WIP: Implement ES6 Spread-calls

src/x64/full-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 2894 matching lines @@
   // - target function
   // - this (receiver)
   EmitCall(expr, CallICState::METHOD);
 }
 
 
 void FullCodeGenerator::EmitCall(Call* expr, CallICState::CallType call_type) {
   // Load the arguments.
   ZoneList<Expression*>* args = expr->arguments();
   int arg_count = args->length();
+  if (expr->HasSpreadArguments()) {
+    __ movp(rax, Immediate(arg_count));
+  }
+
   { PreservePositionScope scope(masm()->positions_recorder());
     for (int i = 0; i < arg_count; i++) {
-      VisitForStackValue(args->at(i));
+      Expression* e = args->at(i);
+      if (e->IsSpreadOperation()) {
+        DoSpreadArgument(e->AsSpreadOperation(), rax);
+      } else {
+        VisitForStackValue(args->at(i));
+      }
     }
   }
 
   // Record source position of the IC call.
   SetSourcePosition(expr->position());
-  Handle<Code> ic = CodeFactory::CallIC(isolate(), arg_count, call_type).code();
-  __ Move(rdx, SmiFromSlot(expr->CallFeedbackICSlot()));
-  __ movp(rdi, Operand(rsp, (arg_count + 1) * kPointerSize));
-  // Don't assign a type feedback id to the IC, since type feedback is provided
-  // by the vector above.
-  CallIC(ic);
+  if (expr->HasSpreadArguments()) {
+    CallFunctionFlags flags = call_type == CallICState::METHOD ?
+        CALL_AS_METHOD : NO_CALL_FUNCTION_FLAGS;
+    CallFunctionStub stub(isolate(), arg_count, flags, true);
+    __ movp(rdi, Operand(rsp, rax, times_pointer_size, kPointerSize));
+    __ CallStub(&stub);
+  } else {
+    Handle<Code> ic =
+        CodeFactory::CallIC(isolate(), arg_count, call_type).code();
+    __ Move(rdx, SmiFromSlot(expr->CallFeedbackICSlot()));
+
+    __ movp(rdi, Operand(rsp, (arg_count + 1) * kPointerSize));
+
+    // Don't assign a type feedback id to the IC, since type feedback is
+    // provided by the vector above.
+    CallIC(ic);
+  }
 
   RecordJSReturnSite(expr);
 
   // Restore context register.
   __ movp(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
   // Discard the function left on TOS.
   context()->DropAndPlug(1, rax);
 }
 
 
@@ skipping 2163 matching lines @@
   } else {
     Handle<Code> ic = CompareNilICStub::GetUninitialized(isolate(), nil);
     CallIC(ic, expr->CompareOperationFeedbackId());
     __ testp(rax, rax);
     Split(not_zero, if_true, if_false, fall_through);
   }
   context()->Plug(if_true, if_false);
 }
 
 
+void FullCodeGenerator::DoSpreadArgument(SpreadOperation* expr,
+                                         Register arg_count) {
+  Comment cmnt(masm_, "[ SpreadArgument");
+
+  Label loop, not_done, done;
+
+  __ decp(arg_count);
+  __ pushq(arg_count);
+
+  // var iterator = iterable[Symbol.iterator]();
+  VisitForEffect(expr->assign_iterator());
+
+  // Loop entry.
+  __ bind(&loop);
+
+  // result = iterator.next()
+  VisitForEffect(expr->next_result());
+
+  // if (result.done) break;
+  VisitForControl(expr->result_done(), &done, &not_done, &not_done);
+  __ bind(&not_done);
+
+  // %rax = result.value
+  VisitForAccumulatorValue(expr->result_value());

[arv (Not doing code reviews), 2015/02/12 21:41:34]

Why not VisitForStackValue?

[caitp (gmail), 2015/02/12 21:58:54]

right now, it's sort of like this:

before first value:
%rax -> ???
| <arg count from register> | ...

after getting value
| <arg count from register> | <arg count from previous stack value + 1>

after getting value and moving value to stack:
| iterator value            | <arg count>

after iterating, the stack has all the iterated values, and the arg count on the
end, so you just pop the arg count into the arg_count register. It seems to work
okay (but potentially breaks depending on what non-spread arguments are pushed,
though I haven't been able to find one that broke it).

I posted on v8-team-harmony asking about suggested ways to do this, because I'm
having trouble finding a register which won't get clobbered, so preserving the
count on the stack seems to be the only thing I can do. Suggestions are welcome!

+  __ pushq(Operand(rsp, 0));
+  __ incp(Operand(rsp, 0));
+  __ movp(Operand(rsp, 1 * kPointerSize), rax);
+
+  // loop
+  __ jmp(&loop);
+
+  __ bind(&done);
+  __ popq(arg_count);
+}
+
+
+void FullCodeGenerator::VisitSpreadOperation(SpreadOperation* expr) {
+  UNREACHABLE();
+}
+
+
 void FullCodeGenerator::VisitThisFunction(ThisFunction* expr) {
   __ movp(rax, Operand(rbp, JavaScriptFrameConstants::kFunctionOffset));
   context()->Plug(rax);
 }
 
 
 Register FullCodeGenerator::result_register() {
   return rax;
 }
 
@@ skipping 207 matching lines @@
   DCHECK_EQ(isolate->builtins()->OsrAfterStackCheck()->entry(),
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64