[LLVMdev] Which pass converts call printf to puts?

[Christoph Erhardt]

Hi Thomson,

> Could you give an example of the old instruction cannot be removed
> safely? Since the new instruction would produce the same context/result
> of the old one, I suppose it is safe to remove the old one when the new
> instruction is ready (inserted after the old one). Anything I missed here?
yes, you're missing that LLVM programs are in SSA form: A new
instruction always produces a new result.

Imagine a graph in which every instruction is represented as a node and
every use-relationship is represented as a directed edge. Now if you
want to replace a node with another node, you have to make sure to
properly reconnect all incoming and outgoing edges of the old node,
otherwise they'll be dangling.

Best regards,
Christoph