//++
// Copyright (c) 2006, Intel Corporation                                                         
// All rights reserved. This program and the accompanying materials                          
// are licensed and made available under the terms and conditions of the BSD License         
// which accompanies this distribution.  The full text of the license may be found at        
// http://opensource.org/licenses/bsd-license.php                                            
//                                                                                           
// THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     
// WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             
// 
// Module Name:
//
//   EbcLowLevel.s
//
// Abstract:
//
//   Contains low level routines for the Virtual Machine implementation
//   on an Itanium-based platform.
//
//
//--

.file  "EbcLowLevel.s"

#define PROCEDURE_ENTRY(name)   .##text;            \
                                .##type name, @function;    \
                                .##proc name;           \
name::

#define PROCEDURE_EXIT(name)    .##endp name

// Note: use of NESTED_SETUP requires number of locals (l) >= 3

#define NESTED_SETUP(i,l,o,r) \
         alloc loc1=ar##.##pfs,i,l,o,r ;\
         mov loc0=b0

#define NESTED_RETURN \
         mov b0=loc0 ;\
         mov ar##.##pfs=loc1 ;;\
         br##.##ret##.##dpnt  b0;;


//-----------------------------------------------------------------------------
//++
// EbcAsmLLCALLEX
//
//  Implements the low level EBC CALLEX instruction. Sets up the
//  stack pointer, does the spill of function arguments, and
//  calls the native function. On return it restores the original
//  stack pointer and returns to the caller.
//
// Arguments : 
//
// On Entry :
//    in0 = Address of native code to call
//    in1 = New stack pointer
//
// Return Value: 
// 
// As per static calling conventions. 
// 
//--
//---------------------------------------------------------------------------
;// void EbcAsmLLCALLEX (UINTN FunctionAddr, UINTN EbcStackPointer)
PROCEDURE_ENTRY(EbcAsmLLCALLEX)
  NESTED_SETUP (2,6,8,0)

  // NESTED_SETUP uses loc0 and loc1 for context save

  //
  // Save a copy of the EBC VM stack pointer
  //
  mov r8 = in1;;

  //
  // Copy stack arguments from EBC stack into registers. 
  // Assume worst case and copy 8.
  //
  ld8   out0 = [r8], 8;;
  ld8   out1 = [r8], 8;;
  ld8   out2 = [r8], 8;;
  ld8   out3 = [r8], 8;;
  ld8   out4 = [r8], 8;;
  ld8   out5 = [r8], 8;;
  ld8   out6 = [r8], 8;;
  ld8   out7 = [r8], 8;;

  //
  // Save the original stack pointer
  //
  mov   loc2 = r12;

  //
  // Save the gp
  //
  or    loc3 = r1, r0

  //
  // Set the new aligned stack pointer. Reserve space for the required 
  // 16-bytes of scratch area as well.
  //
  add  r12 = 48, in1

  //
  // Now call the function. Load up the function address from the descriptor
  // pointed to by in0. Then get the gp from the descriptor at the following
  // address in the descriptor.
  //
  ld8   r31 = [in0], 8;;
  ld8   r30 = [in0];;
  mov   b1 = r31
  mov   r1 = r30
  (p0) br.call.dptk.many b0 = b1;;

  //
  // Restore the original stack pointer and gp
  //
  mov   r12 = loc2
  or    r1 = loc3, r0

  //
  // Now return
  //
  NESTED_RETURN

PROCEDURE_EXIT(EbcAsmLLCALLEX)

//
// UINTN EbcLLGetEbcEntryPoint(VOID)
//
// Description:
//    Simply return, so that the caller retrieves the return register
//    contents (R8). That's where the thunk-to-ebc code stuffed the
//    EBC entry point.
//
PROCEDURE_ENTRY(EbcLLGetEbcEntryPoint)
    br.ret.sptk  b0 ;;
PROCEDURE_EXIT(EbcLLGetEbcEntryPoint)

//
// INT64 EbcLLGetReturnValue(VOID)
//
// Description:
//    This function is called to get the value returned by native code
//     to EBC. It simply returns because the return value should still
//    be in the register, so the caller just gets the unmodified value.
//
PROCEDURE_ENTRY(EbcLLGetReturnValue)
    br.ret.sptk  b0 ;;
PROCEDURE_EXIT(EbcLLGetReturnValue)

//
// UINTN EbcLLGetStackPointer(VOID)
//
PROCEDURE_ENTRY(EbcLLGetStackPointer)
    mov    r8 = r12 ;;
    br.ret.sptk  b0 ;;
    br.sptk.few b6 
PROCEDURE_EXIT(EbcLLGetStackPointer)