be: Factorise the code to emit an asm node and use a callback for each backend to output the operands.

Both functions do the same and the former is used way less.

create_compilerlib_entity() does it already, so it is not necessary to do it again in replace_with_call().

If this Conv is inserted, then the existing Conv becomes a nop.
So let the existing Conv handle the conversion.

Strange casts may cause that a Load ends up with a method entity to load from.

This prevented optimizing x < 0 ? -1 : 0, when the result is unsigned.

The same test is done by an enclosing if.

This simplifies to understand the pattern when reading the code.

It is a sign extension when the operand is signed, not just when both the operand and the result are signed.

This prevents accidently hitting a Switch, though this code can only handle Cond.
This code probably is older than the Cond-Switch schism and later tests removed switch-like Conds.

This typo was always there (even before Cmp relations), so this optimization never worked before.

It still assumed that Cmps have Projs.
Nobody noticed, because no -O level in cparser activates this optimization.