[clang] [CIR] Attempt to fold casts and unary ops during codegen (PR #175675)

[Henrich Lauko via cfe-commits]

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@@ -66,6 +66,17 @@ struct RemoveRedundantBranches : public OpRewritePattern<BrOp> {
   }
 };
 
+struct RemoveUnusedConstants : public OpRewritePattern<ConstantOp> {
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xlauko wrote:

Btw as I did explaration of application of the canonicalization/folding thorughout clangir, as discussed yesterday, I believe it is worth just enabling folding in CIRCanonicalize pass on all CIR operations, so one does not need to add them explicitly all the time. I will look into this after your change, I have some draft of this change but it was changing too many test check, though it might take some time to get trough it.

https://github.com/llvm/llvm-project/pull/175675