[Yhc] bytecode more complex than needed?

[Tom Shackell]

Indeed it could :-)

It's almost certainly like that because a let got introduced into calc
by an earlier stage of the compiler. In fact any code involving a
let-introduced variable that isn't used in more than once place could be
simplified by substituting the variable for it's definition. For
example:

	let x = foo 10
	in bar x

will generate less instructions as:

	bar (foo 10)

But since it doesn't save a huge amount I deemed it not worth the effort
needed to detect unshared let introduced variables and remove them :-)

Thanks

Tom



On Thu, 2006-09-28 at 01:38 +0530, Kartik Vaddadi wrote:
> Hello,
> I compiled the following program using yhc:
> > main = print (calc 3)
> > calc x = munge x 6
> > munge x y  = x
> 
> The bytecode for calc starts with:
> 
>     NEED_HEAP_1
>     PUSH_CONST_0
>     PUSH_CONST_1
>     PUSH_ZAP_1
> 
> Couldn't this be simplified to:
>    NEED_HEAP_1
>    PUSH_CONST_1
>    PUSH_CONST_0
> 
> Thanks.
>