Browse Prior Art Database

Multisequencing a Single Instruction Stream Identifying Dead Registers in the Common Virtual Register File

IP.com Disclosure Number: IPCOM000104445D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 214K

Publishing Venue

IBM

Related People

Ekanadham, K: AUTHOR [+3]

Abstract

Multisequencing a Single Instruction Stream (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.

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This is the abbreviated version, containing approximately 26% of the total text.

Multisequencing a Single Instruction Stream Identifying Dead Registers in the Common Virtual Register File

      Multisequencing a Single Instruction Stream (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.

      The sequence of instructions that comprise a THREAD are in
conceptual sequence but THREADS can be interdigitated to form DECODER
STREAMS - the sequence of instructions that are issued by a single
DECODER.  Such a Z-CODE is called Out-Of-Sequence (OOS) Z-CODE.

      The LC or Level of Conditionality is essentially the number
branches, entry points, and serializers, that precede a given
instruction.  A recovery to a LC is attempted when a branch has been
guessed incorrectly and a wrong putative instruction stream has been
pursued.  Recovery is done through a ZZT-FRAME which monitors the
registers changed at each LC and via a scanning mechanism established
the correct machine state.  In the case of failed serialization a
similar recovery is required.  To avoid the effects of partial branch
groups that arise when an entry into a Z-SEGMENT is within a branch
group, these entry point can also increment the LC of the
instructions which follow them.  Adding LC classes does not alter the
operation of the state recovery as recovery is always made to the LC
of the branch or serializer that needs such recover...