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

runtime/vm/stub_code_x64.cc

Index: runtime/vm/stub_code_x64.cc
diff --git a/runtime/vm/stub_code_x64.cc b/runtime/vm/stub_code_x64.cc
index a9d37774359b79ddd33f53a1694a47713f6be9bc..09286ed9ac356c4e9c12e5c75b6a1b13ba17126b 100644
--- a/runtime/vm/stub_code_x64.cc
+++ b/runtime/vm/stub_code_x64.cc
@@ -765,12 +765,15 @@ void StubCode::GenerateCallClosureFunctionStub(Assembler* assembler) {
 //   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.
@@ -778,7 +781,8 @@ void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   __ 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
@@ -866,14 +870,14 @@ void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   __ 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();
 }