[llvm] [KnownBits] Fix minimum denominator bounds for sdiv (PR #227264)

[Matt Arsenault via llvm-commits]

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@@ -1255,7 +1255,11 @@ KnownBits KnownBits::sdiv(const KnownBits &LHS, const KnownBits &RHS,
     if (Exact || (-LHS.getSignedMaxValue()).uge(RHS.getSignedMaxValue())) {
       APInt Denom = RHS.getSignedMinValue();
       APInt Num = LHS.getSignedMinValue();
-      Res = Denom.isZero() ? Num : Num.sdiv(Denom);
+      // fix to set the lowest unknown bit to get the minimum non-zero
+      // denominator
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arsenm wrote:

Comment can be improved and needs capitalization. This isn't really a "fix", it's an improvement?

https://github.com/llvm/llvm-project/pull/227264