spinlock.s

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; ***** BEGIN LICENSE BLOCK *****
; Source last modified: $Id: spinlock.s,v 1.1.30.3 2004/07/09 01:47:24 hubbe Exp $
; 
; // Portions Copyright (c) 1995-2003 RealNetworks, Inc. All Rights Reserved.
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//////////////////////////////////////////////////////////////////////
//
// spinlock.s
//      Implements a test-and-set operator, for use with a spinlock.
//      implemented in IA64 (Itanium) assembly.
//
// Implementation Notes:
//      A work-in-progress....
//
//////////////////////////////////////////////////////////////////////

  
//////////////////////////////////////////////////////////////////////
// Misc. Assembler Directives
//////////////////////////////////////////////////////////////////////

        .radix  C       // C-style numeric constants
        .section .text = "ax", "progbits" // read-only object code


//////////////////////////////////////////////////////////////////////
//
// _HXMutexSetBit
//      atomic test-and-set operator
//
// Interface:
//   extern "C" int _HXMutexSetBit(HX_MUTEX pLock);
//
// Inputs:
//   Paramaters:
//     in0 :  HX_MUTEX pLock  - pointer to mutex (integer) to modify
//
// Outputs:
//   Atomically modifies memory at *pLock:
//     *pLock = 1
//
//   Return value:
//     r8 : UINT32 - previous value of *pLock
//                   If zero, the lock attempt was successful
//
//////////////////////////////////////////////////////////////////////
	.proc   _HXMutexSetBit
	.global _HXMutexSetBit
_HXMutexSetBit:
        alloc           loc0 = ar.pfs, 1, 1, 0, 0 //one input, one local
	mov		r8 = 1;;                //x = 1
	xchg4		r8 = [in0], r8;;        //swap *pLock and x
	br.ret.dptk.few	rp;;                    //return previous *pLock value
        .endp   _HXMutexSetBit



//////////////////////////////////////////////////////////////////////
//
// _HXMutexClearBit
//      atomic bit clear operator
//
// Interface:
//   extern "C" void _HXMutexClearBit(HX_MUTEX pLock);
//
// Inputs:
//   Paramaters:
//     in0 :  HX_MUTEX pLock  - pointer to mutex (integer) to modify
//
// Outputs:
//   Atomically modifies memory at *pLock:
//     *pLock = 0
//
//   Return value:
//     none
//
//////////////////////////////////////////////////////////////////////
//
// Implementation notes:
// We cannot safely just set the lock to zero with an assignment, the
// use of the st4.rel release semantics is necessary to enforce correct
// memory ordering.
//
//////////////////////////////////////////////////////////////////////
        .proc   _HXMutexClearBit
        .global _HXMutexClearBit
_HXMutexClearBit:
        alloc           loc0 = ar.pfs, 1, 1, 0, 0 //one input, one local
        st4.rel         [in0] = r0;;            //atomically set to zero
	br.ret.dptk.few	rp;;                    //return
        .endp   _HXMutexClearBit