The following removes a special case to not merge a block with
only a non-local label. We have a restriction of non-local labels
to be the first statement (and label) in a block, but otherwise nothing,
if the last stmt of A is a non-local label then it will be still
the first statement of the combined A + B. In particular we'd
happily merge when there's a stmt after that label.
The check originates from the tree-ssa merge.
Bootstrapped and tested on x86_64-unknown-linux-gnu with all
languages.
* tree-cfg.cc (gimple_can_merge_blocks_p): Remove condition
rejecting the merge when A contains only a non-local label.