Make context register implicit for CallInterfaceDescriptors

src/arm/lithium-arm.h

Index: src/arm/lithium-arm.h
diff --git a/src/arm/lithium-arm.h b/src/arm/lithium-arm.h
index 4c5f3a335db8a038a5725def38f0f7b78d6bc52e..d61c3d4c0dd265c776388fdcdaa47b1ceeaf1e4b 100644
--- a/src/arm/lithium-arm.h
+++ b/src/arm/lithium-arm.h
@@ -1847,8 +1847,12 @@ class LCallWithDescriptor final : public LTemplateResultInstruction<1> {
   LCallWithDescriptor(CallInterfaceDescriptor descriptor,
                       const ZoneList<LOperand*>& operands, Zone* zone)
       : descriptor_(descriptor),
-        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);
   }
 
@@ -1858,6 +1862,10 @@ 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")