/* $NetBSD: fenv.c,v 1.10 2021/09/03 21:54:59 andvar Exp $ */ /*- * Copyright (c) 2004-2005 David Schultz <das@FreeBSD.ORG> * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/cdefs.h> __RCSID("$NetBSD: fenv.c,v 1.10 2021/09/03 21:54:59 andvar Exp $"); #include "namespace.h" #include <sys/param.h> #include <sys/sysctl.h> #include <assert.h> #include <fenv.h> #include <stddef.h> #include <string.h> #ifdef __weak_alias __weak_alias(feclearexcept,_feclearexcept) __weak_alias(fedisableexcept,_fedisableexcept) __weak_alias(feenableexcept,_feenableexcept) __weak_alias(fegetenv,_fegetenv) __weak_alias(fegetexcept,_fegetexcept) __weak_alias(fegetexceptflag,_fegetexceptflag) __weak_alias(fegetround,_fegetround) __weak_alias(feholdexcept,_feholdexcept) __weak_alias(feraiseexcept,_feraiseexcept) __weak_alias(fesetenv,_fesetenv) __weak_alias(fesetexceptflag,_fesetexceptflag) __weak_alias(fesetround,_fesetround) __weak_alias(fetestexcept,_fetestexcept) __weak_alias(feupdateenv,_feupdateenv) #endif /* Load x87 Control Word */ #define __fldcw(__cw) __asm__ __volatile__ \ ("fldcw %0" : : "m" (__cw)) /* No-Wait Store Control Word */ #define __fnstcw(__cw) __asm__ __volatile__ \ ("fnstcw %0" : "=m" (*(__cw))) /* No-Wait Store Status Word */ #define __fnstsw(__sw) __asm__ __volatile__ \ ("fnstsw %0" : "=am" (*(__sw))) /* No-Wait Clear Exception Flags */ #define __fnclex() __asm__ __volatile__ \ ("fnclex") /* Load x87 Environment */ #define __fldenv(__env) __asm__ __volatile__ \ ("fldenv %0" : : "m" (__env)) /* No-Wait Store x87 environment */ #define __fnstenv(__env) __asm__ __volatile__ \ ("fnstenv %0" : "=m" (*(__env))) /* Check for and handle pending unmasked x87 pending FPU exceptions */ #define __fwait(__env) __asm__ __volatile__ \ ("fwait") /* Load the MXCSR register */ #define __ldmxcsr(__mxcsr) __asm__ __volatile__ \ ("ldmxcsr %0" : : "m" (__mxcsr)) /* Store the MXCSR register state */ #define __stmxcsr(__mxcsr) __asm__ __volatile__ \ ("stmxcsr %0" : "=m" (*(__mxcsr))) /* * The following constant represents the default floating-point environment * (that is, the one installed at program startup) and has type pointer to * const-qualified fenv_t. * * It can be used as an argument to the functions within the <fenv.h> header * that manage the floating-point environment, namely fesetenv() and * feupdateenv(). * * x87 fpu registers are 16bit wide. The upper bits, 31-16, are marked as * RESERVED. We provide a partial floating-point environment, where we * define only the lower bits. The reserved bits are extracted and set by the * consumers of FE_DFL_ENV, during runtime. */ fenv_t __fe_dfl_env = { .x87 = { .control = __NetBSD_NPXCW__, /* Control word register */ .unused1 = 0, /* Unused */ .status = 0, /* Status word register */ .unused2 = 0, /* Unused */ .tag = 0xffff, /* Tag word register */ .unused3 = 0, /* Unused */ .others = { 0, 0, 0, 0x0000ffff, } }, .mxcsr = __INITIAL_MXCSR__ /* MXCSR register */ }; /* * Test for SSE support on this processor. * * We need to use ldmxcsr/stmxcsr to get correct results if any part * of the program was compiled to use SSE floating-point, but we can't * use SSE on older processors. * * In order to do so, we need to query the processor capabilities via the CPUID * instruction. We can make it even simpler though, by querying the machdep.sse * sysctl. */ static int __HAS_SSE = 0; static void __init_libm(void) __attribute__ ((constructor, used)); static void __init_libm(void) { size_t oldlen = sizeof(__HAS_SSE); int rv; uint16_t control; rv = sysctlbyname("machdep.sse", &__HAS_SSE, &oldlen, NULL, 0); if (rv == -1) __HAS_SSE = 0; __fnstcw(&control); __fe_dfl_env.x87.control = control; } /* * The feclearexcept() function clears the supported floating-point exceptions * represented by `excepts'. */ int feclearexcept(int excepts) { fenv_t env; uint32_t mxcsr; int ex; _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); ex = excepts & FE_ALL_EXCEPT; /* It's ~3x faster to call fnclex, than store/load fp env */ if (ex == FE_ALL_EXCEPT) { __fnclex(); } else { __fnstenv(&env); env.x87.status &= ~ex; __fldenv(env); } if (__HAS_SSE) { __stmxcsr(&mxcsr); mxcsr &= ~ex; __ldmxcsr(mxcsr); } /* Success */ return (0); } /* * The fegetexceptflag() function stores an implementation-defined * representation of the states of the floating-point status flags indicated by * the argument excepts in the object pointed to by the argument flagp. */ int fegetexceptflag(fexcept_t *flagp, int excepts) { uint32_t mxcsr; uint16_t status; int ex; _DIAGASSERT(flagp != NULL); _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); ex = excepts & FE_ALL_EXCEPT; __fnstsw(&status); if (__HAS_SSE) __stmxcsr(&mxcsr); else mxcsr = 0; *flagp = (mxcsr | status) & ex; /* Success */ return (0); } /* * The feraiseexcept() function raises the supported floating-point exceptions * represented by the argument `excepts'. * * The standard explicitly allows us to execute an instruction that has the * exception as a side effect, but we choose to manipulate the status register * directly. * * The validation of input is being deferred to fesetexceptflag(). */ int feraiseexcept(int excepts) { fexcept_t ex; _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); ex = excepts & FE_ALL_EXCEPT; fesetexceptflag(&ex, excepts); __fwait(); /* Success */ return (0); } /* * This function sets the floating-point status flags indicated by the argument * `excepts' to the states stored in the object pointed to by `flagp'. It does * NOT raise any floating-point exceptions, but only sets the state of the flags. */ int fesetexceptflag(const fexcept_t *flagp, int excepts) { fenv_t env; uint32_t mxcsr; int ex; _DIAGASSERT(flagp != NULL); _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); ex = excepts & FE_ALL_EXCEPT; __fnstenv(&env); env.x87.status &= ~ex; env.x87.status |= *flagp & ex; __fldenv(env); if (__HAS_SSE) { __stmxcsr(&mxcsr); mxcsr &= ~ex; mxcsr |= *flagp & ex; __ldmxcsr(mxcsr); } /* Success */ return (0); } /* * The fetestexcept() function determines which of a specified subset of the * floating-point exception flags are currently set. The `excepts' argument * specifies the floating-point status flags to be queried. */ int fetestexcept(int excepts) { uint32_t mxcsr; uint16_t status; int ex; _DIAGASSERT((excepts & ~FE_ALL_EXCEPT) == 0); ex = excepts & FE_ALL_EXCEPT; __fnstsw(&status); if (__HAS_SSE) __stmxcsr(&mxcsr); else mxcsr = 0; return ((status | mxcsr) & ex); } int fegetround(void) { uint16_t control; /* * We assume that the x87 and the SSE unit agree on the * rounding mode. Reading the control word on the x87 turns * out to be about 5 times faster than reading it on the SSE * unit on an Opteron 244. */ __fnstcw(&control); return (control & __X87_ROUND_MASK); } /* * The fesetround() function shall establish the rounding direction represented * by its argument round. If the argument is not equal to the value of a * rounding direction macro, the rounding direction is not changed. */ int fesetround(int round) { uint32_t mxcsr; uint16_t control; if (round & ~__X87_ROUND_MASK) { /* Failure */ return (-1); } __fnstcw(&control); control &= ~__X87_ROUND_MASK; control |= round; __fldcw(control); if (__HAS_SSE) { __stmxcsr(&mxcsr); mxcsr &= ~(__X87_ROUND_MASK << __SSE_ROUND_SHIFT); mxcsr |= round << __SSE_ROUND_SHIFT; __ldmxcsr(mxcsr); } /* Success */ return (0); } /* * The fegetenv() function attempts to store the current floating-point * environment in the object pointed to by envp. */ int fegetenv(fenv_t *envp) { uint32_t mxcsr; _DIAGASSERT(flagp != NULL); /* * fnstenv masks all exceptions, so we need to restore the old control * word to avoid this side effect. */ __fnstenv(envp); __fldcw(envp->x87.control); if (__HAS_SSE) { __stmxcsr(&mxcsr); envp->mxcsr = mxcsr; } /* Success */ return (0); } /* * The feholdexcept() function saves the current floating-point environment in * the object pointed to by envp, clears the floating-point status flags, and * then installs a non-stop (continue on floating-point exceptions) mode, if * available, for all floating-point exceptions. */ int feholdexcept(fenv_t *envp) { uint32_t mxcsr; _DIAGASSERT(envp != NULL); __fnstenv(envp); __fnclex(); if (__HAS_SSE) { __stmxcsr(&mxcsr); envp->mxcsr = mxcsr; mxcsr &= ~FE_ALL_EXCEPT; mxcsr |= FE_ALL_EXCEPT << __SSE_EMASK_SHIFT; __ldmxcsr(mxcsr); } /* Success */ return (0); } /* * The fesetenv() function attempts to establish the floating-point environment * represented by the object pointed to by envp. The argument `envp' points * to an object set by a call to fegetenv() or feholdexcept(), or equal a * floating-point environment macro. The fesetenv() function does not raise * floating-point exceptions, but only installs the state of the floating-point * status flags represented through its argument. */ int fesetenv(const fenv_t *envp) { fenv_t env; _DIAGASSERT(envp != NULL); /* Store the x87 floating-point environment */ memset(&env, 0, sizeof(env)); __fnstenv(&env); __fe_dfl_env.x87.unused1 = env.x87.unused1; __fe_dfl_env.x87.unused2 = env.x87.unused2; __fe_dfl_env.x87.unused3 = env.x87.unused3; memcpy(__fe_dfl_env.x87.others, env.x87.others, sizeof(__fe_dfl_env.x87.others)); __fldenv(envp->x87); if (__HAS_SSE) __ldmxcsr(envp->mxcsr); /* Success */ return (0); } /* * The feupdateenv() function saves the currently raised floating-point * exceptions in its automatic storage, installs the floating-point environment * represented by the object pointed to by `envp', and then raises the saved * floating-point exceptions. The argument `envp' shall point to an object set * by a call to feholdexcept() or fegetenv(), or equal a floating-point * environment macro. */ int feupdateenv(const fenv_t *envp) { fenv_t env; uint32_t mxcsr; uint16_t status; _DIAGASSERT(envp != NULL); /* Store the x87 floating-point environment */ memset(&env, 0, sizeof(env)); __fnstenv(&env); __fe_dfl_env.x87.unused1 = env.x87.unused1; __fe_dfl_env.x87.unused2 = env.x87.unused2; __fe_dfl_env.x87.unused3 = env.x87.unused3; memcpy(__fe_dfl_env.x87.others, env.x87.others, sizeof(__fe_dfl_env.x87.others)); __fnstsw(&status); if (__HAS_SSE) __stmxcsr(&mxcsr); else mxcsr = 0; fesetenv(envp); feraiseexcept((mxcsr | status) & FE_ALL_EXCEPT); /* Success */ return (0); } /* * The following functions are extensions to the standard */ int feenableexcept(int mask) { uint32_t mxcsr, omask; uint16_t control; mask &= FE_ALL_EXCEPT; __fnstcw(&control); if (__HAS_SSE) __stmxcsr(&mxcsr); else mxcsr = 0; omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT; control &= ~mask; __fldcw(control); if (__HAS_SSE) { mxcsr &= ~(mask << __SSE_EMASK_SHIFT); __ldmxcsr(mxcsr); } return (FE_ALL_EXCEPT & ~omask); } int fedisableexcept(int mask) { uint32_t mxcsr, omask; uint16_t control; mask &= FE_ALL_EXCEPT; __fnstcw(&control); if (__HAS_SSE) __stmxcsr(&mxcsr); else mxcsr = 0; omask = (control | mxcsr >> __SSE_EMASK_SHIFT) & FE_ALL_EXCEPT; control |= mask; __fldcw(control); if (__HAS_SSE) { mxcsr |= mask << __SSE_EMASK_SHIFT; __ldmxcsr(mxcsr); } return (FE_ALL_EXCEPT & ~omask); } int fegetexcept(void) { uint16_t control; /* * We assume that the masks for the x87 and the SSE unit are * the same. */ __fnstcw(&control); return (~control & FE_ALL_EXCEPT); }
