Fuller information about the compiler is provided in the document
"IMP Compiler for M68000: Version 3"
by Hamish Dewar, CLAN Systems.
HELP Registers gives additional information about parameter passing conventions
Example commands
IMP MYPROG Compile MYPROG with default options
producing object file MYPROG.MOB
IMP PARSER-LIST Compile PARSER producing object file PARSER.MOB
and listing file PARSER.LIS
IMP NEW.IMP-NOCHECK-NODIAG Compile NEW.IMP to NEW.MOB
without checks and diagnostics
IMP PROG2-NOEDIT Compile PROG2 to PROG2.MOB
without calling the editor to correct faults
detected in the program
There are two types of parameter for the IMP command: file names and option selections. File names may be specified positionally or by keyword, while option selections are specified by keyword only. The format for the positional parameters is:
IMP <source> , <predefinition> / <object> , <listing>
the keywords being -PRE -OFILE -LFILE
There is only one obligatory parameter and that is the name of the IMP source program to be compiled. There is no default file-name extension for the source file-name. As a matter of personal preference, programmers may or may not choose to adopt the extension .IMP for IMP programs.
There are two output files which may be generated by the Compiler: the object file containing the compiled code and the listing file. By default, the names for these files are derived from the source file-name. The default names may be overridden by specifying alternative names, either positionally or by keyword.
For example, the generation of an object file may be suppressed in either of the forms:
IMP PROG2/:N or IMP-OFILE=:N PROG2
By default, the Compiler DOES generate an object file provided that no errors are detected during compilation.
If no name is provided explicitly, the name is derived from the source file-name (without the extension .IMP if present). The extension .MOB (for Motorola object) is applied to the object file-name.
The compiled code file is eligible for execution by citing the name (without extension) as a command verb at system command level. There is no linking stage after compilation; the object file is immediately executable.
For example:
IMP MYPROG | command to compile MYPROG MYPROG compiled: 115 statements (+ 38 comments) to 1220 bytes (+ 24) MYPROG | command to run MYPROG
-OFILE=<filename> produce object file with specified name
(the extension .MOB is added unless present already)
-OFILE=:N do not produce object file
-FORCE produce object file even if program faulty
By default the Compiler DOES NOT produce a listing. If one is required, it is requested either by including the keyword -LIST in the command or by specifying a file-name as the second output parameter or as the value for the keyword -LFILE.
If no name is provided explicitly, the name is derived from the source file-name (without the extension .IMP if present). The extension .LIS is applied to the listing file-name.
The listing file consists of the text of the source file with added line numbers, and any fault or warning messages produced during compilation. Line numbering runs from 1 at the start of the file and includes blank lines and comment lines. Lines in included files are numbered independently, with an ampersand as an indicator.
-LIST produce source file listing
-LFILE=<filename> send listing to specified file
(the extension .LIS is added unless already present)
-TT send listing to terminal
-MAP output information at end of each procedure, indicating
size of code, etc.
-LOG print statistics at end of compilation indicating number
of statements, atoms per statement, identifiers per
statement, time taken, etc.
To disable any individual check, use the indicated keyword prefixed by NO, for example -NOSTRASS
-ASS include unassigned check on full integers -STRASS include unassigned check on strings -SASS include unassigned check on 16-bit values -BASS include unassigned check on 8-bit values
Defaults: -ASS -STRASS -NOSASS -NOBASS
The unassigned check is implemented by standardising all newly declared variables to a fixed pattern which is an improbable integer value. The check is defaulted off for variables occupying less than 32 bits because there is a greater possibility of the special pattern occurring as a genuine value.
Note that almost all examples of the violations listed below which involve only literal operands are detected and rejected at compile-time rather than run-time.
-ARR include array bound checking -OVER include overflow check on addition/subtraction -CAP include capacity checking on assignment -STACK include stack over-run check
Defaults: -ARR -NOOVER -CAP -STACK
-NOCHECK suppress all checks apart from stack over-run -NOCHECK-NOSTACK suppress all checks
Run-time diagnostic control:
-DIAG generate basic procedure call diagnostics
-NODIAG disable all diagnostics
-LINE generate line-number diagnostics (implies -DIAG)
-MON generate variable monitoring diagnostics (ditto)
-TRACE generate code which allows the program to be executed
one line at a time
Default: -DIAG -LINE -MON -NOTRACE
Compiler limits:
-IDents=n allow for n user idents (default 1000)
(also controls the total lengths allowed for)
-KBytes=n allow for codesize nK (default 64k, max 128k)
Compile-time control:
-STRICT exclude use of non-standard features
-NONS enable warning-free use of non-standard features
-LOW enable use of low-level features
-VOL assume functions and predicates are volatile
-HALF -SHORT assume multiply and divide may be done half/short
-WARN enable soft warnings
-EDIT automatically transfer control to the standard editor
on detection of an error in the program.
Compilation resumes when the edit is closed (just
close at once if you do not want to correct the error).
Default: -NOSTRICT -NONONS -NOLOW -VOL -NOHALF -NOSHORT -WARN -EDIT
The IMP language implemented by the V3 Compiler is substantially the same as the Vax/VMS version as defined in the EUCSD Report "The IMP77 Language" (3rd Edition).
The main exclusions and differences from Vax/VMS IMP77 are summarised below.
A fuller account is given in the V3 documentation which also describes a number of language extensions.
. reals are limited to single-precision (32-bits) and the
implementation is by software
. procedures and functions passed as parameters must be in scope to the
procedure to which they are passed
. there is no built-in function TYPEOF
. untyped %name parameters are usable only to supply an address, not type
or length information; the built-in function SIZEOF is not applicable to
such parameters
. %name %function as variant for %map is not accepted
. %on %event * is not permitted as a way of trapping all events
. line-breaks after %and and %or are not ignored
. loops with a control clause after as well as before (ie an %until as well
as a %while or %for) are accepted, but with a Non-standard warning
. external references must appear at the outermost textual level, that
is, before the first %begin or in the main program block.
. the effect of %continue is to pass control to the head of the containing
loop, where any %while or %for control clause is tested; any %until
clause at the end of the loop is ignored.
. if no initial value is specified for an own variable, this means that it
is initially unassigned, NOT zero.
. the preferred way of initialising %name variables of all kinds is in the
form "==NIL". The earlier form "==0" is also accepted, with a warning.
. event 9 is used exclusively for end-of-input; file system errors are
signalled as event 3, and non-numeric input for READ as event 4.
. the Compiler is stricter about the ordering of statements than the Vax
IMP Compiler. The normal ordering in any block should be declarations,
then event trap if any, then instructions. It is acceptable for static
declarations (eg procedures and %own variable declarations) to be
interspersed among instructions, but the Compiler queries any dynamic
variable declarations which appear after instructions, and hard-faults
any which appear in a loop or after a sequence change.
Warnings are issued in a number of cases where it may be useful to have an indication of possible hazards at compile-time rather than run-time.
. All unused switch index values are reported
[add a switch label with index * - eg 'S(*):' - to eliminate]
. A report is made if the destination variable(s) in a string resolution
are not manifestly capacious enough to receive whatever might be assigned
to them.
[increase the length (to 255 if necessary) to eliminate]
The procedures listed below are available without specification.
%integer%map INTEGER(%integer a)
%real%map REAL(%integer a)
%string(*)%map STRING(%integer a)
%record(*)%map RECORD(%integer a)
%byte%map BYTE or BYTEINTEGER(%integer a)
%short%map SHORT or SHORTINTEGER(%integer a)
%mite%map MITE(%integer a)
%half%map HALF(%integer a)
%byte%map LENGTH(%string(*)%name s)
%byte%map CHARNO(%string(*)%name s, %integer n)
%integer%fn ADDR(%name n)
%string(1)%fn TOSTRING(%integer k)
%string(255)%fn SUBSTRING(%string(255) s, %integer from,to)
%integer%fn REM(%integer a,b)
%integer%fn MULDIV(%integer a,b,c)
%integer%fn INTPT(%real x)
%integer%fn INT(%real x)
%real%fn FRACPT(%real x)
%real%fn SQRT(%real x)
%integer%fn CPUTIME
!in milliseconds (since process creation)
%name NIL
%record%format EVENTFM(%byte event,sub, %short *, %integer extra,
%string(255) message)
%record(eventfm) EVENT
%const%integer NL
%const%string SNL
%integer%fn NEXTSYMBOL
%routine READSYMBOL(%name n)
%routine PRINTSYMBOL(%integer k)
%routine SKIPSYMBOL
%routine PRINTSTRING(%string(255) s)
%routine READ(%name n)
%routine WRITE(%integer m, n)
%routine PRINT(%real x, %integer n,m)
%routine PRINTFL(%real x, %integer n)
%routine NEWLINE
%routine NEWLINES(%integer i)
%routine SPACE
%routine SPACES(%integer i)
%routine SELECT INPUT(%integer n)
%routine SELECT OUTPUT(%integer n)
%routine CLOSE INPUT
%routine CLOSE OUTPUT
%routine SET INPUT(%integer pos)
!establish new active position for current input stream
! set input(0) resets to the beginning of a file
%routine SET OUTPUT(%integer pos)
!establish new active position for current output stream
! set output(0) resets to the beginning of a file
%routine RESET INPUT equivalent to SET INPUT(0)
%routine RESET OUTPUT equivalent to SET OUTPUT(0)
%integer%fn INSTREAM
%integer%fn OUTSTREAM
%routine OPEN INPUT(%integer n, %string(255) S)
!*selects N at present*
%routine OPEN OUTPUT(%integer n, %string(255) S)
!*selects N at present*
%string(255)%fn CLIPARAM
! returns the parameter string supplied with the command
! invoking the program
%routine PROMPT(%string(255) S)
There are a number of libraries available on the system which provide groups of related procedures for use in writing programs. In order to make use of these, it is necessary to include the relevant declarations in the source program. Also, when running the program, it may be necessary to INSTALL the related object file (see the general system information on Libraries).
Short files containing the relevant declarations for the main system libraries
are available for general use in the directory INC. These files may be
'included' in IMP programs by means of the %INCLUDE statement, for example,
INCLUDE "INC:UTIL.IMP".
The pre-prepared libraries make use of the general external linkage mechanism implemented for IMP. This allows external REFERENCES in one program to be matched up with external DEFINITIONS in another program or module. The linkage takes place automatically when the program is run.
In IMP, an external reference starts with the keyword %external and includes the keyword %spec after the type. For example:
%external %routine %spec INITIALISE(%integer case)
%external %integer %spec CURRENT DEVICE
External definitions start with the keyword %external. For example:
%external %routine INITIALISE(%integer case)
......
%end
%external %integer CURRENT DEVICE=2
These must appear in the source file before the main block (if any).
A program module containing external procedures or variables, and terminated by
endoffile, is compiled in the ordinary way, eg IMP MYLIB. Before the externals
it contains can be accessed, the compiled module must be installed by the
INSTALL command. The INSTALL command takes as parameter the name of a program
file (extension MOB assumed) -- or list of names separated by commas. For
example INSTALL MYLIB. The effect of installing a program file is to add all
the external names it contains to the external symbol table; the code of the
module is not loaded at this stage. Thereafter (until logoff) these names are
available for external linking, which is done automatically when a program
referencing any of the names is loaded. It is only necessary to re-install a
program file if a change is made to the external names it contains.
An external name is the identifier declared as external (standardised to space-free upper-case form) unless this is over-ridden by an alias, in which case the alias name is used instead (exactly as presented). Note that an alias over-rides the declared identifier, rather than providing an alternative to it.
In general, data formats and the mechanisms for passing parameters and function results are completely compatible between IMP and Pascal. This applies to full integers, reals, varying strings, records, and arrays.
IMP %name parameters are compatible with Pascal VAR parameters.
IMP predicates are compatible with Pascal Boolean functions .
The IMP %byte is storage compatible with the Pascal Char.
Integer subrange correspondence is as follows:
IMP Pascal
%short -32768..32767
%half 0..65535
%mite -128..127
%byte 0..255
Error reports are kept short to economise on screen space. For reports which relate to a particular component of a statement, the culprit is identified by a marker at the start of the component. Soft warnings are accompanied by a '?'
REPORT MEANING
Faulty form statement part indicated is syntactically faulty
Unknown atom lexical atom indicated is mis-spelt or unknown
Non-starter atom at the start of the statement is not a
possible statement introducer
Unknown name identifier indicated has not been declared
Duplicate identifier indicated has already been declared
Mismatch parameters in body of procedure do not match spec
Not variable operand in assignment context is not a variable
Not reference operand in pointer context is not a reference
Wrong type expression is of wrong type for context
Wrong class category of identifier is wrong for context
Not literal expression in literal context is not literal
No size inappropriate use of universal, or undefined, type
Inside out upper bound is less than lower
Endless loop literal %for loop cannot terminate
Out of range operand value is out of range
Too few args too few arguments are given for procedure call
Too many args too many arguments are given for procedure call
Not in loop %exit %or %continue is not within a loop construct
Not in routine %return is not within a routine
Not in fn/map %result is not within a function or map
Not in pred %true/%false is not within a predicate
Not in block instruction or dynamic declaration at level 0
%CYCLE missing %repeat encountered with no matching %cycle
%REPEAT missing %end reached with unmatched %cycle
%START missing %finish or %else encountered with no matching %start
%FINISH missing %end reached with unmatched %start
Extra %ELSE %else encountered matching earlier unconditional %else
%BEGIN missing %end encountered with no matching %begin or
procedure header
%END missing %end %of %program or %file reached with unmatched
%begin or procedure header
Result missing there is apparently a path to the end of a function,
map or predicate which does not specify a result
Not accessible instruction apparently cannot be executed (warning only)
<ident> void identifier is used before a value is assigned to it
(warning only)
Dubious usage statement is valid but peculiar
Out of order statement appears in incorrect order in block
(warning if benign)
Nonstandard <n> non-standard language feature (warning only)
Low level low-level language feature
<ident> missing forward label or specced identifier does not appear
in block
<ident>(?) missing
switch label to which there is an explicit jump
has not been specified
<n> extra values for <ident>
too many values for %const or %own array
<n> missing values for <ident>
too few values for %const or %own array
Faulty operand incorrect operand type for machine instruction
Wrong size operand is of incorrect size for machine instruction
Not supported facility not implemented
Reg not free! statement cannot be compiled for lack of a register
Out of reach! %const or literal string, record or array is not
within the range of the machine addressing capability
<ident> Out of reach!
call to procedure specified is not within the
range of the machine addressing capability
Internal error <n>!
compiler fault
In the case of programs which exceed 32k bytes in size, the compiler uses a number of techniques to avoid creating within-program references which breach the M68000 PC-relative addressing limitation of +-32k. There is a possibility in some cases that these do not succeed, leading to an 'out-of-reach' report. If a name is given in the report, it is that of a procedure which is too distant from one of its calls. If no name is given, the problem is access to a constant.
Disastrous errors
These reports relate to compiler limits being exceeded. They all cause compilation to be abandoned.
Program too big Total size of the compiled code and constants
exceeds the maximum allowed for (see Option -KBYTES)
Code space exhausted Size of the code for currently open blocks
exceeds the maximum allowed for
Identifiers too big Total length of all current identifiers exceeds
the maximum allowed for (see Option -IDENTS)
Too many identifiers Number of current identifiers exceeds the maximum
allowed for (see Option -IDENTS)
Too many levels Depth of textual nesting of blocks exceeds
the maximum permitted (8)
Too many literals Internal storage space for literals is exhausted
Input ended There is no %endofprogram or %endoffile statement
Too many nested includes There are more than three levels of nesting
. In the absence of floating-point hardware, all floating-point
operations are performed by software.
. Integer multiply and divide are also performed by software, although
a number of special cases are optimised.
. Full checking is expensive in both time and space. Developed programs
should be compiled with checks and diagnostics disabled.
Fullest optimisation is obtained by specifying:
-NOCHECK-NODIAG-NOSTACK-NOVOL
. Procedure and function calls are implemented with a minimum of overhead
so that they may be freely used without significant penalty in all but
the most time-critical contexts. The space-saving from making full use
of procedures and functions can be substantial.
view:imp printed on 01/03/89 at 16.07