheduling virtual PE in conceptual
sequence.  The instructions associated with a virtual PE is also
called a THREAD.  By virtualizing the names of the PEs and creating
PE-IDs or THREADS, the resulting schedule sequence within a given PE
may well be Out-Of-conceptual-Sequence (OOS).  The Z-CODE is called
OOS Z-CODE.

      The following algorithm defines and determines the DDI of each
instruction incrementally as the instructions are presented in
conceptual sequence.  The interrelations between the instructions
that set values of registers and the instructions that use those
values set.  This interrelationship can be formulated in terms of a
Directed Acyclic Graph, a DAG.  The nodes of the DAG are instructions
and the arcs represent interrelationships of set/use.
o    DETERMINING THE DDI
     The DAG can  be used to determine the dependency depth (DDI) of
each instruction.  The DDI corresponds to the cycle of decode of an
instruction when there are more PEs than instructions and corresponds
to th...