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Prevent instructions from being instantiated with wrong operand types #8

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Prevent instructions from being instantiated with wrong operand types #8

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tpwrules
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Fixes issue #6 by preventing non-registers from being put in place of register operands and vice versa. Only checks and prevents this when instantiating the instructions directly.

x = MOVI(R0, 0) # legal
y = MOVI(0, 0) # non-reg where reg expected
z = MOVI(R0, R0) # reg where non-reg expected
x.rsd = 0 # legal
x.imm = R0 # legal
a = MOVI(Reg(0), int(R0)) # legal, converts between register number and register object

@whitequark
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This definitely won't work. For one, it introduces a circular dependency between mc and instr. Also, mc is supposed to be independent of any particular ISA.

@tpwrules
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Well, it worked great for me :)

I decided that this should only be checked for when instantiating instructions because someone who is setting attributes or constructing Reg and Imm objects (e.g. the assembler) probably knows what they're doing. Otherwise, the conditions could be checked for in prepare, except that there's not immediately a way to construct the initial register objects if prepare doesn't accept integers.

Maybe a validation function could be attached to instr.Instr.formats or be a class attribute/method of mc.Operand subclasses. Not sure what to call it though, is_legal_instantiation?

@whitequark whitequark closed this Nov 10, 2019
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@tpwrules @whitequark