root/src/cmd/dist/arm.c

DEFINITIONS

1. xgetgoarm
2. xgetgoarm
3. useVFPv3
4. useVFPv1

// Copyright 2012 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include "a.h"

#ifndef __ARMEL__
char *
xgetgoarm(void)
{
        return "6";
}
#else
static void useVFPv3(void);
static void useVFPv1(void);

char *
xgetgoarm(void)
{
#if defined(__FreeBSD__)
        // FreeBSD has broken VFP support
        return "5";
#endif
        if(xtryexecfunc(useVFPv3))
                return "7";
        else if(xtryexecfunc(useVFPv1))
                return "6";
        return "5";
}

static void
useVFPv3(void)
{
        // try to run VFPv3-only "vmov.f64 d0, #112" instruction
        // we can't use that instruction directly, because we
        // might be compiling with a soft-float only toolchain.
        //
        // some newer toolchains are configured to use thumb
        // by default, so we need to do some mode changing magic
        // here.
        // We can use "bx pc; nop" here, but GNU as(1) insists
        // on warning us
        // "use of r15 in bx in ARM mode is not really useful"
        // so we workaround that by using "bx r0"
        __asm__ __volatile__ ("mov r0, pc");
        __asm__ __volatile__ ("bx r0");
        __asm__ __volatile__ (".word 0xeeb70b00"); // vmov.f64 d0, #112
        __asm__ __volatile__ (".word 0xe12fff1e"); // bx lr
}

static void
useVFPv1(void)
{
        // try to run "vmov.f64 d0, d0" instruction
        // we can't use that instruction directly, because we
        // might be compiling with a soft-float only toolchain
        //
        // some newer toolchains are configured to use thumb
        // by default, so we need to do some mode changing magic
        // here.
        // We can use "bx pc; nop" here, but GNU as(1) insists
        // on warning us
        // "use of r15 in bx in ARM mode is not really useful"
        // so we workaround that by using "bx r0"
        __asm__ __volatile__ ("mov r0, pc");
        __asm__ __volatile__ ("bx r0");
        __asm__ __volatile__ (".word 0xeeb00b40"); // vomv.f64 d0, d0
        __asm__ __volatile__ (".word 0xe12fff1e"); // bx lr
}

#endif