[llvm-bugs] [Bug 35769] New: [ValueTracking] Can't make a non-negative value negative

via llvm-bugs llvm-bugs at lists.llvm.org
Thu Dec 28 09:03:16 PST 2017


https://bugs.llvm.org/show_bug.cgi?id=35769

            Bug ID: 35769
           Summary: [ValueTracking] Can't make a non-negative value
                    negative
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org

Reduced from: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=4729

opt -instcombine

define i32 @bar4(i32 %a) {
  %and = and i32 %a, 7
  %C2 = icmp sle i32 %and, -2147483648
  tail call void @llvm.assume(i1 %C2)
  store i1 %C2, i1* undef
  ret i32 -2147483648
}
declare void @llvm.assume(i1) nounwind

Craig - this looks like it came from D32651/rL301747

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