Setup the pool pointer when entering Dart from C++ so the intrinsic functions may rely on it being …

runtime/vm/stub_code_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 747 matching lines @@
 
 // Called when invoking Dart code from C++ (VM code).
 // Input parameters:
 //   RSP : points to return address.
 //   RDI : entrypoint of the Dart function to call.
 //   RSI : arguments descriptor array.
 //   RDX : arguments array.
 //   RCX : new context containing the current isolate pointer.
 void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   // Save frame pointer coming in.
-  __ EnterStubFrame();
+  __ EnterStubFrameWithPP();
+
+  // The old frame pointer, the return address, the old R15 (for PP).
+  const intptr_t kInitiallyPushedSlots = 3;

[siva, 2013/09/19 00:45:37]

Not sure if kInitiallyPushedSlots is a good name, maybe
const int kInitialOffset = 3?

And the comment could include this stack layout structure

              | saved PP           |
              | callee's PC marker |
              | saved RBP          |    (RBP of current frame)
              | saved PC           |    (PC of current frame)
                                        <- RSP of current frame

[zra, 2013/09/19 00:55:22]

+1

[rmacnak, 2013/09/19 16:57:36]

This stack looks upside down to me.

  __ EnterStubFrameWithPP();

  // At this point, the stack looks like:
  // | saved PC (return to DartEntry::InvokeFunction) |  
  // | saved RBP                                      | <-- RBP
  // | "saved PC area" = 0                            |
  // | saved RC15/PP                                  | <-- RSP

What is the middle value, what you labelled as "callee's PC marker" and what the
code calls "the saved PC area"? It looks like it is being used to find the
RawCode associated with a frame, so for the stub frame it will remain null?

 
   // Save arguments descriptor array and new context.
-  const intptr_t kArgumentsDescOffset = -2 * kWordSize;
+  const intptr_t kArgumentsDescOffset = -(kInitiallyPushedSlots) * kWordSize;
   __ pushq(RSI);
-  const intptr_t kNewContextOffset = -3 * kWordSize;
+  const intptr_t kNewContextOffset = -(kInitiallyPushedSlots + 1) * kWordSize;
   __ pushq(RCX);
 
   // Save C++ ABI callee-saved registers.
   __ pushq(RBX);
   __ pushq(R12);
   __ pushq(R13);
   __ pushq(R14);
-  __ pushq(R15);
+  // R15 is already saved above by EnterStubFrameWithPP.

[rmacnak, 2013/09/18 21:04:24]

Actually, we MUST not save R15 again, because it changes the offsets of the
Context pointer and exit frame info pushed below.

[siva, 2013/09/19 00:45:37]

True, the comment is to make sure we document that all the 
callee-saved registers per the C++ ABI are indeed saved.

(if you want you can add a comment that the offsets below of context pointer,
exit frame etc, need to be changed if additional values are pushed on the
stack).

On 2013/09/18 21:04:24, Ryan Macnak wrote:

+
 
   // The new Context structure contains a pointer to the current Isolate
   // structure. Cache the Context pointer in the CTX register so that it is
   // available in generated code and calls to Isolate::Current() need not be
   // done. The assumption is that this register will never be clobbered by
   // compiled or runtime stub code.
 
   // Cache the new Context pointer into CTX while executing Dart code.
   __ movq(CTX, Address(RCX, VMHandles::kOffsetOfRawPtrInHandle));
 
@@ skipping 67 matching lines @@
   // Uses RCX as a temporary register for this.
   __ popq(RCX);
   __ movq(Address(CTX, Isolate::top_context_offset()), RCX);
 
   // Restore the saved top exit frame info back into the Isolate structure.
   // Uses RDX as a temporary register for this.
   __ popq(RDX);
   __ movq(Address(CTX, Isolate::top_exit_frame_info_offset()), RDX);
 
   // Restore C++ ABI callee-saved registers.
-  __ popq(R15);
+  // R15 will be restored below by LeaveFrameWithPP.
   __ popq(R14);
   __ popq(R13);
   __ popq(R12);
   __ popq(RBX);
 
   // Restore the frame pointer.
-  __ LeaveFrame();
+  __ LeaveFrameWithPP();
 
   __ ret();
 }
 
 
 // Called for inline allocation of contexts.
 // Input:
 // R10: number of context variables.
 // Output:
 // RAX: new allocated RawContext object.
@@ skipping 1333 matching lines @@
   __ movq(right, Address(RSP, 3 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right);
   __ popq(right);
   __ popq(left);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64