98 lines
3.6 KiB
Text
98 lines
3.6 KiB
Text
# $Id$
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This directory contains two programs:
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mkswitch:
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C program, necessary for regenerating the giant switch
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needed for the disassembly function of the interpreter,
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which (still) works with Operand access method 2
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(Intelligent Routines) as described in "The EM
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interpreter".
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mkiswitch:
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C program, necessary for regenerating the giant switch
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needed for finding the correct instruction handling routine
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for each opcode. It works with Operand access method 3
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(Intelligent Calls) as described in "The EM interpreter".
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It constructs the operand of the instruction and passes
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it to the appropriate routine with the operand as
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argument.
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The first program reads an input file which holds the interpreter
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opcode table (as shown in the [IR-81] report appendix B),
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and creates an output file which contains an enormous switch
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file. This switch has entries for each possible opcode. It's
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possible to supply a third filename, which is the name of file
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where all functions will be stored. This is necessary if a new
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function implementation is needed.
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The first argument to mkswitch is the prefix to be used in the
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generated function names. For the interpreter proper this prefix
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is Do.
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The input file contains lines in the following format:
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Mnemonic Flags Count First-number
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The created switch file will contain a switch, with each case
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having one of the following formats (? is the opcode):
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1) case ?: DoAz();
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2) case ?: DoBm(val);
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3) case ?: DoCs(hob, wsize);
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4) case ?: DoDXY(wsize);
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Ad 1) This format shows that the corresponding opcode does not
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have an argument. Often the operand is popped from the
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stack.
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e.g. DoNOPz(), this performs the NOP instruction.
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Ad 2) This is the format for a mini. There is one implicit
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argument (I) .
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e.g. DoLOCm(1), this is the LOC 1 instruction.
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Ad 3) This format corresponds with a shortie. There is an implicit
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argument (high order byte), and a one byte text argument
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(low order byte). W equals 'wsize' (if a word multiple),
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otherwise it equals '1'. H is the value of the high
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order byte.
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e.g. DoLOEs(2, wsize), these are all LOE instructions,
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with all addresses in the range:
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(512 * wordsize) . . (767 * wordsize).
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Ad 4) This format is used for opcodes with 2 or more text arguments,
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and no implicit arguments. There are 6 types:
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XY = l2: two byte negative or positive text argument.
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XY = n2: two byte negative text argument.
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XY = p2: two byte positive text argument.
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XY = l4: four byte negative or positive text argument.
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XY = n4: four byte negative text argument.
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XY = p4: four byte positive text argument.
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W equals 'wsize' (if a word multiple), otherwise it equals 1.
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e.g. DoLDLp2(wsize), these are all LDL instructions, with
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negative local offsets, which are word multiples.
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When two file arguments are given to mkswitch (input file and output file),
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only the switch is generated. If an additional third file name is
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given (another output file), this file is filled with all function
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calls in such a manner that mkfuncs will generate new function files.
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Mkfuncs expects two arguments, an input file generated by
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mkswitch and the name of a directory where the new function
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files are stored. These files (15) each represent one group (as
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proposed in [IR-81] sec 11.3) of instructions. Each file will
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contain all functions needed to implement that specific group
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of instructions. The functions will only contain a logging
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message, and a call to newPC() which is necessary to skip the
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arguments. The names of the generated files are: do_XXX.c, where
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XXX is the name of the corresponding instruction group.
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(Note: these remarks about mkfuncs are probably outdated now,
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since mkfuncs has disappeared. -rbf)
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