Copyright © 2001 by Edouard G. Parmelan
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
I had port JIT engine to Alpha Tru64 and GNU/Linux Alpha in the past and I know how it's difficult to understand correctly intrp and JIT engines with only sources as documentation. I had write this document latter while I was porting intrp engine to Darwin (Mac OS X) operating system. In the same time I was writing JIT back-end for PowerPC.
This document is written in SGML DocBook with GNU Emacs and PSGML major mode. Source of this document may be found in Kaffe CVS Tree or in my Kaffe repository.
If you find some bullets in this document, send an email to <egp@free.fr>. All comments are welcome. If you want to fix typo or grammar use SGML sources only and send me "diff -u" result. Never fill-paragraph NOR reformat them.
Preview current working draft here: http://egp.free.fr/port-kaffe/port-kaffe.html.
Others persons have already written documents on this subject. I some time peek phrases, sections or inspiration from them.
Kiyo Inaba, "What is trampoline code in Kaffe?", Aug 1998.
Kiyo Inaba, "How sysdepCallMethod works?", Jul 1998.
Samuel K. Sanseri <sanseri@cs.pdx.edu>, "Porting Kaffe to the IA-64 Architecture", Feb 2000.
The first step to port Kaffe to a new platform or new processor family is to port intrp engine. Then As soon as intrp engine works, you can port JIT engine (see Chapter 3). The biggest task will be to write JIT back-end for your processor family (see Chapter 4).
I will try to covers all these tasks in this document.
Quick presentation of all configuration files for a new platform.
Configuring unix-jthreads subsystem.
Locks subsystem.
Writing sysdepCallMethod() function.
Build intrp engine.
This shell script maps configure's variables $host_cpu and $host_os to Kaffe cananical forms $Khost_os and $Khost_os. These variables define access paths to cpu family and platform configuration files.
Optional Makefile fragments required for this cpu family.
Common definitions for all platforms of this cpu family.
Common thread definitions for all platforms of this cpu family.
configure's fragment for this platform.
It may holds specials $CFLAGS add-ons and cross-compile definitions.
Platform dependent header and functions.
File md.h typically includes $Khost_cpu/common.h and $Khost_cpu/thread.h and defines SP_OFFSET macro.
JIT/JIT3 definitions for this cpu family.
Platform JIT/JIT3 dependent header.
It includes $Khost_cpu/jit.h and defines EXCEPTIONPROTO and EXCEPTIONFRAME macros.
Fields inside classe objects must follow the alignment constraints of the C calling conventions. If alignment of type TYPE is not sizeof(TYPE) you must define macro ALIGNMENT_OF_SIZE(SIZE) in file config/$Khost_cpu/common.h.
The small C program developers/alignment_of_size.c may helps you to discover correct alignment. Simply compiles it and runs it.
Sources of threads subsystems are located into directory kaffe/kaffevm/systems/.
The common threads subsystem is unix-jthread. It uses setjmp() and longjmp() functions. In order to use it you must provide stack pointer offset into jmp_env.
The small C program developers/sp_offset.c may helps you to discover SP_OFFSET. Simply compiles it and runs it. It may leaves core file in you current directory.
Some platforms need to setup Frame-Pointer register when creating a new thread stack. In this case you must provide his offset FP_OFFSET into jmp_env.
Macros SP_OFFSET and FP_OFFSET should be defined in file config/$Khost_cpu/$Kost_os/md.h.
Define the macro THREADSTACKSIZE in file config/$Khost_cpu/thread.h to the size in bytes of each thread's stack. This size may depends on INTERPRETER defined as intrp engine will need greater stack size than JIT engine. Commun values are 64K for intrp engine and 32K for JIT engine.
You may want to use another threads subsystem specific to your platform. It is possible but it's not cover by this document. Read files FAQ/FAQ.jsignal and FAQ/FAQ.locks.
To select another threads subsystem, configure with option --with-threads=thread-subsystem.
Kaffe Fast Locking scheme (read FAQ/FAQ.locks) need a macro to atomic compare and exchange a lock address. This macro COMPARE_AND_EXCHANGE() must be implemented in assembler.
Macro COMPARE_AND_EXCHANGE() should be define in file config/$Khost_cpu/common.h. It is only used into file kaffe/kaffevm/locks.c.
If you can't implement it but have an atomic exchange instruction, defines macro ATOMIC_EXCHANGE() as in Sparc port.
Otherwise, fall back to plain C implementations as in MIPS I port. You should note that it will fail on a multi-processors machine.
Function sysdepCallMethod() setups standard registers and stack parameters for your ABI. It obeys to the C calling conventions of your platform.
It makes a call to a native or Java (JIT) method. This assembly code should build a standard C call using the passed call information. By its nature this is highly processor specific. This function is mandatory for both JIT and Interpreter (since stubs have now been deprecated).
It should be implemented in file config/$Khost_cpu/sysdepCallMethod.h.
The sysdepCallMethod() macro takes a single argument of type callMethodInfo* that describes where the parameters are, where the return value should go and what the signature of the method is.
The function sysdepCallMethod() is only used by functions callMethodA() and callMethodV() in file kaffe/kaffevm/support.c.
The followings macros control the construction of callMethodInfo structure. Define or not define some of them may help you to implements function sysdepCallMethod().
This define causes all types to occupy only one slot in callargs, but not affecting their callsizes, that can still be used to distinguish among types. It avoids introducing unused slots after jlongs and jdoubles.
NO_HOLES is incompatible with ALIGN_AT_64bits.
It causes all integer arguments to be promoted to jlong, and all jfloats to be promoted to jdouble, unless explicitly overridden. It implies NO_HOLES, unless explicitly defined otherwise.
If PROMOTE_jint2jlong is enabled, all integer values are to be passed as jlongs. It is only set by PROMOTE_TO_64bits.
If PROMOTE_jfloat2jdouble is enabled, jfloats are to be passed as jdoubles. Note that, when a jfloat is promoted, its calltype will be marked as 'D'. No known port uses this. In fact, alpha must explicitly set it to 0, to prevent PROMOTE_TO_64bits from enabling it.
This causes all 64bit arguments to be aligned at even arguments. If a jlong or jdouble appears as on odd argument, a place-holder will be introduced.
ALIGN_AT_64bits is incompatible with NO_HOLES.
The callMethodInfo structure describes the information necessary to invoke a native or just-in-time compiled method.
jvalue is a union defined in include/jtypes.h. It corresponds to an entry on the Java stack. The suffixes i, j, b, c, s, l, f, d access the corresponding element of (Java) type int, long, boolean, char, short, ref, float, and double.
args is an array containing the arguments passed to the function. It corresponds to the Java stack and has nrargs valid entries with the following property:
If two adjacent slots on the Java stack are combined to a 64bit value, it will also use two array entries, and not one. However, the first entry will contain the 64bit value (in j or d, depending on the type), and the second entry will be undefined. This allows for easier access, while preserving indexing. Thus, some array entries will have 0, some 32 and some 64 bits of valid data in them. The callsize array says which one it is.
callsize[i] may be 0, 1, or 2, depending on the number of valid bits in args[i]. Similarly, calltype[i] contains the signature type of the argument in args[i] ('J', 'F', etc.)
To simplify 32 bit assembly code, we copy the last 32 bits of a 64 bit arg into the next slot. This allows you to treat args as an array of 32 bit values. This simplification also makes a C version of sysdepCallMethod() more viable.
Note that "callsize[i] == 2 iff callsize[i+1] == 0" -- this property can also be exploited by function sysdepCallMethod().
function is a pointer to the method to be invoked.
retsize and rettype have the same value ranges as callsize[i] and calltype[i], except they correspond to the return value. The function sysdepCallMethod() must store the return value in the proper type at *ret.
If libffi handle your platform, you can use it to implements function sysdepCallMethod(). But it's better to implement it as described bellow.
Configure Kaffe with option --with-libffi explicitly in order to use libffi.
Kaffe use GNU libtool to build dynamic libraries and modules. If it is not able to create them, configure Kaffe with options --with-staticlib and --with-staticvm.
In order to port JIT engine, you must understand some parts of JIT engine.
Building stack trace.
Function trampoline.
If your platform use another C calling convensions (ABI) than those handled by JIT back-end of your cpu family you must change it to handle your ABI (see Chapter 4).
WRITE-ME: NullPointerException, ArithmeticException and signals.
WRITE-ME: buildStackTrace() and stack inspection.
WRITE-ME: retreiving lock object in a given stack frame.
WRITE-ME: method trampoline.
Before write new JIT back-end, Kaffe intrp engine must work on your platform (see Chapter 2).
To write new JIT back-end, you must implements the following files:
This file contains definitions for: exception handling, method dispatching, register management, opcode generation and slots management.
This file is the main implementation of the JIT back-end. It contains all back-end functions with special marker define_inst(function_name, internal_name).
This file contains definition of all JIT back-end functions. There are in fact macro HAVE_function_name define to back-end internal-name.
Function spill_TYPE() spills TYPE register seq_slot(0) into its assigned frame location offset seq_slot(1).
r = sreg_TYPE(0); o = const_int(1); $fp[o] = $r;
List of functions: spill_int(), spill_ref(), spill_long(), spill_float(), spill_double()
Function reload_TYPE() reloads TYPE register seq_slot(0) from given frame location offset seq_slot(1).
r = lreg_TYPE(0); o = const_int(1); $r = $fp[o];
List of functions: reload_int() reload_ref() reload_long() reload_float() reload_double()
Optional
Require macro HAVE_move_TYPE_const_rangecheck()
TODO
move_int_const() move_ref_const() move_long_const() move_float_const() move_double_const()
Optional
If not present, define functions move_label_const() and load_TYPE().
TODO
load_constpool_int() load_constpool_ref() load_constpool_long() load_constpool_double() load_constpool_float()
Optional
Require macro add_TYPE_const_rangecheck()
TODO
add_int_const() add_ref_const() add_long_const()
Optional
Require macro sub_TYPE_const_rangecheck()
TODO
sub_int_const() sub_ref_const() sub_long_const()
Optional
Required if sub_long() and sbc_int() are not implemented.
TODO
Optional
Require macro mul_TYPE_const_rangecheck()
TODO
mul_int_const() mul_long_const()
pusharg_TYPE() WRITE-ME: PUSHARG_FORWARDS kaffe/kaffevm/jni.c kaffe/kaffevm/jit3/icode.c
Source file developers/jit-icode.c may helps you to discover correct implementation of various JIT back-end functions. Compile it with -S option and read jit-icode.s or compile it with -g option and disassemble various functions with gdb or what ever debugger you have.
Script developers/kaffe-test.
Class VMDebug.
-vmdebug jit,morejit
Version 1.1, March 2000
Copyright (C) 2000 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
The purpose of this License is to make a manual, textbook, or other written document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.
This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you".
A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (For example, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.
The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.
The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.
A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, whose contents can be viewed and edited directly and straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modification by readers is not Transparent. A copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML designed for human modification. Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.
You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and you may publicly display copies.
If you publish printed copies of the Document numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a publicly-accessible computer-network location containing a complete Transparent copy of the Document, free of added material, which the general network-using public has access to download anonymously at no charge using public-standard network protocols. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.
You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:
Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has less than five).
State on the Title page the name of the publisher of the Modified Version, as the publisher.
Preserve all the copyright notices of the Document.
Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
Include an unaltered copy of this License.
Preserve the section entitled "History", and its title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
In any section entitled "Acknowledgements" or "Dedications", preserve the section's title, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
Delete any section entitled "Endorsements". Such a section may not be included in the Modified Version.
Do not retitle any existing section as "Endorsements" or to conflict in title with any Invariant Section.
If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.
You may add a section entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.
You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.
The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections entitled "History" in the various original documents, forming one section entitled "History"; likewise combine any sections entitled "Acknowledgements", and any sections entitled "Dedications". You must delete all sections entitled "Endorsements."
You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.
A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an "aggregate", and this License does not apply to the other self-contained works thus compiled with the Document, on account of their being thus compiled, if they are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.
You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.
To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:
Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. A copy of the license is included in the section entitled "GNU Free Documentation License".
If you have no Invariant Sections, write "with no Invariant Sections" instead of saying which ones are invariant. If you have no Front-Cover Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being LIST"; likewise for Back-Cover Texts.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.