[clang] [CIR] Add side effect attribute to call operations (PR #144201)

[Bruno Cardoso Lopes via cfe-commits]

================
@@ -1858,6 +1858,40 @@ def FuncOp : CIR_Op<"func", [
 // CallOp
 //===----------------------------------------------------------------------===//
 
+def SE_All : I32EnumAttrCase<"All", 1, "all">;
+def SE_Pure : I32EnumAttrCase<"Pure", 2, "pure">;
+def SE_Const : I32EnumAttrCase<"Const", 3, "const">;
+
+def SideEffect
+    : I32EnumAttr<
+          "SideEffect",
+          "allowed side effects of a function", [SE_All, SE_Pure, SE_Const]> {
+  let description = [{
+    The side effect attribute specifies the possible side effects of the callee
+    of a call operation. This is an enumeration attribute and all possible
+    enumerators are:
+
+    - all: The callee can have any side effects. This is the default if no side
+      effects are explicitly listed.
+    - pure: The callee may read data from memory, but it cannot write data to
----------------
bcardosolopes wrote:

Oh I see, clarity is indeed key, didn't think from that perspective.

> Do we represent side-effects on LLVM intrinsic calls?

If you mean whether `LLVMIntrinsicCallOp` does it, the answer is no but we should (likewise for the whole family of CIR operations that mostly cover intrinsics). We'll definitely need them for things like `llvm/test/Verifier/fp-intrinsics-pass.ll`, etc.

This is a good reminder so we pay close attention for when PRs for all those arrive, so we can make sure those operations will include a way to handle such attributes.

https://github.com/llvm/llvm-project/pull/144201