[X86] Don't model UD2/UD2B as a terminator
A UD2 might make its way into the program via a call to @llvm.trap.
Obviously, calls are not terminators. However, we modeled the X86
instruction, UD2, as a terminator. Later on, this confuses the epilogue
insertion machinery which results in the epilogue getting inserted
before the UD2. For some platforms, like x64, the result is a
violation of the ABI.
Instead, model UD2/UD2B as a side effecting instruction which may
observe memory.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278144
91177308-0d34-0410-b5e6-
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