[llvm-bugs] [Bug 32949] New: [InstSimplify] Miscompilation of sdiv + udiv

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=32949

            Bug ID: 32949
           Summary: [InstSimplify] Miscompilation of sdiv + udiv
           Product: libraries
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Keywords: miscompilation
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: nunoplopes at sapo.pt
                CC: david.majnemer at gmail.com, llvm-bugs at lists.llvm.org,
                    regehr at cs.utah.edu, spatel+llvm at rotateright.com

InstSimplify miscompiles the following:

define i2 @func68396950(i2) {
  %2 = sdiv exact i2 1, %0
  %3 = sdiv exact i2 -1, %0
  %4 = udiv i2 %2, %3
  ret i2 %4
}

$ opt -S a.ll -instsimplify
define i2 @func68396950(i2) {
  ret i2 0
}


Alive says:
ERROR: Mismatch in values of i2 ret_

Example:
%0 i2 = 0x3 (3, -1)
%2 i2 = 0x3 (3, -1)
%3 i2 = 0x1 (1)
%4 i2 = 0x3 (3, -1)
Source value: 0x3 (3, -1)
Target value: 0x0 (0)

http://rise4fun.com/Alive/5mO

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