linux x86 assembler to llvm assembler

Question

I'm trying to translate linux x86 assembler to llvm assembler.

Actually, I don't get any assembler, Is it possible to translate or decompile GNU assembler to llvm assembler?

If any, what is the tool?

or need to decompile and assemble with clang?

----------- os_Linux_x86.s in NSPR :

// -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// 
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

// PRInt32 _PR_x86_AtomicIncrement(PRInt32 *val)
//
// Atomically increment the integer pointed to by 'val' and return
// the result of the increment.
//
    .text
    .globl _PR_x86_AtomicIncrement
    .align 4
_PR_x86_AtomicIncrement:
    movl 4(%esp), %ecx
    movl $1, %eax
    lock
    xaddl %eax, (%ecx)
    incl %eax
    ret

......