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113 lines
3.1 KiB
ArmAsm
113 lines
3.1 KiB
ArmAsm
/* ix87 specific implementation of exp(x)-1.
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Copyright (C) 1996-2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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<https://www.gnu.org/licenses/>. */
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/* Using: e^x - 1 = 2^(x * log2(e)) - 1 */
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#include <sysdep.h>
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#include <machine/asm.h>
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#include <i386-math-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 minus1,@object
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minus1: .double -1.0
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ASM_SIZE_DIRECTIVE(minus1)
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.type one,@object
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one: .double 1.0
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ASM_SIZE_DIRECTIVE(one)
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.type l2e,@object
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l2e: .quad 0xb8aa3b295c17f0bc /* 1.442695040888963407359924681002 */
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.short 0x3fff
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ASM_SIZE_DIRECTIVE(l2e)
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DEFINE_FLT_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(__expm1f)
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movzwl 4+2(%esp), %eax
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xorb $0x80, %ah // invert sign bit (now 1 is "positive")
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cmpl $0xc2b1, %eax // is num >= 88.5?
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jae HIDDEN_JUMPTARGET (__expf)
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flds 4(%esp) // x
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fxam // Is NaN, +-Inf or +-0?
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xorb $0x80, %ah
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cmpl $0xc190, %eax // is num <= -18.0?
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fstsw %ax
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movb $0x45, %ch
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jb 4f
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// Below -18.0 (may be -NaN or -Inf).
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andb %ah, %ch
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#ifdef PIC
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LOAD_PIC_REG (dx)
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#endif
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cmpb $0x01, %ch
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je 5f // If -NaN, jump.
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jmp 2f // -large, possibly -Inf.
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4: // In range -18.0 to 88.5 (may be +-0 but not NaN or +-Inf).
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andb %ah, %ch
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cmpb $0x40, %ch
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je 3f // If +-0, jump.
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#ifdef PIC
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LOAD_PIC_REG (dx)
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#endif
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5: fldt MO(l2e) // log2(e) : x
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fmulp // log2(e)*x
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fld %st // log2(e)*x : log2(e)*x
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// Set round-to-nearest temporarily.
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subl $8, %esp
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cfi_adjust_cfa_offset (8)
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fstcw 4(%esp)
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movl $0xf3ff, %ecx
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andl 4(%esp), %ecx
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movl %ecx, (%esp)
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fldcw (%esp)
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frndint // int(log2(e)*x) : log2(e)*x
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fldcw 4(%esp)
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addl $8, %esp
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cfi_adjust_cfa_offset (-8)
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fsubr %st, %st(1) // int(log2(e)*x) : fract(log2(e)*x)
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fxch // fract(log2(e)*x) : int(log2(e)*x)
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f2xm1 // 2^fract(log2(e)*x)-1 : int(log2(e)*x)
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fscale // 2^(log2(e)*x)-2^int(log2(e)*x) : int(log2(e)*x)
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fxch // int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
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fldl MO(one) // 1 : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
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fscale // 2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
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fsubrl MO(one) // 1-2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
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fstp %st(1) // 1-2^int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
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fsubrp %st, %st(1) // 2^(log2(e)*x)
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FLT_CHECK_FORCE_UFLOW
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ret
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2: fstp %st
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fldl MO(minus1) // Set result to -1.0.
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3: ret
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END(__expm1f)
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libm_alias_float (__expm1, expm1)
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