51a3bd919d
This is a follow up change to eliminating uselists for ConstantData. In the previous revision, ConstantData had a replacement reference count instead of a uselist. This reference count was misleading, and not useful in the same way as it would be for another value. The references may not have even been in the current module, since these are shared throughout the LLVMContext. This doesn't space leak any more than we previously did; nothing was attempting to garbage collect unused constants. Previously the use_empty, and hasNUses type of APIs were supported through the reference count. These now behave as if the uses are always empty. Ideally it would be illegal to inspect these, but this forces API complexity into quite a few places. It may be doable to make it illegal to check these counts, but I would like there to be a targeted fuzzing effort to make sure every transform properly deals with a constant in every operand position. All tests pass if I turn the hasNUses* and getNumUses queries into assertions, only hasOneUse in particular appears to hit in some set of contexts. I've added unit tests to ensure logical consistency between these cases
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