[llvm] [ValueTracking] Fix bug of using wrong condition for deducing KnownBits (PR #124481)

[via llvm-commits]

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@@ -1705,9 +1711,10 @@ static void computeKnownBitsFromOperator(const Operator *I,
                     m_Br(m_c_ICmp(Pred, m_Specific(IncValue), m_APInt(RHSC)),
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goldsteinn wrote:

I don't think so. Take the test case. If the branch in `%B1` used a `%cmp` on `%sub` that would be patently incorrect to use when analyzing `%sub` in `%B0`

https://github.com/llvm/llvm-project/pull/124481