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616011418e
Fixes PR16130 - clang produces incorrect code with loop/expression at -O2. This is a 2+ year old bug that's now holding up the release. It's a case where we knowingly made aggressive assumptions about undefined behavior. These assumptions are wrong when SCEV is computing a subexpression that does not directly control the branch. With this fix, we avoid making assumptions in those cases but still optimize the common case. SCEV's trip count computation for exits controlled by 'or' expressions is now analagous to the trip count computation for loops with multiple exits. I had already fixed the multiple exit case to be conservative. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182989 91177308-0d34-0410-b5e6-96231b3b80d8