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179 lines
4.3 KiB
ArmAsm
179 lines
4.3 KiB
ArmAsm
/* Compute cubic root of float value.
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Copyright (C) 1997-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Dirk Alboth <dirka@uni-paderborn.de> and
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Ulrich Drepper <drepper@cygnus.com>, 1997.
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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 <machine/asm.h>
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#include <libm-alias-float.h>
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.section .rodata
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.align ALIGNARG(4)
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.type f3,@object
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f3: .double 0.191502161678719066
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ASM_SIZE_DIRECTIVE(f3)
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.type f2,@object
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f2: .double 0.697570460207922770
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ASM_SIZE_DIRECTIVE(f2)
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.type f1,@object
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f1: .double 0.492659620528969547
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ASM_SIZE_DIRECTIVE(f1)
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#define CBRT2 1.2599210498948731648
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#define ONE_CBRT2 0.793700525984099737355196796584
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#define SQR_CBRT2 1.5874010519681994748
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#define ONE_SQR_CBRT2 0.629960524947436582364439673883
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.type factor,@object
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.align ALIGNARG(4)
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factor: .double ONE_SQR_CBRT2
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.double ONE_CBRT2
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.double 1.0
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.double CBRT2
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.double SQR_CBRT2
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ASM_SIZE_DIRECTIVE(factor)
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.type two25,@object
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two25: .byte 0, 0, 0, 0x4c
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ASM_SIZE_DIRECTIVE(two25)
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#ifdef PIC
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#define MO(op) op##@GOTOFF(%ebx)
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#define MOX(op,x) op##@GOTOFF(%ebx,x,1)
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#else
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#define MO(op) op
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#define MOX(op,x) op(x)
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#endif
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.text
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ENTRY(__cbrtf)
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movl 4(%esp), %eax
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xorl %ecx, %ecx
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movl %eax, %edx
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andl $0x7fffffff, %eax
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jz 1f
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cmpl $0x7f800000, %eax
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jae 1f
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#ifdef PIC
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pushl %ebx
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cfi_adjust_cfa_offset (4)
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cfi_rel_offset (ebx, 0)
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LOAD_PIC_REG (bx)
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#endif
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cmpl $0x00800000, %eax
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jae 2f
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#ifdef PIC
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flds 8(%esp)
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#else
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flds 4(%esp)
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#endif
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fmuls MO(two25)
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movl $-25, %ecx
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#ifdef PIC
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fstps 8(%esp)
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movl 8(%esp), %eax
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#else
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fstps 4(%esp)
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movl 4(%esp), %eax
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#endif
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movl %eax, %edx
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andl $0x7fffffff, %eax
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2: shrl $23, %eax
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andl $0x807fffff, %edx
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subl $126, %eax
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orl $0x3f000000, %edx
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addl %eax, %ecx
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#ifdef PIC
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movl %edx, 8(%esp)
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flds 8(%esp) /* xm */
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#else
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movl %edx, 4(%esp)
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flds 4(%esp) /* xm */
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#endif
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fabs
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/* The following code has two tracks:
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a) compute the normalized cbrt value
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b) compute xe/3 and xe%3
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The right track computes the value for b) and this is done
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in an optimized way by avoiding division.
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But why two tracks at all? Very easy: efficiency. Some FP
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instruction can overlap with a certain amount of integer (and
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FP) instructions. So we get (except for the imull) all
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instructions for free. */
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fld %st(0) /* xm : xm */
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fmull MO(f3) /* f3*xm : xm */
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movl $1431655766, %eax
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fsubrl MO(f2) /* f2-f3*xm : xm */
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imull %ecx
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fmul %st(1) /* (f2-f3*xm)*xm : xm */
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movl %ecx, %eax
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faddl MO(f1) /* u:=f1+(f2-f3*xm)*xm : xm */
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sarl $31, %eax
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fld %st /* u : u : xm */
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subl %eax, %edx
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fmul %st(1) /* u*u : u : xm */
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fld %st(2) /* xm : u*u : u : xm */
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fadd %st /* 2*xm : u*u : u : xm */
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fxch %st(1) /* u*u : 2*xm : u : xm */
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fmul %st(2) /* t2:=u*u*u : 2*xm : u : xm */
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movl %edx, %eax
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fadd %st, %st(1) /* t2 : t2+2*xm : u : xm */
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leal (%edx,%edx,2),%edx
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fadd %st(0) /* 2*t2 : t2+2*xm : u : xm */
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subl %edx, %ecx
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faddp %st, %st(3) /* t2+2*xm : u : 2*t2+xm */
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shll $3, %ecx
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fmulp /* u*(t2+2*xm) : 2*t2+xm */
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fdivp %st, %st(1) /* u*(t2+2*xm)/(2*t2+xm) */
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fmull MOX(16+factor,%ecx) /* u*(t2+2*xm)/(2*t2+xm)*FACT */
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pushl %eax
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cfi_adjust_cfa_offset (4)
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fildl (%esp) /* xe/3 : u*(t2+2*xm)/(2*t2+xm)*FACT */
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fxch /* u*(t2+2*xm)/(2*t2+xm)*FACT : xe/3 */
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fscale /* u*(t2+2*xm)/(2*t2+xm)*FACT*2^xe/3 */
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popl %edx
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cfi_adjust_cfa_offset (-4)
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#ifdef PIC
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movl 8(%esp), %eax
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popl %ebx
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cfi_adjust_cfa_offset (-4)
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cfi_restore (ebx)
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#else
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movl 4(%esp), %eax
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#endif
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testl %eax, %eax
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fstp %st(1)
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jns 4f
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fchs
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4: ret
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/* Return the argument. */
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1: flds 4(%esp)
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ret
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END(__cbrtf)
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libm_alias_float (__cbrt, cbrt)
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