Runtime: Clarify meaning of a flag bit in GenericWitnessTable

slavapestov · slavapestov · commit 6ebd9929ea3c · 2019-02-21T00:02:25.000-05:00
diff --git a/include/swift/ABI/Metadata.h b/include/swift/ABI/Metadata.h
@@ -2039,7 +2039,8 @@ struct TargetGenericWitnessTable {
     return WitnessTablePrivateSizeInWordsAndRequiresInstantiation >> 1;
   }
 
-  /// Whether the witness table is known to require instantiation.
+  /// This bit doesn't really mean anything. Currently, the compiler always
+  /// sets it when emitting a generic witness table.
   uint16_t requiresInstantiation() const {
     return WitnessTablePrivateSizeInWordsAndRequiresInstantiation & 0x01;
   }

Original file line number	Diff line number	Diff line change
`@@ -2039,7 +2039,8 @@ struct TargetGenericWitnessTable {`
`2039`	`2039`	`return WitnessTablePrivateSizeInWordsAndRequiresInstantiation >> 1;`
`2040`	`2040`	`}`
`2041`	`2041`
`2042`		`- /// Whether the witness table is known to require instantiation.`
	`2042`	`+ /// This bit doesn't really mean anything. Currently, the compiler always`
	`2043`	`+ /// sets it when emitting a generic witness table.`
`2043`	`2044`	`uint16_t requiresInstantiation() const {`
`2044`	`2045`	`return WitnessTablePrivateSizeInWordsAndRequiresInstantiation & 0x01;`
`2045`	`2046`	`}`