Create a stub of performance_counter (#41)

The stub will be replaced with a proper implementation once its semantics gets clarified.

src/IC/Canister/Imp.hs

@@ -227,9 +227,10 @@ systemAPI esref =
 
   , toImport "ic0" "msg_method_name_size" msg_method_name_size
   , toImport "ic0" "msg_method_name_copy" msg_method_name_copy
-  , toImport "ic0" "accept_message" accept_message
 
+  , toImport "ic0" "accept_message" accept_message
   , toImport "ic0" "time" get_time
+  , toImport "ic0" "performance_counter" performance_counter
 
   , toImport "ic0" "debug_print" debug_print
   , toImport "ic0" "trap" explicit_trap
@@ -521,6 +522,10 @@ systemAPI esref =
         Timestamp ns <- gets (env_time . env)
         return (fromIntegral ns)
 
+    -- TODO: implement once semantics of performance_counter is known.
+    performance_counter :: () -> HostM s Word64
+    performance_counter () = return 0
+
     debug_print :: (Int32, Int32) -> HostM s ()
     debug_print (src, size) = do
       -- TODO: This should be a non-trapping copy

src/IC/Test/Spec.hs

@@ -669,6 +669,7 @@ icTests = withAgentConfig $ testGroup "Interface Spec acceptance tests"
     , t "msg_method_name"              "F"             $ ignore methodName
     , t "accept_message"               never             acceptMessage -- due to double accept
     , t "time"                         star            $ ignore getTime
+    , t "performance_counter"          star            $ ignore performanceCounter
     , t "debug_print"                  star            $ debugPrint "hello"
     , t "trap"                         never           $ trap "this better traps"
     ]

src/IC/Test/Universal.hs

@@ -225,6 +225,9 @@ stable64Write = op 48
 onHeartbeat :: Exp 'B -> Prog
 onHeartbeat = op 49
 
+performanceCounter :: Exp 'I64
+performanceCounter = op 50
+
 -- Some convenience combinators
 
 -- This allows us to write byte expressions as plain string literals

universal-canister/src/api.rs

@@ -57,6 +57,7 @@ mod ic0 {
         pub fn data_certificate_copy(dst: u32, offset: u32, size: u32) -> ();
 
         pub fn time() -> u64;
+        pub fn performance_counter() -> u64;
     }
 }
 
@@ -258,6 +259,12 @@ pub fn accept_message() {
     unsafe { ic0::accept_message() }
 }
 
+pub fn performance_counter() -> u64 {
+    unsafe {
+        ic0::performance_counter()
+    }
+}
+
 pub fn method_name() -> Vec<u8> {
     let len: u32 = unsafe { ic0::msg_method_name_size() };
     let mut bytes = vec![0; len as usize];

universal-canister/src/main.rs

@@ -284,6 +284,8 @@ fn eval(ops: Ops) {
             // canister heartbeat script
             49 => set_heartbeat(stack.pop_blob()),
 
+            50 => stack.push_int64(api::performance_counter()),
+
             _ => api::trap_with(&format!("unknown op {}", op)),
         }
     }