The inlined-generic-function Reference Manual

Table of Contents

The inlined-generic-function Reference Manual

This is the inlined-generic-function Reference Manual, version 0.1, generated automatically by Declt version 3.0 "Montgomery Scott" on Mon Apr 19 16:29:18 2021 GMT+0.

1 Introduction

* Bringing the speed of Static Dispatch to CLOS --- Inlined-Generic-Function [[https://circleci.com/gh/guicho271828/inlined-generic-function][https://circleci.com/gh/guicho271828/inlined-generic-function.svg?style=svg]] [[https://travis-ci.org/guicho271828/inlined-generic-function][https://travis-ci.org/guicho271828/inlined-generic-function.svg?branch=master]] [[http://quickdocs.org/inlined-generic-function/][http://quickdocs.org/badge/inlined-generic-function.svg]] 

Generic functions are convenient but slow.  During the development we
usually want the full dynamic feature of CLOS. However, when we really need
a fast binary and do not need the dynamism, the dynamic dispatch in the
generic functions should be statically compiled away.

We propose a MOP-based implementation of fast inlined generic functions
dispatched in compile-time. The amount of work required to inline your
generic function is minimal. 

Empirical analysis showed that *the resulting code is up to 10 times
faster than the standard generic functions.*

Tested on SBCL and CCL.

* News

Thanks to the suggestion from *@phmarek*,
I decided to add a feature called =invalid-branch= which uses impl-specific
feature to *enable a static type checking*.
[[./invalid-branch.org][Read the doc!]]

*Added an additional usage note.*

* Usage

The example code here is in =t/playground.lisp=.

First, declare the generic function with =inlined-generic-function=
metaclass.  This metaclass is a subclass of
=standard-generic-function=. Therefore, unless you use its special feature,
it acts exactly the same as the normal generic functions.

#+BEGIN_SRC lisp
(defgeneric plus (a b)
  (:generic-function-class inlined-generic-function))
#+END_SRC

Define the methods as usual.

#+BEGIN_SRC lisp
(defmethod plus :around ((a number) (b number))
  (+ a b) ;; not a meaningful operation...
  (call-next-method))

(defmethod plus ((a fixnum) (b fixnum))
  (+ a b))
(defmethod plus ((a float) (b float))
  (+ a b))
#+END_SRC

Define a function which uses it.

#+BEGIN_SRC lisp
(defun func-using-plus (a b)
  (plus a b))
#+END_SRC

At this point the gf is not inlined.

#+BEGIN_SRC lisp
; disassembly for FUNC-USING-PLUS
; Size: 24 bytes. Origin: #x100A75A165
; 65:       488BD1           MOV RDX, RCX                     ; no-arg-parsing entry point
; 68:       488BFB           MOV RDI, RBX
; 6B:       488B059EFFFFFF   MOV RAX, [RIP-98]                ; #
; 72:       B904000000       MOV ECX, 4
; 77:       FF7508           PUSH QWORD PTR [RBP+8]
; 7A:       FF6009           JMP QWORD PTR [RAX+9]
#+END_SRC

Now its time to inline the gf. There's nothing different from inlining a normal function.
In order to inline the generic function, just declare it =inline= when you use it.

#+BEGIN_SRC lisp
(defun func-using-plus (a b)
  (declare (inline plus))
  (plus a b))
; disassembly for FUNC-USING-INLINED-PLUS
; Size: 323 bytes. Origin: #x1002C3BD45
; D45:       8D41F1           LEA EAX, [RCX-15]               ; no-arg-parsing entry point
; D48:       A80F             TEST AL, 15
; D4A:       755F             JNE L2
; .....
#+END_SRC

To see the actual compiler-macro expansion, use a function =inline-generic-function=.

#+BEGIN_SRC lisp
(let ((*features* (cons :inline-generic-function *features*)))
  (print (inline-generic-function '(plus a b))))

;; Inlining a generic function PLUS

(LET ((#:A1734 (1+ A)) (#:B1735 (1- B)))
  (EMATCH* (#:A1734 #:B1735)
    (((TYPE FLOAT) (TYPE FLOAT))
     (LET ((A #:A1734) (B #:B1735))
       (DECLARE (TYPE FLOAT A))
       (DECLARE (TYPE FLOAT B))
       (+ A B)
       (LET ((A #:A1734) (B #:B1735))
         (DECLARE (TYPE FLOAT A))
         (DECLARE (TYPE FLOAT B))
         (+ A B))))
    (((TYPE FIXNUM) (TYPE FIXNUM))
     (LET ((A #:A1734) (B #:B1735))
       (DECLARE (TYPE FIXNUM A))
       (DECLARE (TYPE FIXNUM B))
       (+ A B)
       (LET ((A #:A1734) (B #:B1735))
         (DECLARE (TYPE FIXNUM A))
         (DECLARE (TYPE FIXNUM B))
         (+ A B))))))
#+END_SRC

Since =ematch= from Trivia pattern matcher expands into thoroughly typed
dispatching code, a sufficiently smart compiler would compile =+= into
machine assembly, which is the case at least in SBCL.

** Automatic compile-time dispatching

If the code is inlined in a typed environment, smart compilers like sbcl can
detect certain branches are not reachable, thus removing the checks and
reducing the code size. This is equivalent to compile-time dispatch.
In the example below, the code for dispatching
FLOAT is removed.

#+BEGIN_SRC lisp
(defun func-using-inlined-plus-and-type-added (a b)
  " ; disassembly for FUNC-USING-INLINED-PLUS-AND-TYPE-ADDED
; Size: 29 bytes. Origin: #x10031E7788
; 88:       4801F9           ADD RCX, RDI                     ; no-arg-parsing entry point
; 8B:       488BD1           MOV RDX, RCX
; 8E:       48D1E2           SHL RDX, 1
; 91:       710C             JNO L0
; 93:       488BD1           MOV RDX, RCX
; 96:       41BB70060020     MOV R11D, 536872560              ; ALLOC-SIGNED-BIGNUM-IN-RDX
; 9C:       41FFD3           CALL R11
; 9F: L0:   488BE5           MOV RSP, RBP
; A2:       F8               CLC
; A3:       5D               POP RBP
; A4:       C3               RET
"
  (declare (inline plus))
  (declare (optimize (speed 3) (safety 0)))
  (declare (type fixnum a b))
  (plus a b))
#+END_SRC

If the types does not match, errors are signalled by =EMATCH=, 
which is consistent with the behavior of standard generic functions.

** Enabling Inlining Globally

Inlining is not globally enabled by default.
This is because the inlined code becomes obsoleted when the
generic function definition changes, and therefore
you generally do not want to make them inlined during the development.

It can be enabled globally 
by adding =:inline-generic-function= flag in
=*features*=, which is useful when you build a standalone binary.
When this feature is present, all inlinable generic functions
are inlined unless it is declared =notinline=.

#+BEGIN_SRC lisp
(push :inline-generic-function *features*)
#+END_SRC

** Benchmark Setting

We tested two generic functions, one of which is a
standard-generic-function, and another is an inlined-generic-function.

Both generic functions follow the definition below:

#+BEGIN_SRC lisp
(defgeneric plus (a b)
  [(:generic-function-class inlined-generic-function)])
(defmethod plus :around ((a number) (b number))
  (+ a b)
  (call-next-method))
(defmethod plus ((a fixnum) (b fixnum))
  (+ a b))
(defmethod plus ((a double-float) (b double-float))
  (+ a b))
#+END_SRC

We tested them with and without =inline= declaration, i.e., 

#+BEGIN_SRC lisp
(defun func-using-plus (a b)
  (declare (optimize (speed 3) (safety 0)))
  (plus a b))

(defun func-using-inlined-plus (a b)
  (declare (inline plus))
  (declare (optimize (speed 3) (safety 0)))
  (plus a b))
#+END_SRC

Thus, we have 4 configurations in total.  The experiment is run under AMD
Phenom II X6 processor 2.8GHz with SBCL 1.3.1 (launched by Roswell).
The benchmark function is shown below:

#+BEGIN_SRC lisp
(defvar *input* (iter (repeat 1000)
                     (collect (cons (random 100.0d0) (random 100.0d0)))
                     (collect (cons (+ 20 (random 100)) (+ 20 (random 100))))))
(defun benchmark ()
  (time (iter (for (a . b) in *input*)
              (func-using-normal-plus a b)))
  (time (iter (for (a . b) in *input*)
              (func-using-normal-inlined-plus a b)))
  (time (iter (for (a . b) in *input*)
              (func-using-plus a b)))
  (time (iter (for (a . b) in *input*)
              (func-using-inlined-plus a b))))
#+END_SRC

We first run the benchmark function 1000 times in order to calibrate the CPU cache.
We then run the gc and invoke the benchmark function once more.
We use the result of this final run in order to make sure the machine state is stabilized.

** Result

Since the difference in the runtime is relatively small due to the small
amount of computation, we consider the processor cycles only.  We found
that the cost of generic function invocation is considerably low when an
=inlined-generic-function= is invoked with =inline= declaration.

| metaclass and inline declaration       | processor cycles | consing |
|----------------------------------------+------------------+---------|
| standard-generic-function, not inlined |          742,285 |       0 |
| standard-generic-function, inlined     |          726,023 |       0 |
| inlined-generic-function, not inlined  |        7,865,080 | 523,760 |
| inlined-generic-function, inlined      |         *74,120* |       0 |

Note that the third case, where the =inlined-generic-function= is not
inlined, is slower than the normal generic function. This would be because
we use the non-standard metaclass for representing the generic function and
the normal optimization provided by the implementation is not performed.
However, this is not a problem because we consider the third case only takes
place during the development.

** Conclusion

We showed that ... well, anyway, this is not a paper. Enjoy!

** Dependencies

This library is at least tested on implementation listed below:

+ SBCL 1.3.1 on X86-64 Linux  3.19.0-39-generic (author's environment)

Also, it depends on the following libraries:

+ trivia by Masataro Asai ::
    NON-optimized pattern matcher compatible with OPTIMA, with extensible optimizer interface and clean codebase

+ closer-mop by Pascal Costanza ::
    Closer to MOP is a compatibility layer that rectifies many of the absent or incorrect CLOS MOP features across a broad range of Common Lisp implementations.

+ alexandria by  ::
    Alexandria is a collection of portable public domain utilities.

+ iterate by  ::
    Jonathan Amsterdam's iterator/gatherer/accumulator facility


* Usage Note

When you use this library as part of your system, *make sure that the method
definitions are re-evaluated in load-time*. This is necessary because the
inlining information for the method could be lost after the compilation, i.e.,
the FASL file does not keep the defmethod form that should be inlined later.

The only thing you need is:

#+BEGIN_SRC lisp
(eval-when (:compile-toplevel :load-toplevel :execute)
  (defmethod ...)
  ...)
#+END_SRC

* Installation

Quicklisp available.

** Author

+ Masataro Asai (guicho2.71828@gmail.com)

* Copyright

Copyright (c) 2015 Masataro Asai (guicho2.71828@gmail.com)


* License

Licensed under the LLGPL License.

2 Systems

The main system appears first, followed by any subsystem dependency.

2.1 inlined-generic-function

Author

Masataro Asai

Contact

guicho2.71828@gmail.com

License

LLGPL

Description

MOP implementation of the fast inlinable generic functions dispatched in compile-time

Version

0.1

Dependencies

• trivia
• closer-mop
• alexandria
• iterate
• introspect-environment

Source

inlined-generic-function.asd (file)

Components

• src/0.package.lisp (file)
• src/1.mop.lisp (file)
• src/2.compiler.lisp (file)
• src/3.invalid-branch.lisp (file)

3 Files

Files are sorted by type and then listed depth-first from the systems components trees.

3.1 Lisp

3.1.1 inlined-generic-function.asd

Location

inlined-generic-function.asd

Systems

inlined-generic-function (system)

3.1.2 inlined-generic-function/src/0.package.lisp

Parent

inlined-generic-function (system)

Location

src/0.package.lisp

Packages

• inlined-generic-function.impl
• inlined-generic-function

3.1.3 inlined-generic-function/src/1.mop.lisp

Dependency

src/0.package.lisp (file)

Parent

inlined-generic-function (system)

Location

src/1.mop.lisp

Exported Definitions

• inlined-generic-function (class)
• inlined-method (class)
• method-lambda-expression (method)
• (setf method-lambda-expression) (method)
• method-lambda-expression* (method)
• (setf method-lambda-expression*) (method)

Internal Definitions

break+ (macro)

3.1.4 inlined-generic-function/src/2.compiler.lisp

Dependency

src/1.mop.lisp (file)

Parent

inlined-generic-function (system)

Location

src/2.compiler.lisp

Exported Definitions

inline-generic-function (function)

Internal Definitions

• %call-method (function)
• %compile-generic-function (function)
• %compute-applicable-methods (function)
• %matcher-body (function)
• %matcher-clause (function)
• %matcher-pattern (function)
• *current-gf* (special variable)
• *current-inline-form* (special variable)
• compile-generic-function (function)
• dummy (generic function)
• improve-readability (function)
• inline-discriminating-function (function)
• lambda-list-atoms (function)
• reorder-to-precedence (function)
• specializer< (function)
• take-while (function)

3.1.5 inlined-generic-function/src/3.invalid-branch.lisp

Dependency

src/2.compiler.lisp (file)

Parent

inlined-generic-function (system)

Location

src/3.invalid-branch.lisp

Exported Definitions

• *invalid-branch-warning-level* (special variable)
• invalid-branch (function)

4 Packages

Packages are listed by definition order.

4.1 inlined-generic-function.impl

Source

src/0.package.lisp (file)

Use List

• inlined-generic-function
• introspect-environment
• iterate
• alexandria
• trivia.level2
• closer-common-lisp

Exported Definitions

*invalid-branch-warning-level* (special variable)

Internal Definitions

• %call-method (function)
• %compile-generic-function (function)
• %compute-applicable-methods (function)
• %matcher-body (function)
• %matcher-clause (function)
• %matcher-pattern (function)
• *current-gf* (special variable)
• *current-inline-form* (special variable)
• break+ (macro)
• compile-generic-function (function)
• dummy (generic function)
• improve-readability (function)
• inline-discriminating-function (function)
• lambda-list-atoms (function)
• reorder-to-precedence (function)
• specializer< (function)
• take-while (function)

4.2 inlined-generic-function

Source

src/0.package.lisp (file)

Nickname

inlined-gf

Used By List

inlined-generic-function.impl

Exported Definitions

• inline-generic-function (function)
• inlined-generic-function (class)
• inlined-method (class)
• invalid-branch (function)
• method-lambda-expression (generic function)
• method-lambda-expression (method)
• (setf method-lambda-expression) (method)
• (setf method-lambda-expression) (generic function)
• method-lambda-expression* (generic function)
• method-lambda-expression* (method)
• (setf method-lambda-expression*) (method)
• (setf method-lambda-expression*) (generic function)

5 Definitions

Definitions are sorted by export status, category, package, and then by lexicographic order.

5.1 Exported definitions

5.1.1 Special variables

Special Variable: *invalid-branch-warning-level*

A flag controlling the level of compile-time warning signaled when
compiling a call to INVALID-BRANCH.
This does not affect the behavior of INVALID-BRANCH, which always signals an error.

Package

inlined-generic-function.impl

Source

src/3.invalid-branch.lisp (file)

5.1.2 Functions

Function: inline-generic-function WHOLE &optional ENV

Returns an inlined form which is equivalent to calling the generic function.

Package

inlined-generic-function

Source

src/2.compiler.lisp (file)

Function: invalid-branch &optional MESSAGE

This function mark a specific part of the code to be invalid.
It MUST NOT be used in a valid code.

On supported implementations (currently SBCL only),
the compiler signals a warning,style-warning or error
(depending on the value of *INVALID-BRANCH-WARNING-LEVEL*)
when the compiler fails to eliminiate it as a dead-code.

This is useful to detect a specific kind of errors,
e.g. type errors, infinite loops, infinite recursion and so on.
When it happens, you should fix the code, add a type restriction etc.
in order to make it compile.

On unsupported implementations, this function has no compile-time effect and just signals an error.

Supported implementations:

SBCL:
This feature is tested against all patch versions in the latest minor version, as well as the most recent patches in the past two minor versions.

Package

inlined-generic-function

Source

src/3.invalid-branch.lisp (file)

5.1.3 Generic functions

Generic Function: method-lambda-expression OBJECT

Generic Function: (setf method-lambda-expression) NEW-VALUE OBJECT

Package

inlined-generic-function

Methods

Method: method-lambda-expression (INLINED-METHOD inlined-method)

Method: (setf method-lambda-expression) NEW-VALUE (INLINED-METHOD inlined-method)

original lambda expression w/o decoration e.g. call-next-method

Source

src/1.mop.lisp (file)

Generic Function: method-lambda-expression* OBJECT

Generic Function: (setf method-lambda-expression*) NEW-VALUE OBJECT

Package

inlined-generic-function

Methods

Method: method-lambda-expression* (INLINED-METHOD inlined-method)

Method: (setf method-lambda-expression*) NEW-VALUE (INLINED-METHOD inlined-method)

Cached result of make-method-lambda

Source

src/1.mop.lisp (file)

5.1.4 Classes

Class: inlined-generic-function ()

A metaobject representing inlinable generic function.

Package

inlined-generic-function

Source

src/1.mop.lisp (file)

Direct superclasses

standard-generic-function (class)

Direct methods

• ensure-generic-function-using-class (method)
• make-method-lambda (method)

Direct Default Initargs

Initarg	Value
:method-class	(find-class (quote inlined-generic-function:inlined-method))

Class: inlined-method ()

A metaobject representing inlinable method.

Package

inlined-generic-function

Source

src/1.mop.lisp (file)

Direct superclasses

standard-method (class)

Direct methods

• make-method-lambda (method)
• method-lambda-expression* (method)
• method-lambda-expression* (method)
• method-lambda-expression (method)
• method-lambda-expression (method)

Direct slots

Slot: lambda-expression

original lambda expression w/o decoration e.g. call-next-method

Initargs

:method-lambda-expression

Readers

method-lambda-expression (generic function)

Writers

(setf method-lambda-expression) (generic function)

Slot: lambda-expression*

Cached result of make-method-lambda

Initargs

:method-lambda-expression*

Readers

method-lambda-expression* (generic function)

Writers

(setf method-lambda-expression*) (generic function)

5.2 Internal definitions

5.2.1 Special variables

Special Variable: *current-gf*

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Special Variable: *current-inline-form*

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

5.2.2 Macros

Macro: break+ &rest ARGS

Package

inlined-generic-function.impl

Source

src/1.mop.lisp (file)

5.2.3 Functions

Function: %call-method ARGS METHOD MORE-METHODS SPECS

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: %compile-generic-function GF ARGS WHOLE

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: %compute-applicable-methods GF SPECIALIZERS

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: %matcher-body GENSYMS GF M METHOD-COMBINATION SPECIALIZERS WHOLE

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: %matcher-clause GENSYMS GF METHOD-COMBINATION WHOLE ARGUMENT-PRECEDENCE-ORDER LAMBDA-LIST METHODS

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: %matcher-pattern LAMBDA-LIST ARGUMENT-PRECEDENCE-ORDER SPECIALIZERS

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: compile-generic-function GF ARGS ENV WHOLE

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: improve-readability FORM

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: inline-discriminating-function *CURRENT-INLINE-FORM* ARGS FORM SPECS

Corresponds to compute-discriminating-function in AMOP

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: lambda-list-atoms LAMBDA-LIST

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: reorder-to-precedence LAMBDA-LIST PRECEDENCE-ORDER SPECIALIZERS &aux LAMBDA-ATOMS

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: specializer< LAMBDA-LIST PRECEDENCE-ORDER M1 M2

return true if some specializer of m1, checked in an precedence order, is a subtype of the specializer of m2

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Function: take-while PRED LST

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

5.2.4 Generic functions

Generic Function: dummy ()

Package

inlined-generic-function.impl

Source

src/2.compiler.lisp (file)

Appendix A Indexes

A.1 Concepts

A.2 Functions

A.3 Variables

A.4 Data types