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+/* ix87 specific implementation of pow function.
+ Copyright (C) 1996, 1997 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+#include <machine/asm.h>
+
+#ifdef __ELF__
+ .section .rodata
+#else
+ .text
+#endif
+
+ .align ALIGNARG(4)
+ ASM_TYPE_DIRECTIVE(infinity,@object)
+inf_zero:
+infinity:
+ .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
+ ASM_SIZE_DIRECTIVE(infinity)
+ ASM_TYPE_DIRECTIVE(zero,@object)
+zero: .double 0.0
+ ASM_SIZE_DIRECTIVE(zero)
+ ASM_TYPE_DIRECTIVE(minf_mzero,@object)
+minf_mzero:
+minfinity:
+ .byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
+mzero:
+ .byte 0, 0, 0, 0, 0, 0, 0, 0x80
+ ASM_SIZE_DIRECTIVE(minf_mzero)
+ ASM_TYPE_DIRECTIVE(one,@object)
+one: .double 1.0
+ ASM_SIZE_DIRECTIVE(one)
+ ASM_TYPE_DIRECTIVE(limit,@object)
+limit: .double 0.29
+ ASM_SIZE_DIRECTIVE(limit)
+
+#ifdef PIC
+#define MO(op) op##@GOTOFF(%ecx)
+#define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
+#else
+#define MO(op) op
+#define MOX(op,x,f) op(,x,f)
+#endif
+
+ .text
+ENTRY(__ieee754_powf)
+ flds 8(%esp) // y
+ fxam
+
+#ifdef PIC
+ call 1f
+1: popl %ecx
+ addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx
+#endif
+
+ fnstsw
+ movb %ah, %dl
+ andb $0x45, %ah
+ cmpb $0x40, %ah // is y == 0 ?
+ je 11f
+
+ cmpb $0x05, %ah // is y == ±inf ?
+ je 12f
+
+ cmpb $0x01, %ah // is y == NaN ?
+ je 30f
+
+ flds 4(%esp) // x : y
+
+ subl $4, %esp
+
+ fxam
+ fnstsw
+ movb %ah, %dh
+ andb $0x45, %ah
+ cmpb $0x40, %ah
+ je 20f // x is ±0
+
+ cmpb $0x05, %ah
+ je 15f // x is ±inf
+
+ fxch // y : x
+
+ /* First see whether `y' is a natural number. In this case we
+ can use a more precise algorithm. */
+ fld %st // y : y : x
+ fistpl (%esp) // y : x
+ fildl (%esp) // int(y) : y : x
+ fucomp %st(1) // y : x
+ fnstsw
+ sahf
+ jne 2f
+
+ /* OK, we have an integer value for y. */
+ popl %edx
+ orl $0, %edx
+ fstp %st(0) // x
+ jns 4f // y >= 0, jump
+ fdivrl MO(one) // 1/x (now referred to as x)
+ negl %edx
+4: fldl MO(one) // 1 : x
+ fxch
+
+6: shrl $1, %edx
+ jnc 5f
+ fxch
+ fmul %st(1) // x : ST*x
+ fxch
+5: fmul %st(0), %st // x*x : ST*x
+ testl %edx, %edx
+ jnz 6b
+ fstp %st(0) // ST*x
+30: ret
+
+ .align ALIGNARG(4)
+2: /* y is a real number. */
+ fxch // x : y
+ fldl MO(one) // 1.0 : x : y
+ fld %st(1) // x : 1.0 : x : y
+ fsub %st(1) // x-1 : 1.0 : x : y
+ fabs // |x-1| : 1.0 : x : y
+ fcompl MO(limit) // 1.0 : x : y
+ fnstsw
+ fxch // x : 1.0 : y
+ sahf
+ ja 7f
+ fsub %st(1) // x-1 : 1.0 : y
+ fyl2xp1 // log2(x) : y
+ jmp 8f
+
+7: fyl2x // log2(x) : y
+8: fmul %st(1) // y*log2(x) : y
+ fst %st(1) // y*log2(x) : y*log2(x)
+ frndint // int(y*log2(x)) : y*log2(x)
+ fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x))
+ fxch // fract(y*log2(x)) : int(y*log2(x))
+ f2xm1 // 2^fract(y*log2(x))-1 : int(y*log2(x))
+ faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x))
+ fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
+ addl $4, %esp
+ fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
+ ret
+
+
+ // pow(x,±0) = 1
+ .align ALIGNARG(4)
+11: fstp %st(0) // pop y
+ fldl MO(one)
+ ret
+
+ // y == ±inf
+ .align ALIGNARG(4)
+12: fstp %st(0) // pop y
+ flds 4(%esp) // x
+ fabs
+ fcompl MO(one) // < 1, == 1, or > 1
+ fnstsw
+ andb $0x45, %ah
+ cmpb $0x45, %ah
+ je 13f // jump if x is NaN
+
+ cmpb $0x40, %ah
+ je 14f // jump if |x| == 1
+
+ shlb $1, %ah
+ xorb %ah, %dl
+ andl $2, %edx
+ fldl MOX(inf_zero, %edx, 4)
+ ret
+
+ .align ALIGNARG(4)
+14: fldl MO(infinity)
+ fmull MO(zero) // raise invalid exception
+ ret
+
+ .align ALIGNARG(4)
+13: flds 4(%esp) // load x == NaN
+ ret
+
+ .align ALIGNARG(4)
+ // x is ±inf
+15: fstp %st(0) // y
+ testb $2, %dh
+ jz 16f // jump if x == +inf
+
+ // We must find out whether y is an odd integer.
+ fld %st // y : y
+ fistpl (%esp) // y
+ fildl (%esp) // int(y) : y
+ fucompp // <empty>
+ fnstsw
+ sahf
+ jne 17f
+
+ // OK, the value is an integer, but is the number of bits small
+ // enough so that all are coming from the mantissa?
+ popl %edx
+ testb $1, %dl
+ jz 18f // jump if not odd
+ movl %edx, %eax
+ orl %edx, %edx
+ jns 155f
+ negl %eax
+155: cmpl $0x01000000, %eax
+ ja 18f // does not fit in mantissa bits
+ // It's an odd integer.
+ shrl $31, %edx
+ fldl MOX(minf_mzero, %edx, 8)
+ ret
+
+ .align ALIGNARG(4)
+16: fcompl MO(zero)
+ addl $4, %esp
+ fnstsw
+ shrl $5, %eax
+ andl $8, %eax
+ fldl MOX(inf_zero, %eax, 1)
+ ret
+
+ .align ALIGNARG(4)
+17: shll $30, %edx // sign bit for y in right position
+ addl $4, %esp
+18: shrl $31, %edx
+ fldl MOX(inf_zero, %edx, 8)
+ ret
+
+ .align ALIGNARG(4)
+ // x is ±0
+20: fstp %st(0) // y
+ testb $2, %dl
+ jz 21f // y > 0
+
+ // x is ±0 and y is < 0. We must find out whether y is an odd integer.
+ testb $2, %dh
+ jz 25f
+
+ fld %st // y : y
+ fistpl (%esp) // y
+ fildl (%esp) // int(y) : y
+ fucompp // <empty>
+ fnstsw
+ sahf
+ jne 26f
+
+ // OK, the value is an integer, but is the number of bits small
+ // enough so that all are coming from the mantissa?
+ popl %edx
+ testb $1, %dl
+ jz 27f // jump if not odd
+ cmpl $0xff000000, %edx
+ jbe 27f // does not fit in mantissa bits
+ // It's an odd integer.
+ // Raise divide-by-zero exception and get minus infinity value.
+ fldl MO(one)
+ fdivl MO(zero)
+ fchs
+ ret
+
+25: fstp %st(0)
+26: popl %eax
+27: // Raise divide-by-zero exception and get infinity value.
+ fldl MO(one)
+ fdivl MO(zero)
+ ret
+
+ .align ALIGNARG(4)
+ // x is ±0 and y is > 0. We must find out whether y is an odd integer.
+21: testb $2, %dh
+ jz 22f
+
+ fld %st // y : y
+ fistpl (%esp) // y
+ fildl (%esp) // int(y) : y
+ fucompp // <empty>
+ fnstsw
+ sahf
+ jne 23f
+
+ // OK, the value is an integer, but is the number of bits small
+ // enough so that all are coming from the mantissa?
+ popl %edx
+ testb $1, %dl
+ jz 24f // jump if not odd
+ cmpl $0xff000000, %edx
+ jae 24f // does not fit in mantissa bits
+ // It's an odd integer.
+ fldl MO(mzero)
+ ret
+
+22: fstp %st(0)
+23: popl %eax
+24: fldl MO(zero)
+ ret
+
+END(__ieee754_powf)