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https://github.com/jart/cosmopolitan.git
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96 lines
4 KiB
C
96 lines
4 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2024 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/runtime/fenv.h"
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/**
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* Enables floating point exception trapping, e.g.
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*
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* feenableexcept(FE_INVALID | FE_DIVBYZERO |
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* FE_OVERFLOW | FE_UNDERFLOW);
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*
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* When trapping is enabled, something should handle SIGFPE. Calling
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* ShowCrashReports() at startup will install a generic handler with
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* backtraces and the symbol of the `si->si_code` which UNIX defines
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*
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* - `FPE_INTOVF`: integer overflow
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* - `FPE_INTDIV`: integer divide by zero
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* - `FPE_FLTDIV`: floating point divide by zero
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* - `FPE_FLTOVF`: floating point overflow
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* - `FPE_FLTUND`: floating point underflow
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* - `FPE_FLTRES`: floating point inexact
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* - `FPE_FLTINV`: invalid floating point operation
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* - `FPE_FLTSUB`: subscript out of range
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*
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* It's important to not use the `-ffast-math` or `-Ofast` flags when
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* compiling code that needs to be debugged. Using `-fsignaling-nans`
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* will also help, since GCC doesn't enable that by default.
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*
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* @param excepts may bitwise-or the following:
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* - `FE_INVALID`
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* - `FE_DIVBYZERO`
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* - `FE_OVERFLOW`
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* - `FE_UNDERFLOW`
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* - `FE_INEXACT`
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* - `FE_ALL_EXCEPT` (all of the above)
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* @see fetestexcept() if you don't want to deal with signals
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* @see fedisableexcept() to turn it back off again
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*/
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int feenableexcept(int excepts) {
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// limit to what we know
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excepts &= FE_ALL_EXCEPT;
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#ifdef __x86_64__
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#ifndef NOX87
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// configure 8087 fpu control word
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// celaring the bits disables suppression
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unsigned short x87cw;
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asm("fstcw\t%0" : "=m"(x87cw));
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x87cw &= ~excepts;
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asm("fldcw\t%0" : /* no inputs */ : "m"(x87cw));
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#endif
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// configure modern sse control word
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// clearing the bits disables suppression
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unsigned mxcsr;
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asm("stmxcsr\t%0" : "=m"(mxcsr));
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mxcsr &= ~(excepts << 7);
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asm("ldmxcsr\t%0" : /* no inputs */ : "m"(mxcsr));
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return 0;
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#elif defined(__aarch64__)
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unsigned fpcr = __builtin_aarch64_get_fpcr();
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unsigned want = excepts << 8;
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unsigned fpcr2 = fpcr | want;
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if (fpcr != fpcr2) {
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__builtin_aarch64_set_fpcr(fpcr2);
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fpcr2 = __builtin_aarch64_get_fpsr();
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if ((fpcr2 & want) != want)
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return -1; // not supported by cpu
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}
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return (fpcr >> 8) & FE_ALL_EXCEPT;
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#else
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return -1;
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#endif
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}
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