/*
    Copyright 2005-2015 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks. Threading Building Blocks is free software;
    you can redistribute it and/or modify it under the terms of the GNU General Public License
    version 2  as  published  by  the  Free Software Foundation.  Threading Building Blocks 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 General Public License for more details.   You should have received a copy of
    the  GNU General Public License along with Threading Building Blocks; if not, write to the
    Free Software Foundation, Inc.,  51 Franklin St,  Fifth Floor,  Boston,  MA 02110-1301 USA

    As a special exception,  you may use this file  as part of a free software library without
    restriction.  Specifically,  if other files instantiate templates  or use macros or inline
    functions from this file, or you compile this file and link it with other files to produce
    an executable,  this file does not by itself cause the resulting executable to be covered
    by the GNU General Public License. This exception does not however invalidate any other
    reasons why the executable file might be covered by the GNU General Public License.
*/

#ifndef __TBB_machine_gcc_ia32_common_H
#define __TBB_machine_gcc_ia32_common_H

//TODO: Add a higher-level function, e.g. tbb::interal::log2(), into tbb_stddef.h, which
//uses __TBB_Log2 and contains the assert and remove the assert from here and all other
//platform-specific headers.
//TODO: Check if use of gcc intrinsic gives a better chance for cross call optimizations
template <typename T>
static inline intptr_t __TBB_machine_lg( T x ) {
    __TBB_ASSERT(x>0, "The logarithm of a non-positive value is undefined.");
    uintptr_t j, i = x;
    __asm__("bsr %1,%0" : "=r"(j) : "r"(i));
    return j;
}
#define __TBB_Log2(V)  __TBB_machine_lg(V)

#ifndef __TBB_Pause
//TODO: check if raising a ratio of pause instructions to loop control instructions
//(via e.g. loop unrolling) gives any benefit for HT.  E.g, the current implementation
//does about 2 CPU-consuming instructions for every pause instruction.  Perhaps for
//high pause counts it should use an unrolled loop to raise the ratio, and thus free
//up more integer cycles for the other hyperthread.  On the other hand, if the loop is
//unrolled too far, it won't fit in the core's loop cache, and thus take away
//instruction decode slots from the other hyperthread.

//TODO: check if use of gcc __builtin_ia32_pause intrinsic gives a "some how" better performing code
static inline void __TBB_machine_pause( int32_t delay ) {
    for (int32_t i = 0; i < delay; i++) {
       __asm__ __volatile__("pause;");
    }
    return;
}
#define __TBB_Pause(V) __TBB_machine_pause(V)
#endif /* !__TBB_Pause */

// API to retrieve/update FPU control setting
#ifndef __TBB_CPU_CTL_ENV_PRESENT
#define __TBB_CPU_CTL_ENV_PRESENT 1
namespace tbb {
namespace internal {
class cpu_ctl_env {
private:
    int     mxcsr;
    short   x87cw;
    static const int MXCSR_CONTROL_MASK = ~0x3f; /* all except last six status bits */
public:
    bool operator!=( const cpu_ctl_env& ctl ) const { return mxcsr != ctl.mxcsr || x87cw != ctl.x87cw; }
    void get_env() {
    #if __TBB_ICC_12_0_INL_ASM_FSTCW_BROKEN
        cpu_ctl_env loc_ctl;
        __asm__ __volatile__ (
                "stmxcsr %0\n\t"
                "fstcw %1"
                : "=m"(loc_ctl.mxcsr), "=m"(loc_ctl.x87cw)
        );
        *this = loc_ctl;
    #else
        __asm__ __volatile__ (
                "stmxcsr %0\n\t"
                "fstcw %1"
                : "=m"(mxcsr), "=m"(x87cw)
        );
    #endif
        mxcsr &= MXCSR_CONTROL_MASK;
    }
    void set_env() const {
        __asm__ __volatile__ (
                "ldmxcsr %0\n\t"
                "fldcw %1"
                : : "m"(mxcsr), "m"(x87cw)
        );
    }
};
} // namespace internal
} // namespace tbb
#endif /* !__TBB_CPU_CTL_ENV_PRESENT */

#include "gcc_itsx.h"

#endif /* __TBB_machine_gcc_ia32_common_H */
