[PATCH] D48305: [IR] Introduce helpers to skip meta-instructions

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

I don't think donothing counts as a meta-instruction, by your definition; yes, it has no effects and no operands, but it isn't ignored by the optimizer (it generally just gets erased, but that's not the same as ignoring it).

llvm.annotation and llvm.ptr.annotation have return values, so they can't be ignored by optimizations, in general.  llvm.var.annotation has a pointer operand, so it also can't be ignored by optimizations, in general.  This is intentional, so they can be used to experiment with new optimizations.

Given that, a "meta-instruction" is precisely debug info.  And I don't think that will change in the future.


https://reviews.llvm.org/D48305