ffbbfbffce
This rewrite was introduced in #5676 and then reverted in #5682 due to a footgun
where we accidentally weren't actually checking the `y == !z` precondition. This
commit fixes the precondition check. It also fixes the arithmetic to be
correctly masked to the value type's width.
This reverts commit 268f6bfc1d.
This crate contains the core Cranelift code generator. It translates code from an intermediate representation into executable machine code.