VM: Fix a couple of issues in the AOT optimizer, add fast path smi multiply.

runtime/vm/intermediate_language_arm.cc

Index: runtime/vm/intermediate_language_arm.cc
diff --git a/runtime/vm/intermediate_language_arm.cc b/runtime/vm/intermediate_language_arm.cc
index 6b180bd47e97a2cca9ed5e5717431abe8ee1a58c..a2c6b9797eea130a8d7f2cd0bd3e63cc5670a48b 100644
--- a/runtime/vm/intermediate_language_arm.cc
+++ b/runtime/vm/intermediate_language_arm.cc
@@ -3105,6 +3105,13 @@ void CheckedSmiOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
       __ subs(result, left, Operand(right));
       __ b(slow_path->entry_label(), VS);
       break;
+    case Token::kMUL:
+      __ SmiUntag(IP, left);
+      __ smull(result, IP, IP, right);
+      // IP: result bits 32..63.
+      __ cmp(IP, Operand(result, ASR, 31));
+      __ b(slow_path->entry_label(), NE);
+      break;
     case Token::kBIT_OR:
       // Operation part of combined smi check.
       break;