[llvm] Simplify `(a % b) lt/ge (b-1)` into `(a % b) eq/ne (b-1)` (PR #72504)

[Yingwei Zheng via llvm-commits]

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@@ -6837,6 +6837,25 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
     Changed = true;
   }
 
+  {
+    Value *X, *Y;
+    const APInt *C;
+    ICmpInst::Predicate Pred = I.getPredicate();
+    if ((Pred == ICmpInst::ICMP_SGE || Pred == ICmpInst::ICMP_SLT) &&
+        match(Op0, m_OneUse(m_SRem(m_Value(X), m_Value(Y)))) &&
+        ((match(Op1, m_OneUse(m_c_Add(m_Deferred(Y), m_AllOnes()))) &&
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dtcxzyw wrote:

We can simplify `icmp sle/sgt (srem X, Y), (Y + 1)` into `icmp eq/ne (srem X, Y), (Y + 1)` if we know `Y` is negative.


https://github.com/llvm/llvm-project/pull/72504