[llvm] [InstrRef] Skip clobbered EntryValue register recovery (PR #142478)

[Adrian Prantl via llvm-commits]

adrian-prantl wrote:

> * If the entry value is no longer available in any register, we take the `recoverAsEntryValue` path out of `loadVarInLoc`, produce a DBG_VALUE with an entry-value expression, and don't record anything to be tracked,

@jmorse Maybe we're using slightly different terminology here, but to me an entry value is not something that can be clobbered. It's an abstract concept that refers to a the value a register has at the beginning of a function that is divorced from the register inside the function. To an entry value of r0, it doesn't matter that r0 gets clobbered, because it doesn't refer to the *current* value of r0. That's why I think it makes more sense to treat *incoming* entry values similar to constants. They are not affected by clobbers.

https://github.com/llvm/llvm-project/pull/142478