The splitting pass uses its 'unlikelyExecuted' predicate to statically
decide which blocks are cold.
- Do not treat noreturn calls as if they are cold unless they are actually marked cold. This is motivated by functions like exit() and longjmp(), which are not beneficial to outline.
- Do not treat inline asm as an outlining barrier. In practice asm("") is frequently used to inhibit basic block merging; enabling outlining in this case results in substantial memory savings.
- Treat invokes of cold functions as cold.
As a drive-by, remove the 'exceptionHandlingFunctions' predicate, because it's
no longer needed. The pass can identify & outline blocks dominated by EH pads,
so there's no need to special-case __cxa_begin_catch etc.