/* $OpenBSD: fenv.c,v 1.7 2022/12/27 17:10:07 jmc Exp $ */ /* $NetBSD: fenv.c,v 1.3 2010/08/01 06:34:38 taca 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/types.h> #include <sys/time.h> #include <sys/sysctl.h> #include <machine/cpu.h> #include <machine/npx.h> #include <fenv.h> /* * 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. */ fenv_t __fe_dfl_env = { { 0xffff0000 | __INITIAL_NPXCW__, /* Control word register */ 0xffff0000, /* Status word register */ 0xffffffff, /* Tag word register */ { 0x00000000, 0x00000000, 0x00000000, 0xffff0000 } }, __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 __test_sse(void) __attribute__ ((constructor)); static void __test_sse(void) { size_t oldlen = sizeof(__HAS_SSE); int mib[2] = { CTL_MACHDEP, CPU_SSE }; int rv; rv = sysctl(mib, 2, &__HAS_SSE, &oldlen, NULL, 0); if (rv == -1) __HAS_SSE = 0; } /* * The feclearexcept() function clears the supported floating-point exceptions * represented by `excepts'. */ int feclearexcept(int excepts) { fenv_t fenv; unsigned int mxcsr; excepts &= FE_ALL_EXCEPT; /* Store the current x87 floating-point environment */ __asm__ volatile ("fnstenv %0" : "=m" (fenv)); /* Clear the requested floating-point exceptions */ fenv.__x87.__status &= ~excepts; /* Load the x87 floating-point environment */ __asm__ volatile ("fldenv %0" : : "m" (fenv)); /* Same for SSE environment */ if (__HAS_SSE) { __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); mxcsr &= ~excepts; __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); } return (0); } DEF_STD(feclearexcept); /* * 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) { unsigned short status; unsigned int mxcsr = 0; excepts &= FE_ALL_EXCEPT; /* Store the current x87 status register */ __asm__ volatile ("fnstsw %0" : "=am" (status)); /* Store the MXCSR register */ if (__HAS_SSE) __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); /* Store the results in flagp */ *flagp = (status | mxcsr) & excepts; 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) { excepts &= FE_ALL_EXCEPT; fesetexceptflag((fexcept_t *)&excepts, excepts); __asm__ volatile ("fwait"); return (0); } DEF_STD(feraiseexcept); /* * 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 fenv; unsigned int mxcsr; excepts &= FE_ALL_EXCEPT; /* Store the current x87 floating-point environment */ __asm__ volatile ("fnstenv %0" : "=m" (fenv)); /* Set the requested status flags */ fenv.__x87.__status &= ~excepts; fenv.__x87.__status |= *flagp & excepts; /* Load the x87 floating-point environment */ __asm__ volatile ("fldenv %0" : : "m" (fenv)); /* Same for SSE environment */ if (__HAS_SSE) { __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); mxcsr &= ~excepts; mxcsr |= *flagp & excepts; __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); } return (0); } DEF_STD(fesetexceptflag); /* * 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) { unsigned short status; unsigned int mxcsr = 0; excepts &= FE_ALL_EXCEPT; /* Store the current x87 status register */ __asm__ volatile ("fnstsw %0" : "=am" (status)); /* Store the MXCSR register state */ if (__HAS_SSE) __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); return ((status | mxcsr) & excepts); } DEF_STD(fetestexcept); /* * The fegetround() function gets the current rounding direction. */ int fegetround(void) { unsigned short 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. */ __asm__ volatile ("fnstcw %0" : "=m" (control)); return (control & _X87_ROUND_MASK); } DEF_STD(fegetround); /* * The fesetround() function establishes 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) { unsigned short control; unsigned int mxcsr; /* Check whether requested rounding direction is supported */ if (round & ~_X87_ROUND_MASK) return (-1); /* Store the current x87 control word register */ __asm__ volatile ("fnstcw %0" : "=m" (control)); /* Set the rounding direction */ control &= ~_X87_ROUND_MASK; control |= round; /* Load the x87 control word register */ __asm__ volatile ("fldcw %0" : : "m" (control)); /* Same for the SSE environment */ if (__HAS_SSE) { __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); mxcsr &= ~(_X87_ROUND_MASK << _SSE_ROUND_SHIFT); mxcsr |= round << _SSE_ROUND_SHIFT; __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); } return (0); } DEF_STD(fesetround); /* * The fegetenv() function attempts to store the current floating-point * environment in the object pointed to by envp. */ int fegetenv(fenv_t *envp) { /* Store the current x87 floating-point environment */ __asm__ volatile ("fnstenv %0" : "=m" (*envp)); /* Store the MXCSR register state */ if (__HAS_SSE) __asm__ volatile ("stmxcsr %0" : "=m" (envp->__mxcsr)); /* * When an FNSTENV instruction is executed, all pending exceptions are * essentially lost (either the x87 FPU status register is cleared or * all exceptions are masked). * * 8.6 X87 FPU EXCEPTION SYNCHRONIZATION - * Intel(R) 64 and IA-32 Architectures Softare Developer's Manual - Vol1 */ __asm__ volatile ("fldcw %0" : : "m" (envp->__x87.__control)); return (0); } DEF_STD(fegetenv); /* * 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) { unsigned int mxcsr; /* Store the current x87 floating-point environment */ __asm__ volatile ("fnstenv %0" : "=m" (*envp)); /* Clear all exception flags in FPU */ __asm__ volatile ("fnclex"); if (__HAS_SSE) { /* Store the MXCSR register state */ __asm__ volatile ("stmxcsr %0" : "=m" (envp->__mxcsr)); /* Clear exception flags in MXCSR */ mxcsr = envp->__mxcsr; mxcsr &= ~FE_ALL_EXCEPT; /* Mask all exceptions */ mxcsr |= FE_ALL_EXCEPT << _SSE_MASK_SHIFT; /* Store the MXCSR register */ __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); } return (0); } DEF_STD(feholdexcept); /* * 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) { /* Load the x87 floating-point environment */ __asm__ volatile ("fldenv %0" : : "m" (*envp)); /* Store the MXCSR register */ if (__HAS_SSE) __asm__ volatile ("ldmxcsr %0" : : "m" (envp->__mxcsr)); return (0); } DEF_STD(fesetenv); /* * 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) { unsigned short status; unsigned int mxcsr = 0; /* Store the x87 status register */ __asm__ volatile ("fnstsw %0" : "=am" (status)); /* Store the MXCSR register */ if (__HAS_SSE) __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); /* Install new floating-point environment */ fesetenv(envp); /* Raise any previously accumulated exceptions */ feraiseexcept(status | mxcsr); return (0); } DEF_STD(feupdateenv); /* * The following functions are extensions to the standard */ int feenableexcept(int mask) { unsigned int mxcsr = 0, omask; unsigned short control; mask &= FE_ALL_EXCEPT; __asm__ volatile ("fnstcw %0" : "=m" (control)); if (__HAS_SSE) __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); omask = ~(control | (mxcsr >> _SSE_MASK_SHIFT)) & FE_ALL_EXCEPT; control &= ~mask; __asm__ volatile ("fldcw %0" : : "m" (control)); if (__HAS_SSE) { mxcsr &= ~(mask << _SSE_MASK_SHIFT); __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); } return (omask); } int fedisableexcept(int mask) { unsigned int mxcsr = 0, omask; unsigned short control; mask &= FE_ALL_EXCEPT; __asm__ volatile ("fnstcw %0" : "=m" (control)); if (__HAS_SSE) __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr)); omask = ~(control | (mxcsr >> _SSE_MASK_SHIFT)) & FE_ALL_EXCEPT; control |= mask; __asm__ volatile ("fldcw %0" : : "m" (control)); if (__HAS_SSE) { mxcsr |= mask << _SSE_MASK_SHIFT; __asm__ volatile ("ldmxcsr %0" : : "m" (mxcsr)); } return (omask); } int fegetexcept(void) { unsigned short control; /* * We assume that the masks for the x87 and the SSE unit are * the same. */ __asm__ volatile ("fnstcw %0" : "=m" (control)); return (~control & FE_ALL_EXCEPT); }
