#906: [PIR] Assignment syntactic sugar restricted to destination parameters
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Reporter: allison | Owner: kjs
Type: deprecation | Status: reopened
Priority: normal | Milestone: 2.6
Component: pirc | Version: 1.4.0
Severity: medium | Resolution:
Keywords: | Lang:
Patch: | Platform:
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Comment(by plobsing):
Replying to [comment:5 coke]:
> This points to a some cases where we have ops defined as, e.g.:
>
{{{
inline op mul(invar PMC, invar PMC, invar PMC) :base_core {
$1 = VTABLE_multiply(interp, $2, $3, $1);
}
}}}
>
> is invar the right declaration for $1 there?
It would be more correct to have that as inout (such errors would
seriously throw off any attempt at register allocation for example).
However, it still would not allow "$P0 = mul $P1, $P2" syntax, because the
op continues to use the LHS register as an input.
A workaround is that sugared unary and binary ops circumvent the check;
"$P0 = $P1 * $P2" (which gets translated to "mul $P0, $P1, $P2"), "$P0 =
5" (set $P0, 5), etc... do not trigger the assignment warning despite
treating the LHS as an input.
--
Ticket URL: <https://trac.parrot.org/parrot/ticket/906#comment:7>
Parrot <https://trac.parrot.org/parrot/>
Parrot Development
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