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The included test case would return the incorrect results, because the expansion of an shift with a constant shift amount of 0 would generate undefined behavior. This is because ExpandShiftByConstant assumes that all shifts by constants with a value of 0 have already been optimized away. This doesn't happen for opaque constants and usually this isn't a problem, because opaque constants won't take this code path - they are not supposed to. In the case that the opaque constant has to be expanded by the legalizer, the legalizer would drop the opaque flag. In this case we hit the limitations of ExpandShiftByConstant and create incorrect code. This commit fixes the legalizer by not dropping the opaque flag when expanding opaque constants and adding an assertion to ExpandShiftByConstant to catch this not supported case in the future. This fixes <rdar://problem/16718472> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207304 91177308-0d34-0410-b5e6-96231b3b80d8
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