6.2: [CSE] Fix combine of type_value. #82700
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The instruction has no operands but has a param type. Hash and compare the type and the type and the param type. rdar://154652254
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@swift-ci please test |
tbkka
approved these changes
Jul 2, 2025
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Ouch. I'm glad we found this one. |
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Explanation: Fix a miscompile of value generics.
CSE deduplicates instructions, substituting one for another and deleting the other. When doing this, it must prove that the instructions are the same.
Previously, it was determining that two
type_valueinstructions were the same when they had the same type and the same operands. Buttype_valuehas no operands; instead, it has a second "param type", which refers to the value generic in the function signature. CSE was disregarding when twotype_values had different param types. The result was to replace one value generic with another.Here, this is fixed by considering the type and the param type both in hashing and equality checking.
Scope: Affects optimized code with value generics.
Issue: rdar://154652254
Original PR: #82696
Risk: Low, this is a narrow fix that only affects value generics.
Testing: Added test.
Reviewer: Meghana Gupta ( @meg-gupta ), Andrew Trick ( @atrick )