This is an example on how I'd like to see cleanup for SLP happening
in the vectorizable_* and related functions. While this example,
vectorizable_conversion, is quite straight-forward it helps to
isolate errors. I've done this in 3 steps:
1) fold trivially true/false conditions based on the slp_node argument
without code block removal/reindent, etc.
2) do trivial dead code elimination
3) cleanup simple things - it's expected that the 'ncopies' variable
vanishes (a vec_num one might remain), the function should no
longer access STMT_VINFO_VECTYPE (but SLP_TREE_VECTYPE), the
callers then no longer need to swap those in.
Before committing the steps should be squashed into a single commit,
I've put the actual changelog into [3/3].
Richard.
