59 lines
1.5 KiB
TeX
59 lines
1.5 KiB
TeX
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Step1: Optimize direct calls:
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Suppose we have a case-lambda as follows
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(case-lambda
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[<formals_0> <code_0>]
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[<formals_1> <code_1>]
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...
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[<formals_n> <code_n>])
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First, generate labels for every clause as well as a label for top
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(case-lambda <label>
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[<formals_0> <label_0> <code0_>]
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[<formals_1> <label_1> <code1_>]
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...
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[<formals_n> <label_n> <coden_>])
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Now everywhere there is a call to a closure bound variable:
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(funcall x args ...)
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We match on the labels of x:
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* If a matching label is found, we transform the call to
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(dircall <label_i> x args ...)
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* If no matching label is found, we transform the call to
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(dircall <label> x args ...)
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If we match on a case with ". rest" formals, we emit a call
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to "list" on the rest arguments because the label will be
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inside the code (after the rest-args are constructed).
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Step2: Eliminate passing arg-counts:
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All direct calls to inner labels do not require passing an argument
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count since it will not be used by the procedure.
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Step3: Eliminate useless case-lambda cases. (not important)
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For every label generated, determine whether it is actually used or
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not.
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We assume the main label unused until we find:
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* A reference to it in a closure that's not a dircall operator.
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* A reference to it as the target label to a dircall.
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We assume an inner label unused until we find:
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* A direct call to it.
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* The main label used.
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If a case-lambda has unused clauses, they can be eliminated.
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If a case-lambda has an unused main label, the dispatch can be
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eliminated.
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