[llvm] [MachineLICM] Give opportunity to analyze physregs for invariance. (PR #84779)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> Unless I misunderstand what you're suggesting, I believe it is not the same because `implicit $vg` cannot be ignored. The dependence on `$vg` is important when trying to determine whether the instruction can be hoisted. Any definition of it in the loop should stop hoisting from happening. In contrast, `isIgnorableUse` does not result in any check for loop invariance of a physical register, it would instead just ignore the implicit use and continue the analysis as if it never saw the implicit use.

OK, understood, thanks for the explanation!

https://github.com/llvm/llvm-project/pull/84779