There are a lot of tasserts in low-level VM functions, such as those in vm_block.cpp and arith.cpp that mainly verify the TypeTags of slot values that should never change. The Linux "perf" tool detects many of these as being quite expensive - some low-level functions spend 10-15% of their time checking these tasserts.

This ticket is narrowly scoped to improve $group block processing performance by changing the few most-expensive tasserts to dasserts in vm_block.cpp (code introduced by the PM-3417 feature this ticket is part of), i.e. those that call allBools(). This will remove them from non-debug builds (--dbg=off).