Make context register implicit for CallInterfaceDescriptors

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index 6b104ce2438a216158d0fdc1b9cd2eee0dc905d7..6a123d6acece7d9eb902b38bd81e092cc31592ce 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -1861,8 +1861,12 @@ class LCallWithDescriptor final : public LTemplateResultInstruction<1> {
  public:
   LCallWithDescriptor(CallInterfaceDescriptor descriptor,
                       const ZoneList<LOperand*>& operands, Zone* zone)
-      : inputs_(descriptor.GetRegisterParameterCount() + 1, zone) {
-    DCHECK(descriptor.GetRegisterParameterCount() + 1 == operands.length());
+      : inputs_(descriptor.GetRegisterParameterCount() +
+                    kImplicitRegisterParameterCount,
+                zone) {
+    DCHECK(descriptor.GetRegisterParameterCount() +
+               kImplicitRegisterParameterCount ==
+           operands.length());
     inputs_.AddAll(operands, zone);
   }
 
@@ -1870,6 +1874,10 @@ class LCallWithDescriptor final : public LTemplateResultInstruction<1> {
 
   DECLARE_HYDROGEN_ACCESSOR(CallWithDescriptor)
 
+  // The target and context are passed as implicit parameters that are not
+  // explicitly listed in the descriptor.
+  static const int kImplicitRegisterParameterCount = 2;
+
  private:
   DECLARE_CONCRETE_INSTRUCTION(CallWithDescriptor, "call-with-descriptor")