[llvm-bugs] [Bug 31809] New: Assertion failed: ((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"), function computeKnownBits, file lib/Analysis/ValueTracking.cpp, line 1606.

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31809

            Bug ID: 31809
           Summary: Assertion failed: ((KnownZero & KnownOne) == 0 &&
                    "Bits known to be one AND zero?"), function
                    computeKnownBits, file lib/Analysis/ValueTracking.cpp,
                    line 1606.
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: dimitry at andric.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

>From https://bugs.freebsd.org/216614, building recent versions of emacs with
recent clang can fail with an assertion:

Assertion failed: ((KnownZero & KnownOne) == 0 && "Bits known to be one AND
zero?"), function computeKnownBits, file lib/Analysis/ValueTracking.cpp, line
1606.

Reduced test case, reproduces with trunk r293557:

/* clang -cc1 -triple x86_64 -S -O2 testcase.c */
enum { x0, x1 } x2(long x3, x4) { return __builtin_assume_aligned(x3 - x4, 8);
}
x5(void *x3) { return x3; }
union x6 {
  int x7
} x8() {
  long x9 = x5(&(union x6){});
  x2(x9, x1);
}

This started to appear somewhere between r282311 and r289043, no narrower
window yet.

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