[llvm] [InstCombine] Simplify compare abs(X) and X. (PR #76385)

[Yingwei Zheng via llvm-commits]

================
@@ -6860,6 +6860,54 @@ Instruction *InstCombinerImpl::foldICmpCommutative(ICmpInst::Predicate Pred,
       return foldICmpAddOpConst(X, *C, Pred);
   }
 
+  // abs(X) >=  X --> true
+  // abs(X) u<= X --> true
+  // abs(X) <   X --> false
+  // abs(X) u>  X --> false
+  // abs(X) u>= X --> IsIntMinPosion ? `X > -1`: `X u<= INTMIN`
+  // abs(X) <=  X --> IsIntMinPosion ? `X > -1`: `X u<= INTMIN`
+  // abs(X) ==  X --> IsIntMinPosion ? `X > -1`: `X u<= INTMIN`
+  // abs(X) u<  X --> IsIntMinPosion ? `X < 0` : `X >   INTMIN`
+  // abs(X) >   X --> IsIntMinPosion ? `X < 0` : `X >   INTMIN`
+  // abs(X) !=  X --> IsIntMinPosion ? `X < 0` : `X >   INTMIN`
+  {
+    Value *X;
+    Constant *C;
+    if ((match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X), m_Constant(C))) &&
+         match(Op1, m_Specific(X)))) {
----------------
dtcxzyw wrote:

```suggestion
    if (match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X), m_Constant(C))) &&
         match(Op1, m_Specific(X))) {
```

https://github.com/llvm/llvm-project/pull/76385