[clang] [CIR] Upstream StackSave and StackRestoreOp (PR #136426)

[Amr Hesham via cfe-commits]

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@@ -1419,6 +1419,48 @@ def CallOp : CIR_CallOpBase<"call", [NoRegionArguments]> {
     }]>];
 }
 
+//===----------------------------------------------------------------------===//
+// StackSave & StackRestoreOp
+//===----------------------------------------------------------------------===//
+
+def StackSaveOp : CIR_Op<"stack_save"> {
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AmrDeveloper wrote:

Mmmmm, I think that llvm in general uses the same style without _ for example getElemenetPtr, but in CIR dialect we use different style, not sure if it make sense to rename stack_save to stacksave or not, what do you think @xlauko 🤔 

https://github.com/llvm/llvm-project/pull/136426