[llvm] [InstCombine] Implement folds of icmp of UCMP/SCMP call and a constant (PR #96118)

[Dhruv Chawla via llvm-commits]

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@@ -3926,6 +3926,92 @@ foldICmpUSubSatOrUAddSatWithConstant(ICmpInst::Predicate Pred,
       ConstantInt::get(Op1->getType(), EquivInt));
 }
 
+static Instruction *
+foldICmpOfCmpIntrinsicWithConstant(ICmpInst::Predicate Pred, IntrinsicInst *I,
+                                   const APInt &C,
+                                   InstCombiner::BuilderTy &Builder) {
+  Intrinsic::ID IID = I->getIntrinsicID();
+  Value *LHS = I->getOperand(0);
+  Value *RHS = I->getOperand(1);
+
+  switch (Pred) {
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dc03-work wrote:

This switch seems quite verbose, I feel that these cases can be merged because their bodies are basically identical and only the icmp opcodes differ:
- `ICMP_EQ` with `ICMP_NE`
- `ICMP_SGT` with `ICMP_SLE`
- `ICMP_SGE` with `ICMP_SLT`

https://github.com/llvm/llvm-project/pull/96118