D86841 had an error where for statements with no conditional were
required to make progress. This is not true, this patch removes that
line, and adds regression tests.
Differential Revision: https://reviews.llvm.org/D91075
Since C++11, the C++ standard has a forward progress guarantee
[intro.progress], so all such functions must have the `mustprogress`
requirement. In addition, from C11 and onwards, loops without a non-zero
constant conditional or no conditional are also required to make
progress (C11 6.8.5p6). This patch implements these attribute deductions
so they can be used by the optimization passes.
Differential Revision: https://reviews.llvm.org/D86841
Atmn Patel