As mentioned in #68882 and https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699 Gep arithmetic isn't consistent with different types. GVNSink didn't realize this and sank all geps as long as their operands can be wired via PHIs in a post-dominator. Fixes: #85333 Reapply: #88440 after fixing the non-determinism issues in #90995