[llvm] [TableGen] Use std::move instead of swap. NFC. (PR #81606)

[Jay Foad via llvm-commits]

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@@ -545,8 +545,8 @@ void GroupMatcher::optimize() {
     if (T != E)
       F = ++T;
   }
-  optimizeRules<GroupMatcher>(Matchers, MatcherStorage).swap(Matchers);
-  optimizeRules<SwitchMatcher>(Matchers, MatcherStorage).swap(Matchers);
+  Matchers = optimizeRules<GroupMatcher>(Matchers, MatcherStorage);
+  Matchers = optimizeRules<SwitchMatcher>(Matchers, MatcherStorage);
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jayfoad wrote:

No `std::move`s here since we would be moving from a temporary, and the compiler warns that this prevents copy elision.

https://github.com/llvm/llvm-project/pull/81606