forked from OSchip/llvm-project
29f189f90d
Currently, the InstCombineCompare is combining two add operations into a single add operation which always has a nsw flag, without checking the conditions to see if this flag should be present according to the original two add operations or not. This patch will change the InstCombineCompare to emit the nsw or nuw only when these flags are allowed to be generated according to the original add operations and remove the possibility of applying wrong optimization with passes that will perform on the IR later in the pipeline. To confirm that the current results are buggy and the results after proposed patch are the correct IR the following examples from Alive2 are attached; the same results can be seen in the case of nuw flag and nsw is just used as an example. The following link shows that the generated IR with current LLVM is a buggy IR when none of the original add operations have nsw flag. https://alive2.llvm.org/ce/z/WGaDrm The following link proves that the generated IR after the patch in the former case is the correct IR. https://alive2.llvm.org/ce/z/wQ7G_e Differential Revision: https://reviews.llvm.org/D100095 |
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