llvm dev - Aug 2008 - [LLVMdev] question about tail call elimination pass ..

Hi,

createTailCallEliminationPass() is able to turn recursive
functions into loops when the functions are written
in tail recursive form. However, I'm unable to get it
to convert mutually recursive functions to run without
a growing stack.

For example (in pseudo code)-

define fact(n,result)
    if n < 2
	then result
	else fact(n-1,result *n)

is converted into a loop correctly. However the following
mutually recursive pair -

define even(n)
	if n == 0
		then true
		else odd(n-1)

define odd(n)
	if n==0
		then false
		else even(n-1)

doesn't get to run in constant stack space.
Is that possible with llvm?

-Srikumar
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20080803/ee73eeb3/attachment.html>

On Aug 3, 2008, at 8:45 AM, kumar wrote:
> Hi,
>
> createTailCallEliminationPass() is able to turn recursive
> functions into loops when the functions are written
> in tail recursive form. However, I'm unable to get it
> to convert mutually recursive functions to run without
> a growing stack.
...
> doesn't get to run in constant stack space.
> Is that possible with llvm?
>
Sure, just run the function inliner pass first before the tail  
recursion elimination pass.

-Chris
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20080803/d42fb277/attachment.html>