[llvm-bugs] [Bug 43251] New: [InstCombine] Failure to simplify usub.with.overflow+null check of non-null base pointer

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43251

            Bug ID: 43251
           Summary: [InstCombine] Failure to simplify
                    usub.with.overflow+null check of non-null base pointer
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: llvm-bugs at lists.llvm.org

Again comes up in https://reviews.llvm.org/D67122
for 

char* test(char& base, unsigned long offset) {
  return &base - offset;
}

We produce 

https://godbolt.org/z/luGEju

and fail to simplify further, but we can:

https://rise4fun.com/Alive/Ppo

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