[llvm] [InstCombine] Simplify select using KnownBits of condition (PR #95923)

[Yingwei Zheng via llvm-commits]

================
@@ -4018,5 +4045,32 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
   if (CondVal->getType() == SI.getType() && isKnownInversion(FalseVal, TrueVal))
     return BinaryOperator::CreateXor(CondVal, FalseVal);
 
+  if (SelType->isIntOrIntVectorTy()) {
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dtcxzyw wrote:

```suggestion
  if (SelType->isIntOrIntVectorTy() && (!isa<Constant>(TrueVal) || !isa<Constant>(FalseVal))) {
```
We can early exit if both of select arms are constants.


https://github.com/llvm/llvm-project/pull/95923