[llvm] [SCCP] Simplify [us]cmp(X, Y) into X - Y (PR #144717)

[Nikita Popov via llvm-commits]

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@@ -245,11 +245,46 @@ static Value *simplifyInstruction(SCCPSolver &Solver,
   const APInt *RHSC;
   // Remove masking operations.
   if (match(&Inst, m_And(m_Value(X), m_LowBitMask(RHSC)))) {
-    ConstantRange LRange = GetRange(Inst.getOperand(0));
+    ConstantRange LRange = GetRange(X);
     if (LRange.getUnsignedMax().ule(*RHSC))
       return X;
   }
 
+  if (auto *II = dyn_cast<IntrinsicInst>(&Inst)) {
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nikic wrote:

Could do this to skip the IID checks:
```suggestion
  if (auto *Cmp = dyn_cast<CmpIntrinsic>(&Inst)) {
```

https://github.com/llvm/llvm-project/pull/144717