livetrax/libs/pbd/fpu.cc

/*
    Copyright (C) 2012 Paul Davis 

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program 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 this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/
#if !(defined (COMPILER_MSVC) || defined (COMPILER_MINGW))
#include "libpbd-config.h"

#define _XOPEN_SOURCE 600
#include <cstring> // for memset
#include <cstdlib>
#include <stdint.h>
#include <assert.h>

#include "pbd/fpu.h"
#include "pbd/error.h"

#include "i18n.h"

using namespace PBD;
using namespace std;

FPU::FPU ()
{
	unsigned long cpuflags = 0;

	_flags = Flags (0);

#if !( (defined __x86_64__) || (defined __i386__) ) // !ARCH_X86
	return;
#else

#ifndef _LP64 //USE_X86_64_ASM
	asm volatile (
		"mov $1, %%eax\n"
		"pushl %%ebx\n"
		"cpuid\n"
		"movl %%edx, %0\n"
		"popl %%ebx\n"
		: "=r" (cpuflags)
		: 
		: "%eax", "%ecx", "%edx"
		);
	
#else
	
	/* asm notes: although we explicitly save&restore rbx, we must tell
	   gcc that ebx,rbx is clobbered so that it doesn't try to use it as an intermediate
	   register when storing rbx. gcc 4.3 didn't make this "mistake", but gcc 4.4
	   does, at least on x86_64.
	*/

	asm volatile (
		"pushq %%rbx\n"
		"movq $1, %%rax\n"
		"cpuid\n"
		"movq %%rdx, %0\n"
		"popq %%rbx\n"
		: "=r" (cpuflags)
		: 
		: "%rax", "%rbx", "%rcx", "%rdx"
		);

#endif /* USE_X86_64_ASM */

	if (cpuflags & (1<<25)) {
		_flags = Flags (_flags | (HasSSE|HasFlushToZero));
	}

	if (cpuflags & (1<<26)) {
		_flags = Flags (_flags | HasSSE2);
	}

	if (cpuflags & (1 << 24)) {
		
		char** fxbuf = 0;
		
		/* DAZ wasn't available in the first version of SSE. Since
		   setting a reserved bit in MXCSR causes a general protection
		   fault, we need to be able to check the availability of this
		   feature without causing problems. To do this, one needs to
		   set up a 512-byte area of memory to save the SSE state to,
		   using fxsave, and then one needs to inspect bytes 28 through
		   31 for the MXCSR_MASK value. If bit 6 is set, DAZ is
		   supported, otherwise, it isn't.
		*/
		
#ifndef HAVE_POSIX_MEMALIGN
		fxbuf = (char **) malloc (sizeof (char *));
		assert (fxbuf);
		*fxbuf = (char *) malloc (512);
		assert (*fxbuf);
#else
		(void) posix_memalign ((void **) &fxbuf, 16, sizeof (char *));
		assert (fxbuf);
		(void) posix_memalign ((void **) fxbuf, 16, 512);
		assert (*fxbuf);
#endif			
		
		memset (*fxbuf, 0, 512);
		
		asm volatile (
			"fxsave (%0)"
			:
			: "r" (*fxbuf)
			: "memory"
			);
		
		uint32_t mxcsr_mask = *((uint32_t*) &((*fxbuf)[28]));
		
		/* if the mask is zero, set its default value (from intel specs) */
		
		if (mxcsr_mask == 0) {
			mxcsr_mask = 0xffbf;
		}
		
		if (mxcsr_mask & (1<<6)) {
			_flags = Flags (_flags | HasDenormalsAreZero);
		} 
		
		free (*fxbuf);
		free (fxbuf);
	}
#endif
}			

FPU::~FPU ()
{
}

#else  // COMPILER_MSVC
	const char* pbd_fpu = "pbd/msvc/fpu.cc takes precedence over this file";
#endif // COMPILER_MSVC