An Overview of the SUIF2 System

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An Overview of the SUIF2 System

• Monica Lam
• Stanford University
• http//suif.stanford.edu/

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The SUIF System
PGI Fortran
Java
EDG C
EDG C
OSUIF
Interprocedural Analysis Parallelization Locality
Opt

SUIF2
Scalar opt Inst. Scheduling Register Allocation
C
MachSUIF
Alpha
x86
C OSUIF to SUIF is incomplete
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Overview of SUIF Components (I)
Basic Infrastructure Extensible IR and
utilities Hoof Suif object specification
lang Standard IR Modular compiler system
Pass submodule Data structures (e.g. hash
tables)
FE PGI Fortran, EDG C/C, Java SUIF1 / SUIF2
translators, S2c Interactive compilation
suifdriver Statement dismantlers SUIF IR
consistency checkers Suifbrowser, TCL visual
shell Linker
Object-oriented Infrastructure OSUIF
representation
Java OSUIF -gt SUIF lowering object layout and
method dispatch
Backend Infrastructure MachSUIF program
representation Optimization framework

Scalar optimizations common subexpression
elimination deadcode elimination peephole
optimizations Graph coloring register
allocation Alpha and x86 backends
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Overview of SUIF Components (II)
High-Level Analysis Infrastructure Graphs,
sccs Iterated dominance frontier Dot graph
output Region framework Interprocedural
analysis framework Presburger
arithmetic (omega) Farkas lemma Gaussian
elimination package
Intraprocedural analyses copy propagation
deadcode elimination Steensgaards alias analysis
Call graph Control flow graphs Interprocedural
region-based analyses array dependence
privatization scalar reduction
privatization Interprocedural parallelization Affi
ne partitioning for parallelism locality
unifies unimodular transform
(interchange, reversal, skewing) fusion,
fission statement reindexing and
scaling Blocking for nonperfectly nested loops
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Motivation for Extensible IR

• Suif1 design
• A fixed set of flat C classes
• All codes must change if we add new IR nodes
• e.g. printing objects, reading and writing to
  file
• Higher level semantic objects
• OSUIF (for object-oriented programming)
• Verilog event-driven control flow semantics
• Saturated arithmetic used in multimedia
  instruction sets
• Program analysis concepts
• Phi nodes in SSA analysis
• Synchronization operations introduced by
  parallelization
• Results of analysis

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Concept I Reflective IR

• Metaclass captures representation of IR nodes in
  a data structure
• Enables common generic routines to implement
• Persistence reading/writing to disk
• Cloning routine that copies the data structure
• Printing a generic routine to print out the
  information
• Walkers, iterators, visitors

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Concept IIObject hierarchy virtual aggregate
fields
ExecutionObject
Statement
get_child_statements
IfStatement
WhileStatement
get_then_part get_else_part
get_body

• Abstract names to refer to fundamental concepts
  in subclasses
• e.g. Statementget_child_statements at Statement
  level
• IfStatement get_then_part and get_else_part, or
• WhileStatement get_body
• Allows a pass to run on representation with
  extended semantics without recompilation
• e.g. Reuse a dead code elimination on SPMD code
  without recompilation

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Concept III Multiple Representations for
High-Level Analyses

• Multiple representations for different semantic
  levels
• e.g. FOR loops versus basic blocks in a control
  flow graph
• gt Alternative representations
• Mixture of high-level and low-level constructs
• Dismantlers lower the representation

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Concept IV High-level object specification
Insulates user from details
Object Definition (.hoof)
SUIF Macro Generator a general grammar-based tool
Meta-Class System reading writing to file in
machine-independent format
Interface for user (.h) Implementation in
Meta-Class System (.cpp)

• Easy for the programmer
• Easy for the implementor to develop the system

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Example of a Hoof Definition
C
class New public SuifObject public int
get_x() void set_x(int the_value)
New() void print() static const Lstring
get_class_name()
hoof
concrete New int x

• Uniform data access functions (get_ set_)
• Automatic generation of meta class information
  etc.

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Examples of Suif Nodes

• abstract Statement ExecutionObject
• virtual listltStatement ownergt
  child_statements
• ...
• concrete IfStatement Statement
• Expression condition in source_ops
• Statement owner then_part in
  child_statements
• Statement owner else_part in
  child_statements

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Motivation for a Modular Compiler System

• SUIF1
• All passes read and write suif files more
  modular and supportive of experimentation
• but it is slow
• Data between passes are written out as
  annotations
• Annotations must be expressed as strings when
  written out
• Requires manual pickling of annotations
• Nontrivial effort to support any interactivity

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SUIF2Concept I A Modular Compiler Architecture
MODULES
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Components

• Kernel provides all basic functionality
• iokernel implements I/O
• suifkernel hides iokernel and provides modules
  support, cloning, command line parsing, list of
  factories, etc.
• Modules
• passes provides a pass framework
• IR basic program representations
• Suifdriver
• provides execution control over modules and passes

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Concept II Dynamic Registration Interactive
Compilation

• Each module (a C class) has a unique
  module_name
• A DLL (dynamically linked library) has one or
  more modules
• Register its modules dynamically (init_ltdllnamegt)
• An interactive SUIF compiler
• gt suifdriver
• suifgt require basicnodes suifnodes
• suifgt require mylibrary
• suifgt load test.suif
• suifgt mylibrary_pass1
• suifgt print test.out
• suifgt save test.tsuif
• The Suifdriver
• has a set of pre-registered modules (require,
  load, print, save)
• imports libraries dynamically which can register
  new modules (new commands)
• System can be used for demand-driven program
  analysis.

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Memory/Memory vs File/File Passes
COMPILER
A driver that imports applies modules to
program in memory
A series of stand-alone programs
Suif-file1
Suif-file1
drivermodule1
Suif-file2
Suifdriver imports/executes module1 module2
module3
drivermodule2
Suif-file3
drivermodule3
Suif-file4
Suif-file4
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Concept III Easy to write a new analysis
subclass of a pass module
Executable
suifdriver
IR
Passes
suifnodes
analyses optimizations
basicnodes
Kernel
suifkernel
iokernel
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Example Pass Constant Folding of Procedures

• class mypass public Pass
• public
• mypass(SuifEnv env, const Lstring name)
  Pass(env, name)
• virtual mypass()
• Module clone() const return(Module) this
• void do_procedure_definition (ProcedureDefinition
  proc_def)
• if (is_kind_ofltStatementgt(proc_def-gtget-body())
  
• fold_statements(proc_def-gtget_body())
• extern C void init_mypass (SuifEnv suif_env)
• suif_env-gtget_module_subsystem()-gtregister_module
  
• (new mypass (suif_env, mypass))

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Research Infrastructure Support at 3 Levels

• I. Compose compiler with existing passes
• Dynamic composition of different passes
• II. Develop new passes
• User concentrates on algorithmic issues
• Infrastructure provides common functionalities
• Write code once, can run on SUIF program in
  memory or a file
• III. Develop new IR
• High-level specification of the IR nodes
• Old code works with new IR without recompilation

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Status

• Base infrastructures are solid
• System getting populated with interesting
  analyses
• End of NCI project PGI will no longer provide
  support
• Relies on community effort

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Stanford Team

• Gerald Aigner
• Gerald Cheong
• Amer Diwan
• Andrew Fikes
• David Heine
• Monica Lam
• Amy Lim
• Vladimir Livshits
• Virendra Mehta
• Brian Murphy
• Costa Sapuntzakis
• Christopher Unkel
• Hansel Wan
• Christopher Wilson