WIP: Implement ES6 Spread-calls

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index e56fc4a5702f3662125b6b911d8bd61d88418c0c..5b8745f583ba60e4291180f98290a103df9bf783 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -1884,14 +1884,17 @@ static void EmitSlowCase(Isolate* isolate,
                          MacroAssembler* masm,
                          StackArgumentsAccessor* args,
                          int argc,
-                         Label* non_function) {
+                         Label* non_function,
+                         bool is_spread = false) {
   // Check for function proxy.
   __ CmpInstanceType(rcx, JS_FUNCTION_PROXY_TYPE);
   __ j(not_equal, non_function);
   __ PopReturnAddressTo(rcx);
   __ Push(rdi);  // put proxy as additional argument under return address
   __ PushReturnAddressFrom(rcx);
-  __ Set(rax, argc + 1);
+  if (!is_spread) {
+    __ Set(rax, argc + 1);
+  }
   __ Set(rbx, 0);
   __ GetBuiltinEntry(rdx, Builtins::CALL_FUNCTION_PROXY);
   {
@@ -1904,7 +1907,9 @@ static void EmitSlowCase(Isolate* isolate,
   // of the original receiver from the call site).
   __ bind(non_function);
   __ movp(args->GetReceiverOperand(), rdi);
-  __ Set(rax, argc);
+  if (!is_spread) {
+    __ Set(rax, argc);
+  }
   __ Set(rbx, 0);
   __ GetBuiltinEntry(rdx, Builtins::CALL_NON_FUNCTION);
   Handle<Code> adaptor =
@@ -1915,29 +1920,40 @@ static void EmitSlowCase(Isolate* isolate,
 
 static void EmitWrapCase(MacroAssembler* masm,
                          StackArgumentsAccessor* args,
-                         Label* cont) {
+                         Label* cont, bool is_spread = false) {
   // Wrap the receiver and patch it back onto the stack.
   { FrameScope frame_scope(masm, StackFrame::INTERNAL);
+    // If is_spread is true, dynamic argument count is in $r8 temporarily
+    if (is_spread) __ Push(r8);
     __ Push(rdi);
     __ Push(rax);
     __ InvokeBuiltin(Builtins::TO_OBJECT, CALL_FUNCTION);
     __ Pop(rdi);
+    if (is_spread) __ Pop(r8);
+  }
+  if (is_spread) {
+    DCHECK(args->argument_count_reg().is(rax));
+    __ xchgp(rax, r8);
+    __ movp(args->GetReceiverOperand(), r8);
+  } else {
+    __ movp(args->GetReceiverOperand(), rax);
   }
-  __ movp(args->GetReceiverOperand(), rax);
   __ jmp(cont);
 }
 
 
 static void CallFunctionNoFeedback(MacroAssembler* masm,
                                    int argc, bool needs_checks,
-                                   bool call_as_method) {
+                                   bool call_as_method,
+                                   bool is_spread = false) {
   // rdi : the function to call
+  // rcx : the dynamic argument count (if is_spread is true)
 
   // wrap_and_call can only be true if we are compiling a monomorphic method.
   Isolate* isolate = masm->isolate();
   Label slow, non_function, wrap, cont;
-  StackArgumentsAccessor args(rsp, argc);
-
+  StackArgumentsAccessor args = is_spread ?
+      StackArgumentsAccessor(rsp, rax) : StackArgumentsAccessor(rsp, argc);
   if (needs_checks) {
     // Check that the function really is a JavaScript function.
     __ JumpIfSmi(rdi, &non_function);
@@ -1948,14 +1964,19 @@ static void CallFunctionNoFeedback(MacroAssembler* masm,
   }
 
   // Fast-case: Just invoke the function.
-  ParameterCount actual(argc);
+  ParameterCount actual = is_spread ?
+      ParameterCount(rax) : ParameterCount(argc);
 
   if (call_as_method) {
+    // If is_spread is true, preserve dynamic argument count in r8
+    if (is_spread) __ xchgp(r8, rax);
+
     if (needs_checks) {
       EmitContinueIfStrictOrNative(masm, &cont);
     }
 
-    // Load the receiver from the stack.
+    // Load the receiver from the stack. If is_spread is true, args is now
+    // broken.
     __ movp(rax, args.GetReceiverOperand());
 
     if (needs_checks) {
@@ -1975,18 +1996,19 @@ static void CallFunctionNoFeedback(MacroAssembler* masm,
   if (needs_checks) {
     // Slow-case: Non-function called.
     __ bind(&slow);
-    EmitSlowCase(isolate, masm, &args, argc, &non_function);
+    EmitSlowCase(isolate, masm, &args, argc, &non_function, is_spread);
   }
 
   if (call_as_method) {
     __ bind(&wrap);
-    EmitWrapCase(masm, &args, &cont);
+    EmitWrapCase(masm, &args, &cont, is_spread);
   }
 }
 
 
 void CallFunctionStub::Generate(MacroAssembler* masm) {
-  CallFunctionNoFeedback(masm, argc(), NeedsChecks(), CallAsMethod());
+  CallFunctionNoFeedback(masm, argc(), NeedsChecks(), CallAsMethod(),
+                         is_spread());
 }
 
 
@@ -2113,6 +2135,7 @@ void CallIC_ArrayStub::Generate(MacroAssembler* masm) {
 
 
 void CallICStub::Generate(MacroAssembler* masm) {
+  // rax - argument count (only if call is a spread call)
   // rdi - function
   // rdx - slot id
   // rbx - vector
@@ -2125,8 +2148,10 @@ void CallICStub::Generate(MacroAssembler* masm) {
   Label slow, non_function, wrap, cont;
   Label have_js_function;
   int argc = arg_count();
-  StackArgumentsAccessor args(rsp, argc);
-  ParameterCount actual(argc);
+  StackArgumentsAccessor args = is_spread() ?
+      StackArgumentsAccessor(rsp, rax) : StackArgumentsAccessor(rsp, argc);
+  ParameterCount actual = is_spread() ?
+      ParameterCount(rax) : ParameterCount(argc);
 
   // The checks. First, does rdi match the recorded monomorphic target?
   __ SmiToInteger32(rdx, rdx);