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1b000b90c9
This commit modifies the representation of the AIR `switch_br` instruction to represent ranges in cases. Previously, Sema emitted different AIR in the case of a range, where the `else` branch of the `switch_br` contained a simple `cond_br` for each such case which did a simple range check (`x > a and x < b`). Not only does this add complexity to Sema, which we would like to minimize, but it also gets in the way of the implementation of #8220. That proposal turns certain `switch` statements into a looping construct, and for optimization purposes, we want to lower this to AIR fairly directly (i.e. without involving a `loop` instruction). That means we would ideally like a single instruction to represent the entire `switch` statement, so that we can dispatch back to it with a different operand as in #8220. This is not really possible to do correctly under the status quo system. This commit implements lowering of this new `switch_br` usage in the LLVM and C backends. The C backend just turns any case containing ranges entirely into conditionals, as before. The LLVM backend is a little smarter, and puts scalar items into the `switch` instruction, only using conditionals for the range cases (which direct to the same bb). All remaining self-hosted backends are temporarily regressed in the presence of switch range cases. This functionality will be restored for at least the x86_64 backend before merge.