Make inliner cycle detection a fallible process
The query `mir_callgraph_cyclic` is supposed to find _all_ callees that _may_ lead to a recursive call back to the given `LocalDefId`. But that query was built using a function which recurses through the call graph and tries to locally handle hitting the recursion limit during the walk. That is wrong. If the recursion limit is encountered, the set may be incomplete and thus useless. If we hit the recursion limit the only correct thing to do is bail.
Some benchmarks improve because for some functions we will bail out of the call graph walk faster. Some benchmarks regress because we do less inlining, but that is quite rare with the default recursion depth.
Originally I thought this might be a fix for https://github.com/rust-lang/rust/issues/131960, but it turns out that it is _actually_ a fix for https://github.com/rust-lang/rust/issues/146998.
bors
2848c2ebe9