523 lines
12 KiB
C
523 lines
12 KiB
C
/* $NetBSD: fenv.c,v 1.3.8.1.6.1 2013/06/14 02:43:36 msaitoh Exp $ */
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/*-
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* Copyright (c) 2004-2005 David Schultz <das@FreeBSD.ORG>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: fenv.c,v 1.3.8.1.6.1 2013/06/14 02:43:36 msaitoh Exp $");
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#include <assert.h>
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#include <fenv.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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/* Load x87 Control Word */
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#define __fldcw(__cw) __asm__ __volatile__ \
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("fldcw %0" : : "m" (__cw))
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/* No-Wait Store Control Word */
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#define __fnstcw(__cw) __asm__ __volatile__ \
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("fnstcw %0" : "=m" (*(__cw)))
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/* No-Wait Store Status Word */
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#define __fnstsw(__sw) __asm__ __volatile__ \
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("fnstsw %0" : "=am" (*(__sw)))
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/* No-Wait Clear Exception Flags */
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#define __fnclex() __asm__ __volatile__ \
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("fnclex")
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/* Load x87 Environment */
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#define __fldenv(__env) __asm__ __volatile__ \
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("fldenv %0" : : "m" (__env))
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/* No-Wait Store x87 environment */
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#define __fnstenv(__env) __asm__ __volatile__ \
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("fnstenv %0" : "=m" (*(__env)))
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/* Check for and handle pending unmasked x87 pending FPU exceptions */
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#define __fwait(__env) __asm__ __volatile__ \
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("fwait")
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/* Load the MXCSR register */
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#define __ldmxcsr(__mxcsr) __asm__ __volatile__ \
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("ldmxcsr %0" : : "m" (__mxcsr))
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/* Store the MXCSR register state */
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#define __stmxcsr(__mxcsr) __asm__ __volatile__ \
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("stmxcsr %0" : "=m" (*(__mxcsr)))
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/*
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* The following constant represents the default floating-point environment
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* (that is, the one installed at program startup) and has type pointer to
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* const-qualified fenv_t.
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*
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* It can be used as an argument to the functions within the <fenv.h> header
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* that manage the floating-point environment, namely fesetenv() and
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* feupdateenv().
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*
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* x87 fpu registers are 16bit wide. The upper bits, 31-16, are marked as
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* RESERVED. We provide a partial floating-point environment, where we
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* define only the lower bits. The reserved bits are extracted and set by the
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* consumers of FE_DFL_ENV, during runtime.
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*/
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fenv_t __fe_dfl_env = {
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{
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__NetBSD_NPXCW__, /* Control word register */
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0x0, /* Unused */
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0x0000, /* Status word register */
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0x0, /* Unused */
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0x0000ffff, /* Tag word register */
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0x0, /* Unused */
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{
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0x0000, 0x0000,
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0x0000, 0xffff
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}
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},
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__INITIAL_MXCSR__ /* MXCSR register */
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};
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/*
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* Test for SSE support on this processor.
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*
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* We need to use ldmxcsr/stmxcsr to get correct results if any part
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* of the program was compiled to use SSE floating-point, but we can't
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* use SSE on older processors.
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*
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* In order to do so, we need to query the processor capabilities via the CPUID
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* instruction. We can make it even simpler though, by querying the machdep.sse
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* sysctl.
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*/
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static int __HAS_SSE = 0;
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static void __test_sse(void) __attribute__ ((constructor));
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static void __test_sse(void)
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{
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#if 0
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size_t oldlen = sizeof(__HAS_SSE);
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int rv;
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/* TODO: Properly detect whether see is available! */
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rv = sysctlbyname("machdep.sse", &__HAS_SSE, &oldlen, NULL, 0);
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if (rv == -1)
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__HAS_SSE = 0;
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#elif defined(__SSE__)
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__HAS_SSE = 1;
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#elif defined(__sortix__)
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__HAS_SSE = 1; /* Currently unconditionally enabled and needed to boot. */
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#else
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__HAS_SSE = 0;
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#endif
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}
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/*
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* The feclearexcept() function clears the supported floating-point exceptions
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* represented by `excepts'.
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*/
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int
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feclearexcept(int excepts)
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{
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fenv_t env;
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uint32_t mxcsr;
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int ex;
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assert((excepts & ~FE_ALL_EXCEPT) == 0);
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ex = excepts & FE_ALL_EXCEPT;
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/* It's ~3x faster to call fnclex, than store/load fp env */
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if (ex == FE_ALL_EXCEPT) {
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__fnclex();
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} else {
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__fnstenv(&env);
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env.x87.status &= ~ex;
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__fldenv(env);
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}
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if (__HAS_SSE) {
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__stmxcsr(&mxcsr);
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mxcsr &= ~ex;
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__ldmxcsr(mxcsr);
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}
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/* Success */
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return (0);
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}
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/*
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* The fegetexceptflag() function stores an implementation-defined
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* representation of the states of the floating-point status flags indicated by
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* the argument excepts in the object pointed to by the argument flagp.
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*/
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int
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fegetexceptflag(fexcept_t *flagp, int excepts)
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{
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uint32_t mxcsr;
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uint16_t status;
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int ex;
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assert(flagp != NULL);
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assert((excepts & ~FE_ALL_EXCEPT) == 0);
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ex = excepts & FE_ALL_EXCEPT;
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__fnstsw(&status);
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if (__HAS_SSE)
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__stmxcsr(&mxcsr);
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else
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mxcsr = 0;
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*flagp = (mxcsr | status) & ex;
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/* Success */
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return (0);
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}
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/*
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* The feraiseexcept() function raises the supported floating-point exceptions
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* represented by the argument `excepts'.
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*
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* The standard explicitly allows us to execute an instruction that has the
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* exception as a side effect, but we choose to manipulate the status register
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* directly.
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*
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* The validation of input is being deferred to fesetexceptflag().
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*/
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int
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feraiseexcept(int excepts)
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{
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fexcept_t ex;
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assert((excepts & ~FE_ALL_EXCEPT) == 0);
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ex = excepts & FE_ALL_EXCEPT;
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fesetexceptflag(&ex, excepts);
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__fwait();
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/* Success */
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return (0);
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}
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/*
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* This function sets the floating-point status flags indicated by the argument
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* `excepts' to the states stored in the object pointed to by `flagp'. It does
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* NOT raise any floating-point exceptions, but only sets the state of the flags.
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*/
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int
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fesetexceptflag(const fexcept_t *flagp, int excepts)
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{
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fenv_t env;
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uint32_t mxcsr;
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int ex;
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assert(flagp != NULL);
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assert((excepts & ~FE_ALL_EXCEPT) == 0);
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ex = excepts & FE_ALL_EXCEPT;
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__fnstenv(&env);
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env.x87.status &= ~ex;
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env.x87.status |= *flagp & ex;
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__fldenv(env);
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if (__HAS_SSE) {
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__stmxcsr(&mxcsr);
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mxcsr &= ~ex;
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mxcsr |= *flagp & ex;
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__ldmxcsr(mxcsr);
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}
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/* Success */
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return (0);
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}
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/*
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* The fetestexcept() function determines which of a specified subset of the
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* floating-point exception flags are currently set. The `excepts' argument
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* specifies the floating-point status flags to be queried.
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*/
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int
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fetestexcept(int excepts)
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{
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uint32_t mxcsr;
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uint16_t status;
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int ex;
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assert((excepts & ~FE_ALL_EXCEPT) == 0);
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ex = excepts & FE_ALL_EXCEPT;
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__fnstsw(&status);
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if (__HAS_SSE)
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__stmxcsr(&mxcsr);
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else
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mxcsr = 0;
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return ((status | mxcsr) & ex);
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}
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int
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fegetround(void)
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{
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uint16_t control;
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/*
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* We assume that the x87 and the SSE unit agree on the
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* rounding mode. Reading the control word on the x87 turns
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* out to be about 5 times faster than reading it on the SSE
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* unit on an Opteron 244.
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*/
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__fnstcw(&control);
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return (control & __X87_ROUND_MASK);
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}
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/*
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* The fesetround() function shall establish the rounding direction represented
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* by its argument round. If the argument is not equal to the value of a
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* rounding direction macro, the rounding direction is not changed.
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*/
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int
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fesetround(int round)
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{
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uint32_t mxcsr;
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uint16_t control;
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if (round & ~__X87_ROUND_MASK) {
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/* Failure */
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return (-1);
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}
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__fnstcw(&control);
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control &= ~__X87_ROUND_MASK;
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control |= round;
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__fldcw(control);
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if (__HAS_SSE) {
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__stmxcsr(&mxcsr);
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mxcsr &= ~(__X87_ROUND_MASK << __SSE_ROUND_SHIFT);
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mxcsr |= round << __SSE_ROUND_SHIFT;
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__ldmxcsr(mxcsr);
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}
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/* Success */
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return (0);
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}
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/*
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* The fegetenv() function attempts to store the current floating-point
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* environment in the object pointed to by envp.
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*/
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int
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fegetenv(fenv_t *envp)
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{
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uint32_t mxcsr;
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assert(envp != NULL);
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/*
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* fnstenv masks all exceptions, so we need to restore the old control
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* word to avoid this side effect.
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*/
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__fnstenv(envp);
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__fldcw(envp->x87.control);
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if (__HAS_SSE) {
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__stmxcsr(&mxcsr);
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envp->mxcsr = mxcsr;
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}
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/* Success */
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return (0);
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}
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/*
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* The feholdexcept() function saves the current floating-point environment in
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* the object pointed to by envp, clears the floating-point status flags, and
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* then installs a non-stop (continue on floating-point exceptions) mode, if
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* available, for all floating-point exceptions.
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*/
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int
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feholdexcept(fenv_t *envp)
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{
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uint32_t mxcsr;
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assert(envp != NULL);
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__fnstenv(envp);
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__fnclex();
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if (__HAS_SSE) {
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__stmxcsr(&mxcsr);
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envp->mxcsr = mxcsr;
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mxcsr &= ~FE_ALL_EXCEPT;
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mxcsr |= FE_ALL_EXCEPT << __SSE_EMASK_SHIFT;
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__ldmxcsr(mxcsr);
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}
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/* Success */
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return (0);
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}
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/*
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* The fesetenv() function attempts to establish the floating-point environment
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* represented by the object pointed to by envp. The argument `envp' points
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* to an object set by a call to fegetenv() or feholdexcept(), or equal a
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* floating-point environment macro. The fesetenv() function does not raise
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* floating-point exceptions, but only installs the state of the floating-point
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* status flags represented through its argument.
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*/
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int
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fesetenv(const fenv_t *envp)
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{
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fenv_t env;
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assert(envp != NULL);
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/* Store the x87 floating-point environment */
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memset(&env, 0, sizeof(env));
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__fnstenv(&env);
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__fe_dfl_env.x87.unused1 = env.x87.unused1;
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__fe_dfl_env.x87.unused2 = env.x87.unused2;
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__fe_dfl_env.x87.unused3 = env.x87.unused3;
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memcpy(__fe_dfl_env.x87.others,
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env.x87.others,
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sizeof(__fe_dfl_env.x87.others) / sizeof(uint32_t));
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__fldenv(envp->x87);
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if (__HAS_SSE)
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__ldmxcsr(envp->mxcsr);
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/* Success */
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return (0);
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}
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/*
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* The feupdateenv() function saves the currently raised floating-point
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* exceptions in its automatic storage, installs the floating-point environment
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* represented by the object pointed to by `envp', and then raises the saved
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* floating-point exceptions. The argument `envp' shall point to an object set
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* by a call to feholdexcept() or fegetenv(), or equal a floating-point
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* environment macro.
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*/
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int
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feupdateenv(const fenv_t *envp)
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{
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fenv_t env;
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uint32_t mxcsr;
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uint16_t status;
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assert(envp != NULL);
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/* Store the x87 floating-point environment */
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memset(&env, 0, sizeof(env));
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__fnstenv(&env);
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__fe_dfl_env.x87.unused1 = env.x87.unused1;
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__fe_dfl_env.x87.unused2 = env.x87.unused2;
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__fe_dfl_env.x87.unused3 = env.x87.unused3;
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memcpy(__fe_dfl_env.x87.others,
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env.x87.others,
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sizeof(__fe_dfl_env.x87.others) / sizeof(uint32_t));
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__fnstsw(&status);
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if (__HAS_SSE)
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__stmxcsr(&mxcsr);
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else
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mxcsr = 0;
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fesetenv(envp);
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feraiseexcept((mxcsr | status) & FE_ALL_EXCEPT);
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/* Success */
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return (0);
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}
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/*
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* The following functions are extentions to the standard
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*/
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int
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feenableexcept(int mask)
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{
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uint32_t mxcsr, omask;
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uint16_t control;
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mask &= FE_ALL_EXCEPT;
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__fnstcw(&control);
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if (__HAS_SSE)
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__stmxcsr(&mxcsr);
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else
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mxcsr = 0;
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omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT;
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control &= ~mask;
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__fldcw(control);
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if (__HAS_SSE) {
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mxcsr &= ~(mask << __SSE_EMASK_SHIFT);
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__ldmxcsr(mxcsr);
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}
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return (FE_ALL_EXCEPT & ~omask);
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}
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int
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fedisableexcept(int mask)
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{
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uint32_t mxcsr, omask;
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uint16_t control;
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mask &= FE_ALL_EXCEPT;
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__fnstcw(&control);
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if (__HAS_SSE)
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__stmxcsr(&mxcsr);
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else
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mxcsr = 0;
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omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT;
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control |= mask;
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__fldcw(control);
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if (__HAS_SSE) {
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mxcsr |= mask << __SSE_EMASK_SHIFT;
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__ldmxcsr(mxcsr);
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}
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return (FE_ALL_EXCEPT & ~omask);
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}
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int
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fegetexcept(void)
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{
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uint16_t control;
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/*
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* We assume that the masks for the x87 and the SSE unit are
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* the same.
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*/
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__fnstcw(&control);
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return (~control & FE_ALL_EXCEPT);
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}
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