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

[Henrich Lauko via cfe-commits]

================
@@ -4052,6 +4093,44 @@ def CIR_ExpectOp : CIR_Op<"expect", [
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// 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.
+
+    If the value can be determined to be constant at compile time, this
+    operation may be folded to a constant value. Otherwise, it will be lowered
+    to the `llvm.is.constant` intrinsic.
+
+    Example:
+
+    ```mlir
+    %0 = cir.is_constant %expr : i32 -> !s32i
+    %1 = cir.is_constant %ptr : !cir.ptr<i32> -> !s32i
+    ```
+  }];
+
+  let arguments = (ins CIR_AnyType:$value);
+  let results = (outs CIR_SInt32:$result);
+
+  let assemblyFormat = [{
+    $value `:` type($value) `->` type($result) attr-dict
----------------
xlauko wrote:

@andykaylor pretty much yes. I am traying us to converge on style `: argument types -> return types` respectivelly `: type` if the operation can be determined by a single type. Bit of style guide is in: https://llvm.github.io/clangir/Dialect/cir-style-guide.html



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