Fix swapped mergeIf arguments in no-else case in Dataflow IR#8282
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tlively merged 1 commit intoWebAssembly:mainfrom Feb 11, 2026
Merged
Fix swapped mergeIf arguments in no-else case in Dataflow IR#8282tlively merged 1 commit intoWebAssembly:mainfrom
tlively merged 1 commit intoWebAssembly:mainfrom
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tlively
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Feb 10, 2026
…mbly#8273) In doVisitIf, when an if has no else branch, the two state arguments passed to mergeIf were in the wrong order. This caused the phi node to pair the "condition true" value with the initial state and the "condition false" value with the after-if-true state.
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| mergeIf(afterIfTrueState, afterIfFalseState, condition, curr, locals); | ||
| } else { | ||
| mergeIf(initialState, afterIfTrueState, condition, curr, locals); | ||
| mergeIf(afterIfTrueState, initialState, condition, curr, locals); |
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Why does the order matter here? I can't figure that out either from the code or from the PR description, sorry.
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I think it's so that the phi value indices are the same for the ifTrue and ifFalse edges in both the if-end and if-else-end cases.
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I see, thanks, looks like mergeIf assumes the first is executed if the condition is true. Makes sense.
I opened #8299 to clarify.
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Summary
mergeIfarguments indoVisitIfwhen anifhas noelsebranchFixes #8273.
In the no-else case,
mergeIf(initialState, afterIfTrueState, ...)incorrectly paired the initial state (before the if body ran) with theifTruecondition and the after-if-true state with theifFalsecondition. The fix swaps the arguments tomergeIf(afterIfTrueState, initialState, ...), matching the convention used in the if-with-else case.Test plan
DataflowTest.IfNoElseMergeOrderGTest that builds a dataflow graph for an if-no-else function and verifies the phi node selects the correct values for each branch