[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:

> nit: Also any reason not to mirror llvm names, i.e. to have cir.stacksave and cir.stackrestore?

I found that we use the same name pattern in general, for example `get_global`, `ptr_stride ` ...etc, but I think in this case we can mirror the llvm names, I will update it

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