[stubs] Simplify the non-function case of CallConstructStub.

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index ced550b59ad6fb2c718a96257781758e084efdb5..78afc46c6e1ea8e1dbdba592e05655a48dd58276 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -2528,22 +2528,35 @@ void CallConstructStub::Generate(MacroAssembler* masm) {
   // r0: number of arguments
   // r1: called object
   // r5: object type
-  Label do_call;
   __ bind(&slow);
-  __ cmp(r5, Operand(JS_FUNCTION_PROXY_TYPE));
-  __ b(ne, &non_function_call);
-  __ GetBuiltinFunction(
-      r1, Context::CALL_FUNCTION_PROXY_AS_CONSTRUCTOR_BUILTIN_INDEX);
-  __ jmp(&do_call);
-
-  __ bind(&non_function_call);
-  __ GetBuiltinFunction(
-      r1, Context::CALL_NON_FUNCTION_AS_CONSTRUCTOR_BUILTIN_INDEX);
-  __ bind(&do_call);
-  // Set expected number of arguments to zero (not changing r0).
-  __ mov(r2, Operand::Zero());
-  __ Jump(masm->isolate()->builtins()->ArgumentsAdaptorTrampoline(),
-          RelocInfo::CODE_TARGET);
+  {
+    // Overwrite the original receiver with the (original) target (not necessary
+    // in case of rdi being smi, when we jump directly to non_function_call
+    // below).
+    __ str(r1, MemOperand(sp, r0, LSL, kPointerSizeLog2));

[Michael Starzinger, 2015/09/11 09:17:37]

This is confusing. Why do we suddenly need to patch the receiver to point to the
target function? If this is really needed, can we clarify the comment so that
people understand why this patching happens?

[Benedikt Meurer, 2015/09/11 09:20:28]

You're right, receiver stays the same.

+
+    __ cmp(r5, Operand(JS_FUNCTION_PROXY_TYPE));
+    __ b(ne, &non_function_call);
+    // TODO(neis): This doesn't match the ES6 spec for [[Construct]] on proxies.
+    __ ldr(r1, FieldMemOperand(r1, JSFunctionProxy::kConstructTrapOffset));
+    __ Jump(isolate()->builtins()->Call(), RelocInfo::CODE_TARGET);
+
+    __ bind(&non_function_call);
+    {
+      // Determine the delegate for the target (if any).
+      FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
+      __ SmiTag(r0);
+      __ Push(r0, r1);
+      __ CallRuntime(Runtime::kGetConstructorDelegate, 1);
+      __ mov(r1, r0);
+      __ Pop(r0);
+      __ SmiUntag(r0);
+    }
+    // The delegate is always a regular function.
+    __ AssertFunction(r1);
+    __ Jump(masm->isolate()->builtins()->CallFunction(),
+            RelocInfo::CODE_TARGET);
+  }
 }