shrink-wrap: Don't put on incoming EDGE_CROSSING [PR98289]

shrink-wrap: Don't put on incoming EDGE_CROSSING [PR98289]

As mentioned in the PR, shrink-wrapping disqualifies for prologue
placement basic blocks that have EDGE_CROSSING incoming edge.
I don't see why that is necessary, those edges seem to be redirected
just fine, both on x86_64 and powerpc64.  In the former case, they
are usually conditional jumps that patch_jump_insn can handle just fine,
after all, they were previously crossing and will be crossing after
the redirection too, just to a different label.  And in the powerpc64
case, it is a simple_jump instead that again seems to be handled by
patch_jump_insn just fine.
Sure, redirecting an edge that was previously not crossing to be crossing or
vice versa can fail, but that is not what shrink-wrapping needs.
Also tested in GCC 8 with this patch and don't see ICEs there either
(though, of course, I'm not suggesting we should backport this to release
branches).
The old ICEs could have been fixed by PR87475 fix or some other one
years ago.

2020-12-17  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/98289
	* shrink-wrap.c (can_get_prologue): Don't punt on EDGE_CROSSING
	incoming edges.

	* gcc.target/i386/pr98289.c: New test.
	* gcc.dg/torture/pr98289.c: New test.