tests: Fix 'instruction does not dominate all its uses' error

The LLVM-IR of this test case was apperently incorrect.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@179672 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unneeded RegionSimplify pass.

We now support regions with multiple entries and multiple exits natively.
Regions are not needed to be simplified to single entry and single exit.

We need to XFAIL two test cases as this change increases the scop coverage
and uncoveres two failures in the independent blocks pass. The first failure
will be fixed in a subsequent commit, the second one is in the non-default
-polly-codegen-scev mode and still needs to be fixed.

Contributed-by: Star Tan <tanmx_star@yeah.net>

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@179673 91177308-0d34-0410-b5e6-96231b3b80d8
IndependentBlocks: We can only reconstruct PHI nodes that are within the ScoP

In the classical (non -polly-codegen-scev) mode, we assume that we can always
recreate PHI nodes during code generation. This is not true. We can only
reconstruct them from the polyhedral information, in case the entire loop of the
PHI node is part of the SCoP and consequently the PHI node was translated in
the polyhedral description.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@179674 91177308-0d34-0410-b5e6-96231b3b80d8