[llvm] [InstSimplify] Simplify the select with integer comparison relationship (PR #66668)

[Yingwei Zheng via llvm-commits]

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@@ -8285,6 +8285,15 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
   if (areMatchingOperands(L0, L1, R0, R1, AreSwappedOps))
     return isImpliedCondMatchingOperands(LPred, RPred, AreSwappedOps);
 
+  if (RPred == ICmpInst::ICMP_SLT) {
+    Value *X;
+    Value *Y;
+    // x -nsw y is non-negative when x >= y or negative when x < y
+    if (match(R0, m_NSWSub(m_Value(X), m_Value(Y))) && match(R1, m_AllOnes()) &&
+        areMatchingOperands(L0, L1, X, Y, AreSwappedOps))
+      return isImpliedCondMatchingOperands(LPred, RPred, AreSwappedOps);
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dtcxzyw wrote:

It is incorrect that `X <s Y` implies `X -nsw Y <s -1`.


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