Add back test

Author: Centri3

tests/codegen/is_compile_time_known.rs

@@ -0,0 +1,47 @@
+// compile-flags: --crate-type=lib
+#![feature(core_intrinsics)]
+
+use std::intrinsics::is_compile_time_known;
+
+pub struct A(u32);
+pub enum B {
+    Ye(u32),
+}
+
+#[inline]
+pub fn tuple_struct(a: A) -> i32 {
+    if unsafe { is_compile_time_known(a) } { 1 } else { 0 }
+}
+
+// CHECK-LABEL: @tuple_struct_true(
+#[no_mangle]
+pub fn tuple_struct_true() -> i32 {
+    // CHECK: ret i32 1
+    tuple_struct(A(1))
+}
+
+// CHECK-LABEL: @tuple_struct_false(
+#[no_mangle]
+pub fn tuple_struct_false(a: A) -> i32 {
+    // CHECK: ret i32 0
+    tuple_struct(a)
+}
+
+#[inline]
+pub fn r#enum(b: B) -> i32 {
+    if unsafe { is_compile_time_known(b) } { 3 } else { 2 }
+}
+
+// CHECK-LABEL: @enum_true(
+#[no_mangle]
+pub fn enum_true() -> i32 {
+    // CHECK: ret i32 3
+    r#enum(B::Ye(2))
+}
+
+// CHECK-LABEL: @enum_false(
+#[no_mangle]
+pub fn enum_false(b: B) -> i32 {
+    // CHECK: ret i32 2
+    r#enum(b)
+}