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Similar to various other bugs in this area, hypot functions can fail to raise the underflow exception when the result is tiny and inexact but one or more low bits of the intermediate result that is scaled down (or, in the i386 case, converted from a wider evaluation format) are zero. This patch forces the exception in a similar way to previous fixes. Note that this issue cannot arise for implementations of hypotf using double (or wider) for intermediate evaluation (if hypotf should underflow, that means the double square root is being computed of some number of the form N*2^-298, for 0 < N < 2^46, which is exactly represented as a double, and whatever the rounding mode such a square root cannot have a mantissa with all zeroes after the initial 23 bits). Thus no changes are made to hypotf implementations in this patch, only to hypot and hypotl. Tested for x86_64, x86, mips64 and powerpc. [BZ #18803] * sysdeps/i386/fpu/e_hypot.S: Use DEFINE_DBL_MIN. (MO): New macro. (__ieee754_hypot) [PIC]: Load PIC register. (__ieee754_hypot): Use DBL_NARROW_EVAL_UFLOW_NONNEG instead of DBL_NARROW_EVAL. * sysdeps/ieee754/dbl-64/e_hypot.c (__ieee754_hypot): Use math_check_force_underflow_nonneg in case where result might be tiny. * sysdeps/ieee754/ldbl-128/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/ieee754/ldbl-96/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/powerpc/fpu/e_hypot.c (__ieee754_hypot): Likewise. * math/auto-libm-test-in: Add more tests of hypot. * math/auto-libm-test-out: Regenerated.
76 lines
1.7 KiB
ArmAsm
76 lines
1.7 KiB
ArmAsm
/* Compute the hypothenuse of X and Y.
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Copyright (C) 1998-2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include <i386-math-asm.h>
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DEFINE_DBL_MIN
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#ifdef PIC
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# define MO(op) op##@GOTOFF(%edx)
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#else
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# define MO(op) op
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#endif
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.text
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ENTRY(__ieee754_hypot)
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#ifdef PIC
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LOAD_PIC_REG (dx)
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#endif
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fldl 4(%esp) // x
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fxam
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fnstsw
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fldl 12(%esp) // y : x
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movb %ah, %ch
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fxam
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fnstsw
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movb %ah, %al
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orb %ch, %ah
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sahf
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jc 1f
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fmul %st(0) // y * y : x
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fxch // x : y * y
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fmul %st(0) // x * x : y * y
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faddp // x * x + y * y
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fsqrt
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DBL_NARROW_EVAL_UFLOW_NONNEG
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2: ret
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// We have to test whether any of the parameters is Inf.
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// In this case the result is infinity.
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1: andb $0x45, %al
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cmpb $5, %al
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je 3f // jump if y is Inf
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andb $0x45, %ch
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cmpb $5, %ch
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jne 4f // jump if x is not Inf
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fxch
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3: fstp %st(1)
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fabs
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jmp 2b
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4: testb $1, %al
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jnz 5f // y is NaN
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fxch
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5: fstp %st(1)
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jmp 2b
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END(__ieee754_hypot)
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strong_alias (__ieee754_hypot, __hypot_finite)
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