ValueMapper: Disallow metadata mapping recursion through mapValue
This adds an assertion to maintain the property from r265273. When
Mapper::mapSimpleMetadata calls Mapper::mapValue, it should not find its
way back to mapMetadataImpl. This guarantees that mapSimpleMetadata is
not involved in any recursion.
Since Mapper::mapValue calls out to arbitrary materializers, we need to
save a bit on the ValueMap to make this assertion effective.
There should be no functionality change here. This co-recursion should
already have been impossible.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265276
91177308-0d34-0410-b5e6-
96231b3b80d8