/*************************************************************************
 * Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com>               *
 *                                                                       *
 * This file is part of The Sandglass Library.                           *
 *                                                                       *
 * The Sandglass Library is free software; you can redistribute it       *
 * and/or modify it under the terms of the GNU Lesser General Public     *
 * License as published by the Free Software Foundation; either version  *
 * 3 of the License, or (at your option) any later version.              *
 *                                                                       *
 * The Sandglass Library is distributed in the hope that it will be      *
 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
 * Lesser General Public License for more details.                       *
 *                                                                       *
 * You should have received a copy of the GNU Lesser General Public      *
 * License along with this program.  If not, see                         *
 * <http://www.gnu.org/licenses/>.                                       *
 *************************************************************************/

/*
 * Return the time stamp counter, and serialize the instruction
 */

        .text
/* long sandglass_get_tsc(); */
.globl sandglass_get_tsc
        .type sandglass_get_tsc, @function
sandglass_get_tsc:
        movq %rbx, %rdi         /* Callee-save register, clobbered by cpuid */
        xorl %eax, %eax         /* Make cpuid do a consistent operation */
        cpuid                   /* Serialize */
        rdtsc                   /* Read time stamp counter */
        shlq $32, %rdx
        orq %rdx, %rax
        movq %rax, %rsi
        xorl %eax, %eax
        cpuid                   /* Serialize again */
        movq %rsi, %rax
        movq %rdi, %rbx
        ret
        .size sandglass_get_tsc, .-sandglass_get_tsc

/*
 * Return the granularity of the TSC
 */

/* unsigned int sandglass_tsc_loops(); */
.globl sandglass_tsc_loops
        .type sandglass_tsc_loops, @function
sandglass_tsc_loops:
        rdtsc                   /* Read time stamp counter */
        movl %eax, %ecx
.Lrdtsc:
        rdtsc                   /* Read counter again */
        subl %ecx, %eax
        jz .Lrdtsc              /* If we got the same value, try again */
        ret
        .size sandglass_tsc_loops, .-sandglass_tsc_loops