b3c54914ef
This is a small code size optimization that lets us avoid both shifting and comparing to a constant if we need the shifted value anyway. On most architectures the zero comparison is cheaper than a constant comparison (or free if the shift sets flags). Although this change appears to remove the optimization entirely, we continue to do this transform if there is one use because of the code below the removed code that transforms the shift into an and, followed by the PR10267 case in InstCombinerImpl::foldICmpAndConstConst that transforms the and into a ult/ugt. Added a test case to verify this explicitly. Per [1] reduces clang .text size by 0.09% and dynamic instruction count by 0.01%. [1] https://llvm-compile-time-tracker.com/compare.php?from=1f38d49ebe96417e368a567efa4d650b8a9ac30f&to=0873787a12b8f2eab019d8211ace4bccc1807343&stat=size-text Reviewers: nikic, dtcxzyw Reviewed By: dtcxzyw Pull Request: https://github.com/llvm/llvm-project/pull/168007