[llvm] [ValueTracking] Infer relationship for the select with ICmp (PR #66668)

[via llvm-commits]

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@@ -8883,6 +8883,26 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
   if (L0 == R0 && L1 == R1)
     return isImpliedCondMatchingOperands(LPred, RPred);
 
+  // It only really makes sense in the context of signed comparison for "X - Y
+  // must be positive if X >= Y and no overflow".
+  // Take SGT as an example:  L0:x > L1:y and C >= 0
+  //                      ==> R0:(x -nsw y) < R1:(-C) is false
+  if ((LPred == ICmpInst::ICMP_SGT || LPred == ICmpInst::ICMP_SGE) &&
+      match(R0, m_NSWSub(m_Specific(L0), m_Specific(L1)))) {
+    if (match(R1, m_NonPositive()) &&
+        isImpliedCondMatchingOperands(LPred, RPred) == false)
+      return false;
+  }
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goldsteinn wrote:

I made a mistake think this is okay.

https://github.com/llvm/llvm-project/pull/66668