LocalRef is an optimization pass for the SSA IntermediateLanguage, invoked from SSASimplify.
Description
Implementation
Details and Notes
Moving a global ref requires the Multi analysis, because a global ref can only be moved into a function that is executed at most once.
Conversion of non-escaping ref-s is structured in three phases:
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analysis — a variable r = Ref_ref x escapes if
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r is used in any context besides Ref_assign (r, _) or Ref_deref r
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all uses r reachable from a (direct or indirect) call to Thread_copyCurrent are of the same flavor (either Ref_assign or Ref_deref); this also requires the Multi analysis.
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transformation
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rewrites r = Ref_ref x to r = x
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rewrites _ = Ref_assign (r, y) to r = y
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rewrites z = Ref_deref r to z = r
Note that the resulting program violates the SSA condition.
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Restore — restore the SSA condition.