Add support for leaf runtime calls

vm/stub_code_ia32.cc

Index: vm/stub_code_ia32.cc
===================================================================
--- vm/stub_code_ia32.cc	(revision 8520)
+++ vm/stub_code_ia32.cc	(working copy)
@@ -88,6 +88,49 @@
 }
 
 
+// Input parameters:
+//   ESP : points to return address.
+//   ESP + 4 : address of last argument in argument array.
+//   ESP + 4*EDX : address of first argument in argument array.
+//   ESP + 4*EDX + 4 : address of return value.
+//   ECX : address of the runtime function to call.
+//   EDX : number of arguments to the call.
+// Must preserve callee saved registers EDI and EBX.
+void StubCode::GenerateCallToLeafRuntimeStub(Assembler* assembler) {
+  const intptr_t isolate_offset = NativeArguments::isolate_offset();
+  const intptr_t argc_offset = NativeArguments::argc_offset();
+  const intptr_t argv_offset = NativeArguments::argv_offset();
+
+  __ EnterFrame(0);

[srdjan, 2012/06/12 20:10:41]

Why do you need the frame enter and leave? No stack traversal can occur here

[siva, 2012/06/12 21:18:04]

Yes, I would love to get rid of this too, but the stack alignment done below
leaves us with a not so easy way of restoring the stack pointer after the call,
hence the EnterFrame.



On 2012/06/12 20:10:41, srdjan wrote:

+
+  // Reserve space for arguments and align frame before entering C++ world.
+  __ AddImmediate(ESP, Immediate(-sizeof(NativeArguments)));
+  if (OS::ActivationFrameAlignment() > 0) {
+    __ andl(ESP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
+  }
+
+  // Pass NativeArguments structure by value.
+  // NOTE: the retvalue area in the NativeArguments structure is not setup
+  //       as leaf routines return the value in EAX.
+  __ movl(EAX, FieldAddress(CTX, Context::isolate_offset()));
+  __ movl(Address(ESP, isolate_offset), EAX);  // Set isolate in NativeArgs.
+  __ movl(Address(ESP, argc_offset), EDX);  // Set argc in NativeArguments.
+  __ leal(EAX, Address(EBP, EDX, TIMES_4, 1 * kWordSize));  // Compute argv.
+  __ movl(Address(ESP, argv_offset), EAX);  // Set argv in NativeArguments.
+
+  // Make call to leaf runtime entry.
+  __ call(ECX);
+
+  // Set return value in caller's frame.
+  __ movl(ECX, Address(ESP, argv_offset));
+  __ addl(ECX, Immediate(1 * kWordSize));  // Retval is next to 1st argument.
+  __ movl(Address(ECX, 0), EAX);
+
+  __ LeaveFrame();
+  __ ret();
+}
+
+
 // Print the stop message.
 static void PrintStopMessage(const char* message) {
   OS::Print("Stop message: %s\n", message);