This reverts commit 354fa0b48008eca701a110badd6974bf449df257. Returning as is. The patch was reverted due to a miscompile, but this patch is not causing it. This patch made it possible to infer some nuw flags in code guarded by `false` condition, and then someone else to managed to propagate the flag from dead code outside. Returning the patch to be able to reproduce the issue.