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Shared: Explain SsaPhiNode a bit more.

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Geoffrey White
2024-02-29 15:45:43 +00:00
parent 8151f3024d
commit 98289b52d6
1 changed files with 12 additions and 1 deletions
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shared/rangeanalysis/codeql/rangeanalysis/RangeAnalysis.qll
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@@ -257,7 +257,18 @@ signature module Semantic {
/** /**
* A phi node in the SSA form. A phi node is a kind of node in the SSA form * A phi node in the SSA form. A phi node is a kind of node in the SSA form
* that represents a merge point where multiple control flow paths converge * that represents a merge point where multiple control flow paths converge
* and the value of a variable needs to be selected. * and the value of a variable needs to be selected according to which
* control flow path was taken. For example, in the following Ruby code:
* ```rb
* if b
* x = 0
* else
* x = 1
* end
* puts x
* ```
* A phi node for `x` is inserted just before the call `puts x`, since the
* value of `x` may come from either `x = 0` or `x = 1`.
*/ */
class SsaPhiNode extends SsaVariable { class SsaPhiNode extends SsaVariable {
/** Holds if `inp` is an input to the phi node along the edge originating in `bb`. */ /** Holds if `inp` is an input to the phi node along the edge originating in `bb`. */