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. \" $Id: i80.doc,v 2.6 1994/06/24 10:01:54 ceriel Exp $
.RP
.ND April 1985
.TL
Back end table for the Intel 8080 micro-processor
.AU
Gerard Buskermolen
.AB
A back end is a part of the Amsterdam Compiler Kit (ACK).
It translates EM, a family of intermediate languages, into the
assembly language of some target machine, here the Intel 8080 and Intel 8085 microprocessors.
.AE
.NH1
INTRODUCTION
.PP
To simplify the task of producing portable (cross) compilers and 
interpreters, the Vrije Universiteit designed an integrated collection
of programs, the Amsterdam Compiler Kit (ACK).
It is based on the old UNCOL-idea ([4]) which attempts to solve the problem
of making a compiler for each of
.B N
languages on
.B M
different machines without having to write
.B N\ *\ M
programs.
.sp 1
The UNCOL approach is to write
.B N
"front ends", each of which translates one source language into
a common intermediate language, UNCOL (UNiversal Computer Oriented
Language), and
.B M
"back ends", each of which translates programs in UNCOL into a
specific machine language.
Under these conditions, only
.B N\ +\ M
programs should be written to provide all
.B N
languages on all
.B M
machines, instead of
.B N\ *\ M
programs.
.sp 1
The intermediate language for the Amsterdam Compiler Kit is the machine
language for a simple stack machine called EM (Encoding Machine).
So a back end for the Intel 8080 micro translates EM code into
8080 assembly language.
.sp 1
The back end is a single program that is driven by a machine dependent
driving table.
This driving table, or back end table, 
defines the mapping from EM code to the machine's assembly language.
.NH 1
THE 8080 MICRO PROCESSOR
.PP
This back end table can be used without modification for the Intel 8085
processor.
Except for two additional instructions, the 8085 instruction set
is identical and fully compatible with the 8080 instruction set.
So everywhere in this document '8080' can be read as '8080 and 8085'.
.NH 2
Registers
.PP
The 8080 processor has an 8 bit accumulator,
six general purpose 8-bit registers,
a 16 bit programcounter and a 16 bit stackpointer.
Assembler programs can refer the accumulator by A and 
the general purpose registers by B, C, D, E, H and L. (*)
.FS
* In this document 8080 registers and mnemonics are referenced by capitals, for the sake of clarity.
Nevertheless the assembler expects small letters.
.FE
Several instructions address registers in groups of two, thus creating
16 bit registers:
.DS
Registers referenced:   Symbolic reference:
      B and C                   B
      D and E                   D
      H and L                   H
.DE
The first named register, contains the high order byte
(H and L stand for High and Low).
.br
The instruction determines how the processor interprets the reference.
For example, ADD B is an 8 bit operation, adding the contents of 
register B to accumulator A. By contrast PUSH B is a 16 bit operation
pushing B and C onto the stack.
.sp 1
There are no index registers.
.sp 1
.NH 2
Flip-flops
.PP
The 8080 microprocessor provides five flip-flops used as condition flags
(S, Z, P, C, AC) and one interrupt enable flip-flop IE.
.br
The sign bit S is set (cleared) by certain instructions when the most significant
bit of the result of an operation equals one (zero).
The zero bit Z is set (cleared) by certain operations when the
8-bit result of an operation equals (does not equal) zero.
The parity bit P is set (cleared) if the 8-bit result of an
operation includes an even (odd) number of ones.
C is the normal carry bit.
AC is an auxiliary carry that indicates whether there has been a carry
out of bit 3 of the accumulator.
This auxiliary carry is used only by the DAA instruction, which
adjusts the 8-bit value in the accumulator to form two 4-bit
binary coded decimal digits.
Needless to say this instruction is not used in the back-end.
.sp 1
The interrupt enable flip-flop IE is set and cleared under
program control using the instructions EI (Enable Interrupt) and
DI (Disable Interrupt).
It is automatically cleared when the CPU is reset and when
an interrupt occurs, disabling further interrupts until IE = 1 again.
.NH 2
Addressing modes
.NH 3
Implied addressing
.PP
The addressing mode of some instructions is implied by the instruction itself.
For example, the RAL (rotate accumulator left) instruction deals only with
the accumulator, and PCHL loads the programcounter with the contents
of register-pair HL.
.NH 3
Register addressing
.PP
With each instruction using register addressing,
only one register is specified (except for the MOV instruction),
although in many of them the accumulator is implied as
second operand.
Examples are CMP E, which compares register E with the accumulator,
and DCR B, which decrements register B.
A few instructions deal with 16 bit register-pairs:
examples are DCX B, which decrements register-pair BC and the 
PUSH and POP instructions.
.NH 3
Register indirect addressing
.PP
Each instruction that may refer to an 8 bit register, may
refer also to a memory location. In this case the letter M
(for Memory) has to be used instead of a register.
It indicates the memory location pointed to by H and L,
so ADD M adds the contents of the memory location specified
by H and L to the contents of the accumulator.
.br
The register-pairs BC and DE can also be used for indirect addressing,
but only to load or store the accumulator.
For example, STAX B stores the contents of the accumulator
into the memory location addressed by register-pair BC.
.NH 3
Immediate addressing
.PP
The immediate value can be an 8 bit value, as in ADI 10 which
adds 10 to the accumulator, or a 16 bit value, as in 
LXI H,1000, which loads 1000 in the register-pair HL.
.NH 3
Direct addressing
.PP
Jump instructions include a 16 bit address as part of the instruction.
.br
The instruction SHLD 1234 stores the contents of register
pair HL on memory locations 1234 and 1235.
The high order byte is stored at the highest address.
.NH 1
THE 8080 BACK END TABLE
.PP
The back end table is designed as described in [5].
For an overall design of a back end table I refer to this document.
.br
This section deals with problems encountered in writing the
8080 back-end table.
Some remarks are made about particular parts
of the table that might not seem clear at first sight.
.NH 2
Constant definitions
.PP
Word size (EM_WSIZE) and pointer size (EM_PSIZE) are both 
defined as two bytes.
The hole between AB and LB (EM_BSIZE) is four bytes: only the
return address and the local base are saved.
.NH 2
Registers and their properties
.PP
All properties have the default size of two bytes, because one-byte
registers also cover two bytes when put on the real stack.
.sp 1
The next considerations led to the choice of register-pair BC 
as local base.
Though saving the local base in memory would leave one more register-pair
available as scratch register, it would slow down instructions
as 'lol' and 'stl' too much.
So a register-pair should be sacrificed as local base.
Because a back-end without a free register-pair HL is completely
broken-winged, the only reasonable choices are BC and DE.
Though the choice between them might seem arbitrary at first sight,
there is a difference between register-pairs BC and DE:
the instruction XCHG exchanges the contents of register-pairs DE and
HL.
When DE and HL are both heavily used on the fake-stack, this instruction
is very useful.
Since it won't be useful too often to exchange HL with the local base
and since an instruction exchanging BC and HL does not exist, BC is
chosen as local base.
.sp 1
Many of the register properties are never mentioned in the
PATTERNS part of the table.
They are only needed to define the INSTRUCTIONS correctly.
.sp 1
The properties really used in the PATTERNS part are:
.IP areg: 24
the accumulator only
.IP reg:
any of the registers A, D, E, H or L. Of course the registers B and C which are
used as local base don't possess this property.
When there is a single register on the fake-stack, its value
is always considered non-negative.
.IP dereg:
register-pair DE only
.IP hlreg:
register-pair HL only
.IP hl_or_de:
register-pairs HL and DE both have this property
.IP local base:
used only once (i.e. in the EM-instruction 'str 0')
.PP
.sp 1
The stackpointer SP and the processor status word PSW have to be
defined explicitly because they are needed in some instructions
(i.e. SP in LXI, DCX and INX and PSW in PUSH and POP).
.br
It doesn't matter that the processor status word is not just register A
but includes the condition flags.
.NH 2
Tokens
.PP
The tokens 'm' and 'const1' are used in the INSTRUCTIONS- and MOVES parts only.
They will never be on the fake-stack.
.sp 1
The token 'label' reflects addresses known at assembly time.
It is used to take full profit of the instructions LHLD
(Load HL Direct) and SHLD (Store HL Direct).
.sp 1
Compared with many other back-end tables, there are only a small number of
different tokens (four).
Reasons are the limited addressing modes of the 8080 microprocessor,
no index registers etc.
For example to translate the EM-instruction
.DS
lol 10
.DE
the next 8080 instructions are generated:
.DS L
LXI H,10        /* load registers pair HL with value 10 */
DAD B           /* add local base (BC) to HL            */
MOV E,M         /* load E with byte pointed to by HL    */
INX H           /* increment HL                         */
MOV D,M         /* load D with next byte                */
.DE
Of course, instead of emitting code immediately, it could be postponed
by placing something like a {LOCAL,10} on the fake-stack, but some day the above
mentioned code will have to be generated, so a LOCAL-token is
hardly useful.
See also the comment on the load instructions.
.NH 2
Sets
.PP
Only 'src1or2' is used in the PATTERNS.
.NH 2
Instructions
.PP
Each instruction indicates whether or not the condition flags
are affected, but this information will never have any influence
because there are no tests in the PATTERNS part of the table.
.sp 1
For each instruction a cost vector indicates the number of bytes
the instruction occupies and the number of time periods it takes
to execute the instruction.
The length of a time period depends on the clock frequency
and may range from 480 nanoseconds to 2 microseconds on a 
8080 system and from 320 nanoseconds to 2 microseconds
on a 8085 system.
.sp 1
In the TOKENS-part the cost of token 'm' is defined as (0,3).
In fact it usually takes 3 extra time periods when this register indirect mode
is used instead of register mode, but since the costs are not completely
orthogonal this results in small deficiencies for the DCR, INR and MOV
instructions.
Although it is not particularly useful these deficiencies are
corrected in the INSTRUCTIONS part, by treating the register indirect
mode separately.
.sp 1
The costs of the conditional call and return instructions really
depend on whether or not the call resp. return is actually made.
However, this is not important to the behaviour of the back end.
.sp 1
Instructions not used in this table have been commented out.
Of course many of them are used in the library routines.
.NH 2
Moves
.PP
This section is supposed to be straight-forward.
.NH 2
Tests
.PP
The TESTS section is only included to refrain
.B cgg
from complaining.
.NH 2
Stacking rules
.PP
When, for example, the token {const2,10} has to be stacked while
no free register-pair is available, the next code is generated:
.DS
PUSH H
LXI H,10
XTHL
.DE
The last instruction exchanges the contents of HL with the value
on top of the stack, giving HL its original value again.
.NH 2
Coercions
.PP
The coercion to unstack register A, is somewhat tricky,
but unfortunately just popping PSW leaves the high-order byte in
the accumulator.
.sp 1
The cheapest way to coerce HL to DE (or DE to HL) is by using
the XCHG instruction, but it is not possible to explain
.B cgg
this instruction in fact exchanges the contents of these
register-pairs.
Before the coercion is carried out other appearances of DE and HL
on the fake-stack will be moved to the real stack, because in
the INSTRUCTION-part is told that XCHG destroys the contents
of both DE and HL.
The coercion transposing one register-pair to another one by
emitting two MOV-instructions, will be used only if
one of the register-pairs is the local base.
.NH 2
Patterns
.PP
As a general habit I have allocated (uses ...) all registers
that should be free to generate the code, although it is not
always necessary.
For example in the code rule
.DS
pat loe
uses hlreg
gen lhld {label,$1}                   yields hl
.DE
the 'uses'-clause could have been omitted because 
.B cgg
knows that LHLD destroys register-pair HL.
.sp 1
Since there is only one register with property 'hlreg',
there is no difference between 'uses hlreg' (allocate a
register with property 'hlreg') and 'kills hlreg' (remove
all registers with property 'hlreg' from the fake-stack).
The same applies for the property 'dereg'.
.br
Consequently 'kills' is rarely used in this back-end table.
.NH 3
Group 1: Load instructions
.PP
When a local variable must be squared, there will probably be EM-code like:
.DS
lol 10
lol 10
mli 2
.DE
When the code for the first 'lol 10' has been executed, DE contains the
wanted value.
To refrain 
.B cgg
from emitting the code for 'lol 10' again, an extra
pattern is included in the table for cases like this.
The same applies for two consecutive 'loe'-s or 'lil'-s.
.sp 1
A bit tricky is 'lof'.
It expects either DE or HL on the fake-stack, moves {const2,$1}
into the other one, and eventually adds them.
The 'kills' part is necessary here because if DE was on the fake-stack,
.B cgg
doesn't see that the contents of DE is destroyed by the code
(in fact 'kills dereg' would have been sufficient: because of the
DAD instruction 
.B cgg
knows that HL is destroyed).
.sp 1
By lookahead,
.B cgg
can make a clever choice between the first and
second code rule of 'loi 4'.
The same applies for several other instructions.
.NH 3
Group 2: Store instructions
.PP
A similar idea as with the two consecutive identical load instructions
in Group 1, applies for a store instruction followed by a corresponding load instruction.
.NH 3
Groups 3 and 4: Signed and unsigned integer arithmetic
.PP
Since the 8080 instruction set doesn't provide multiply and
divide instructions, special routines are made to accomplish these tasks.
.sp 1
Instead of providing four slightly differing routines for 16 bit signed or
unsigned division, yielding the quotient or the remainder,
the routines are merged.
This saves space and assembly time
when several variants are used in a particular program,
at the cost of a little speed.
When the routine is called, bit 7 of register A indicates whether
the operands should be considered as signed or as unsigned integers,
and bit 0 of register A indicates whether the quotient or the
remainder has to be delivered.
.br
The same applies for 32 bit division.
.sp 1
The routine doing the 16 bit unsigned multiplication could
have been used for 16 bit signed multiplication too.
Nevertheless a special 16 bit signed multiplication routine is
provided, because this one will usually be much faster.
.NH 3
Group 5: Floating point arithmetic
.PP
Floating point is not implemented.
Whenever an EM-instruction involving floating points is offered
to the code-generator, it calls the corresponding
library routine with the proper parameters.
Each floating point library routine calls 'eunimpl',
trapping with trap number 63.
Some of the Pascal and C library routines output floating point
EM-instructions, so code has to be generated for them.
Of course this does not imply the code will ever be executed.
.NH 3
Group 12: Compare instructions
.PP
The code for 'cmu 2', with its 4 labels, is terrible.
But it is the best I could find.
.NH 3
Group 9: Logical instructions
.PP
I have tried to merge both variants of the instructions 'and 2', 'ior 2' and 'xor 2',
as in
.DS
pat and $1==2
with hl_or_de hl_or_de
uses reusing %1, reusing %2, hl_or_de, areg
gen mov a,%1.2
    ana %2.2
    mov %a.2,a
    mov a,%1.1
    ana %2.1
    mov %a.1,a                     yields %a
.DE
but the current version of
.B cgg
doesn't approve this.
In any case
.B cgg
chooses either DE or HL to store the result, using lookahead.
.NH 3
Group 14: Procedure call instructions
.PP
There is an 8 bytes function return area, called '.fra'.
If only 2 bytes have to be returned, register-pair DE is used.
.NH 1
LIBRARY ROUTINES
.PP
Most of the library routines start with saving the return address
and the local base, so that the parameters are on the top of the stack
and the registers B and C are available as scratch registers.
Since register-pair HL is needed to accomplish these tasks,
and also to restore everything just before the routine returns,
it is not possible to transfer data between the routines and the
surrounding world through register H or L. 
Only registers A, D and E can be used for this.
.sp
When a routine returns 2 bytes, they are usually returned in 
registers-pair DE.
When it returns more than 2 bytes they are pushed onto the stack.
.br
It would have been possible to let the 32 bit arithmetic routines
return 2 bytes in DE and the remaining 2 bytes on the stack
(this often would have saved some space and execution time),
but I don't consider that as well-structured programming.
.NH 1
TRAPS
.PP
Whenever a trap, for example trying to divide by zero,
occurs in a program that originally was written in C or Pascal,
a special trap handler is called.
This trap handler wants to write an appropriate error message on the
monitor.
It tries to read the message from a file (e.g. etc/pc_rt_errors in the
EM home directory for Pascal programs), but since the 8080 back-end
doesn't know about files, we are in trouble.
This problem is solved, as far as possible, by including the 'open'-monitor call in the mon-routine.
It returns with file descriptor -1.
The trap handler reacts by generating another trap, with the original
trap number.
But this time, instead of calling the C- or Pascal trap handler again,
the next message is printed on the monitor:
.DS L
        trap number <TN>
        line <LN> of file <FN>

where   <TN> is the trap number (decimal)
        <LN> is the line number (decimal)
        <FN> is the filename of the original program
.DE
.sp 1
Trap numbers are subdivided as follows:
.IP 1-27: 20
EM-machine error, as described in [3]
.IP 63:
an unimplemented EM-instruction is used
.IP 64-127:
generated by compilers, runtime systems, etc.
.IP 128-252:
generated by user programs
.NH 1
IMPLEMENTATION
.PP
It will not be possible to run the entire Amsterdam Compiler Kit on a
8080-based computer system.
One has to write a program on another 
system, a system where the compiler kit runs on.
This program may be a mixture of high-level languages, such as 
C or Pascal, EM and 8080 assembly code.
The program should be compiled using the compiler kit, producing 8080 machine code.
This code should come available to the 8080 machine
for example by downloading or
by storing it in ROM (Read Only Memory).
.sp 1
Depending on the characteristics of the particular 8080 based system, some
adaptations have to be made:
.IP 1) 10 
In 'head_em': the base address, which is the address where the first
8080 instruction will be stored, and the initial value of the
stackpointer are set to 0x1000 and 0x8000 respectively.
.br
Other systems require other values.
.IP 2)
In 'head_em': before calling "__m_a_i_n", the environment
pointer, argument vector and argument count will have to be pushed
onto the stack.
Since this back-end is tested on a system without any knowledge
of these things, dummies are pushed now.
.IP 3)
In 'tail_em': proper routines "putchar" and "getchar" should
be provided.
They should write resp. read a character on/from the monitor.
Maybe some conversions will have to be made.
.IP 4)
In 'head_em': an application program returns control to the monitor by 
jumping to address 0xFB52.
This may have to be changed for different systems.
.IP 5)
In 'tail_em': the current version of the 8080 back-end has very limited I/O
capabilities, because it was tested on a system that
had no knowledge of files.
So the implementation of the EM-instruction 'mon' is very simple;
it can only do the following things:
.RS
.IP Monitor\ call\ 1: 40
exit
.IP Monitor\ call\ 3:
read, always reads from the monitor.
.br
echos the read character.
.br
ignores file descriptor.
.IP Monitor\ call\ 4:
write, always writes on the monitor.
.br
ignores file descriptor.
.IP Monitor\ call\ 5:
open file, returns file descriptor -1.
.br
(compare chapter about TRAPS)
.IP Monitor\ call\ 6:
close file, returns error code = 0.
.IP Monitor\ call\ 54:
io-control, returns error code = 0.
.RE
.sp
If the system should do file-handling the routine ".mon"
should be extended thoroughly.
.NH 1
INTEL 8080 VERSUS ZILOG Z80 AND INTEL 8086
.NH 2
Introduction
.PP
At about the same time I developed the back end
for the Intel 8080 and Intel 8085,
Frans van Haarlem did the same job for the Zilog z80 microprocessor.
Since the z80 processor is an extension of the 8080,
any machine code offered to a 8080 processor can be offered
to a z80 too.
The assembly languages are quite different however.
.br
During the developments of the back ends we have used
two micro-computers, both equipped with a z80 microprocessor.
Of course the output of the 8080 back end is assembled by an
8080 assembler. This should assure I have never used any of
the features that are potentially available in the z80 processor,
but are not part of a true 8080 processor.
.sp 1
As a final job, I have
investigated the differences between the 8080 and z80 processors
and their influence on the back ends.
I have tried to measure this influence by examining the length of
the generated code.
I have also involved the 8086 micro-processor in this measurements.
.NH 2
Differences between the 8080 and z80 processors
.PP
Except for some features that are less important concerning back ends,
there are two points where the z80 improves upon the 8080:
.IP First, 18
the z80 has two additional index registers, IX and IY.
They are used as in
.DS
         LD B,(IX+10)
.DE
The offset, here 10, should fit in one byte.
.IP Second,
the z80 has several additional instructions.
The most important ones are:
.RS
.IP 1) 8
The 8080 can only load or store register-pair HL direct
(using LHLD or SHLD).
The z80 can handle BC, DE and SP too.
.IP 2)
Instructions are included to ease block movements.
.IP 3)
There is a 16 bit subtract instruction.
.IP 4)
While the 8080 can only rotate the accumulator, the z80
can rotate and shift each 8 bit register.
.IP 5)
Special routines are included to jump to near locations, saving 1 byte.
.RE
.NH 2
Consequences for the 8080 and z80 back end
.PP
The most striking difference between the 8080 and z80 back ends
is the choice of the local base.
The writer of the z80 back end chose index register IY as local base,
because this results in the cheapest coding of EM-instructions
like 'lol' and 'stl'.
The z80 instructions that load local 10, for example
.DS
LD E,(IY+10)
LD D,(IY+11)
.DE
occupy 6 bytes and take 38 time periods to execute.
The five corresponding 8080 instructions loading a local
occupy 7 bytes and take 41 time periods.
Although the profit of the z80 might be not world-shocking,
it should be noted that as a side effect it may save some
pushing and popping since register pair HL is not used.
.sp 1
The choice of IY as local base has its drawbacks too.
The root of the problem is that it is not possible to add
IY to HL.
For the EM-instruction
.DS
lal 20
.DE
the z80 back end generates code like
.DS
LD BC,20
PUSH IY
POP HL
ADD HL,BC
.DE
leaving the wanted address in HL.
.br
This annoying push and pop instructions are also needed in some
other instructions, for instance in 'lol' when the offset
doesn't fit in one byte.
.sp 1
Beside the choice of the local base, I think there is no
fundamental difference between the 8080 and z80 back ends,
except of course that the z80 back end has register pair BC
and, less important, index register IX available as scratch registers.
.sp 1
Most of the PATTERNS in the 8080 and z80 tables are more or less
a direct translation of each other.
.NH 2
What did I do?
.PP
To get an idea of the quality of the code generated by
the 8080, z80 and 8086 back ends I have gathered
some C programs and some Pascal programs.
Then I produced 8080, z80 and 8086 code for them.
Investigating the assembler listing I found the
lengths of the different parts of the generated code.
I have checked two areas:
.IP 1) 8
the entire text part
.IP 2)
the text part without any library routine, so only the plain user program
.LP
I have to admit that neither one of them is really honest.
When the entire text part is checked, the result is disturbed
because not always the same library routines are loaded.
And when only the user program itself is considered, the result is
disturbed too.
For example the 8086 has a multiply instruction,
so the EM-instruction 'mli 2' is translated in the main program,
but the 8080 and z80 call a library routine that is not counted.
Also the 8080 uses library routines at some places where the
z80 does not.
.sp 1
But nevertheless I think the measurements will give an idea
about the code produced by the three back ends.
.NH 2
The results
.PP
The table below should be read as follows.
For all programs I have computed the ratio of the code-lengths
of the 8080, z80 and 8086.
The averages of all Pascal/C programs are listed in the table,
standardized to '100' for the 8080.
So the listed '107' indicates that the lengths
of the text parts of the z80 programs that originally were Pascal programs,
averaged 7 percent larger than in the corresponding 8080 programs.
.DS C
 --------------------------------------------------
|                       |  8080  |   z80  |  8086  |
 --------------------------------------------------
| C, text part          |   100  |   103  |    65  |
| Pascal, text part     |   100  |   107  |    55  |
| C, user program       |   100  |   110  |    71  |
| Pascal, user program  |   100  |   118  |    67  |
 --------------------------------------------------
.DE
.TE
The most striking thing in this table is that the z80 back end appears
to produce larger code than the 8080 back end.
The reason is that the current z80 back end table is
not very sophisticated yet.
For instance it doesn't look for any EM-pattern longer than one.
So the table shows that the preparations in the 8080 back end table
to produce faster code (like recognizing special EM-patterns
and permitting one byte registers on the fake-stack)
was not just for fun, but really improved the generated code
significantly.
.sp 1
The table shows that the 8080 table is relatively better
when only the plain user program is considered instead  of the entire text part.
This is not very surprising since the 8080 back end sometimes
uses library routines where the z80 and especially the 8086 don't.
.sp 1
The difference between the 8080 and z80 on the one hand and the 8086
on the other is very big.
But of course it was not equal game:
the 8086 is a 16 bit processor that is much more advanced than the
8080 or z80 and the 8086 back end is known to produce
very good code.
.bp
.B REFERENCES
.sp 2
.IP [1] 10
8080/8085 Assembly Language Programming Manual,
.br
Intel Corporation (1977,1978)
.IP [2]
Andrew S. Tanenbaum, Hans van Staveren, E.G. Keizer and Johan W. Stevenson,
.br
A practical tool kit for making portable compilers,
.br
Informatica report 74, Vrije Universiteit, Amsterdam, 1983.
.sp
An overview on the Amsterdam Compiler Kit.
.IP [3]
Tanenbaum, A.S., Stevenson, J.W., Keizer, E.G., and van Staveren, H.
.br
Description of an experimental machine architecture for use with block
structured languages,
.br
Informatica report 81, Vrije Universiteit, Amsterdam, 1983.
.sp
The defining document for EM.
.IP [4]
Steel, T.B., Jr.
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UNCOL: The myth and the Fact. in Ann. Rev. Auto. Prog.
.br
Goodman, R. (ed.), vol. 2, (1960), p325-344.
.sp
An introduction to the UNCOL idea by its originator.
.IP [5]
van Staveren, Hans
.br
The table driven code generator from the Amsterdam Compiler Kit
(Second Revised Edition),
.br
Vrije Universiteit, Amsterdam.
.sp
The defining document for writing a back end table.
.IP [6]
Voors, Jan
.br
A back end for the Zilog z8000 micro,
.br
Vrije Universiteit, Amsterdam.
.sp
A document like this one, but for the z8000.