Cleanup: Make CheckClassId instruction more general so it

runtime/vm/simulator_dbc.cc

Index: runtime/vm/simulator_dbc.cc
diff --git a/runtime/vm/simulator_dbc.cc b/runtime/vm/simulator_dbc.cc
index a85f26d7cf5f3f0078645e224c7cf2c80d91cec7..8c7bfcc2a947edb5c11502ffaddc93a2121f2422 100644
--- a/runtime/vm/simulator_dbc.cc
+++ b/runtime/vm/simulator_dbc.cc
@@ -3254,6 +3254,17 @@ RawObject* Simulator::Call(const Code& code,
   }
 
   {
+    BYTECODE(CheckClassIdRange, A_B_C);
+    const intptr_t actual_cid =
+        reinterpret_cast<intptr_t>(FP[rA]) >> kSmiTagSize;
+    const uintptr_t cid_start = rB;
+    const uintptr_t cid_end = rC;
+    // Unsigned comparison.
+    pc += (actual_cid - cid_start <= cid_end + 1u - cid_start) ? 1 : 0;

[kustermann, 2017/05/18 09:59:45]

If

  [cid_start, cid_end] = [0, 1]
  actual_cid = 2

This translates to

  2 - 0 <= 1 + 1 - 0
  2     <= 2

despite actual_cid not in [cid_start, cid_end]!

[erikcorry, 2017/05/18 14:25:30]

Oops, fixed.

+    DISPATCH();
+  }
+
+  {
     BYTECODE(CheckBitTest, A_D);
     const intptr_t raw_value = reinterpret_cast<intptr_t>(FP[rA]);
     const bool is_smi = ((raw_value & kSmiTagMask) == kSmiTag);