[clang] [clang][dataflow] Cache getModeledFields (PR #180878)

[Jan Voung via cfe-commits]

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@@ -329,6 +335,9 @@ class DataflowAnalysisContext {
   // Fields modeled by environments covered by this context.
   FieldSet ModeledFields;
 
+  // Cache of modeled fields for each type, covered by this context.
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jvoung wrote:

No, I have not. It seemed like in the case of a cache hit, it would be very similar (one map lookup).

Otherwise, it seemed like the cache miss case was already expensive enough, that computing this eagerly wouldn't be much different (maybe you get better icache behavior since it's doing the same code all together, but there is still all the traversing through the record fields).

https://github.com/llvm/llvm-project/pull/180878