[Bug 84232] PHINode containing itself causes segfault in LLVM when compiling Blender OpenCL kernel with R600 backend

Comment # 2 on bug 84232 from Vitaliy Filippov

Created attachment 107527 [details]
Attempt to reduce testcase using bugpoint

Tried to reduce the case using bugpoint:

PATH=/usr/lib/llvm-3.5/bin/:$PATH bugpoint-3.5 kernel.ll --llc-safe --tool-args
-- -march=r600 -mcpu=oland

The result leads to other crash, maybe it's also a bug, but it's definitely
another bug:

llc-3.5 -march=r600 -mcpu=oland bugpoint-reduced-simplified.ll

Which leads to a segfault on a non-assert build and to the following message on
a release+asserts build:

Unhandled loop condition!
UNREACHABLE executed at

This is probably related to bugpoint replacing the branch conditions with
constants, which makes conditional branches effectively unconditional :) and
SIAnnotateControlFlow::handleLoopCondition also doesn't handle this case.

Looks like an easy to fix problem?