[clang] feat: included support for is_constant builtin (PR #166832)

[Henrich Lauko via cfe-commits]

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@@ -3043,6 +3043,44 @@ def CIR_ArrayDtor : CIR_ArrayInitDestroy<"array.dtor"> {
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// IsConstantOp
+//===----------------------------------------------------------------------===//
+
+def CIR_IsConstantOp : CIR_Op<"is_constant", [Pure]> {
+  let summary = "Check if a value is a compile-time constant";
+  let description = [{
+    The `cir.is_constant` operation checks whether its input value is a
+    compile-time constant. This operation models the `__builtin_constant_p`
+    builtin function.
+
+    The operation takes a single operand of any CIR type and returns a signed
+    32-bit integer. The result is 1 if the operand is a compile-time constant,
+    and 0 otherwise.
----------------
xlauko wrote:

This is not true, the expected result is bool

https://github.com/llvm/llvm-project/pull/166832