Optimizer: add simplifications for checked_cast_br and unchecked_ref_cast #66763
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…cast Look through `upcast` and `init_existential_ref` instructions and replace the operand of this cast instruction with the original value. For example: ``` %2 = upcast %1 : $Derived to $Base %3 = init_existential_ref %2 : $Base : $Base, $AnyObject checked_cast_br %3 : $AnyObject to Derived, bb1, bb2 ``` This makes it more likely that the cast can be constant folded because the source operand's type is more accurate. In the example above, the cast reduces to ``` checked_cast_br %1 : $Derived to Derived, bb1, bb2 ``` which can be trivially folded to always-succeeds. Found while looking at `_SwiftDeferredNSDictionary.bridgeValues()`
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Look through
upcastandinit_existential_refinstructions and replace the operand of this cast instruction with the original value. For example:This makes it more likely that the cast can be constant folded because the source operand's type is more accurate. In the example above, the cast reduces to
which can be trivially folded to always-succeeds.
Found while looking at
_SwiftDeferredNSDictionary.bridgeValues()