[clang] [CIR] Implement simple folding for unary operations (PR #174882)

[Henrich Lauko via cfe-commits]

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@@ -2479,6 +2479,39 @@ OpFoldResult cir::UnaryOp::fold(FoldAdaptor adaptor) {
       if (isBoolNot(previous))
         return previous.getInput();
 
+  // Fold constant unary operations.
+  if (auto srcConst = getInput().getDefiningOp<cir::ConstantOp>()) {
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xlauko wrote:

I believe standarc MLIR canonicalize pass uses dead code analysis for everythng once it is finished, so one does not need to do redundant clean up implementation.

https://github.com/llvm/llvm-project/pull/174882