diff --git a/js/src/ion/MIR.cpp b/js/src/ion/MIR.cpp
index 9054d0e3f66..f8c9a65031f 100644
--- a/js/src/ion/MIR.cpp
+++ b/js/src/ion/MIR.cpp
@@ -229,11 +229,9 @@ void
 MDefinition::printOpcode(FILE *fp)
 {
     PrintOpcodeName(fp, op());
-    fprintf(fp, " ");
     for (size_t j = 0; j < numOperands(); j++) {
+        fprintf(fp, " ");
         getOperand(j)->printName(fp);
-        if (j != numOperands() - 1)
-            fprintf(fp, " ");
     }
 }
 
@@ -444,6 +442,21 @@ MConstant::printOpcode(FILE *fp)
     }
 }
 
+void
+MControlInstruction::printOpcode(FILE *fp)
+{
+    MDefinition::printOpcode(fp);
+    for (size_t j = 0; j < numSuccessors(); j++)
+        fprintf(fp, " block%d", getSuccessor(j)->id());
+}
+
+void
+MCompare::printOpcode(FILE *fp)
+{
+    MDefinition::printOpcode(fp);
+    fprintf(fp, " %s", js_CodeName[jsop()]);
+}
+
 void
 MConstantElements::printOpcode(FILE *fp)
 {
diff --git a/js/src/ion/MIR.h b/js/src/ion/MIR.h
index 1c6dcf02161..50481a7cc85 100644
--- a/js/src/ion/MIR.h
+++ b/js/src/ion/MIR.h
@@ -814,6 +814,8 @@ class MControlInstruction : public MInstruction
     bool isControlInstruction() const {
         return true;
     }
+
+    void printOpcode(FILE *fp);
 };
 
 class MTableSwitch
@@ -1907,6 +1909,8 @@ class MCompare
         return AliasSet::None();
     }
 
+    void printOpcode(FILE *fp);
+
   protected:
     bool congruentTo(MDefinition *const &ins) const {
         if (!MBinaryInstruction::congruentTo(ins))