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Diffstat (limited to 'src/VBox/Runtime/common/math/log2.asm')
| -rw-r--r-- | src/VBox/Runtime/common/math/log2.asm | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/src/VBox/Runtime/common/math/log2.asm b/src/VBox/Runtime/common/math/log2.asm new file mode 100644 index 00000000..13f4f85f --- /dev/null +++ b/src/VBox/Runtime/common/math/log2.asm @@ -0,0 +1,229 @@ +; $Id: log2.asm $ +;; @file +; IPRT - No-CRT log2 - AMD64 & X86. +; + +; +; Copyright (C) 2006-2022 Oracle and/or its affiliates. +; +; This file is part of VirtualBox base platform packages, as +; available from https://www.virtualbox.org. +; +; This program is free software; you can redistribute it and/or +; modify it under the terms of the GNU General Public License +; as published by the Free Software Foundation, in version 3 of the +; License. +; +; This program 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 +; General Public License for more details. +; +; You should have received a copy of the GNU General Public License +; along with this program; if not, see <https://www.gnu.org/licenses>. +; +; The contents of this file may alternatively be used under the terms +; of the Common Development and Distribution License Version 1.0 +; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included +; in the VirtualBox distribution, in which case the provisions of the +; CDDL are applicable instead of those of the GPL. +; +; You may elect to license modified versions of this file under the +; terms and conditions of either the GPL or the CDDL or both. +; +; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0 +; + + +%define RT_ASM_WITH_SEH64 +%include "iprt/asmdefs.mac" +%include "iprt/x86.mac" + + +BEGINCODE + +extern NAME(RT_NOCRT(feraiseexcept)) + +;; +; Compute the log2 of rd +; @returns st(0) / xmm0 +; @param rd [xSP + xCB*2] / xmm0 +RT_NOCRT_BEGINPROC log2 + push xBP + SEH64_PUSH_xBP + mov xBP, xSP + SEH64_SET_FRAME_xBP 0 + sub xSP, 20h + SEH64_ALLOCATE_STACK 20h + SEH64_END_PROLOGUE + + ; + ; Load the input into st0. + ; +%ifdef RT_ARCH_AMD64 + movsd [xBP - 10h], xmm0 + fld qword [xBP - 10h] +%else + fld qword [xBP + xCB*2] +%endif + + ; + ; Weed out non-normal values. + ; + fxam + fnstsw ax + mov cx, ax + and ax, X86_FSW_C3 | X86_FSW_C2 | X86_FSW_C0 + cmp ax, X86_FSW_C2 ; Normal finite number (excluding zero) + je .finite + cmp ax, X86_FSW_C3 ; Zero + je .zero + cmp ax, X86_FSW_C3 | X86_FSW_C2 ; Denormals + je .finite + cmp ax, X86_FSW_C0 | X86_FSW_C2 ; Infinity. + je .inf + jmp .nan + +.finite: + ; Negative number? + test cx, X86_FSW_C1 + jnz .negative + + ; Is it +1.0? + fld1 + fcomip st1 + jz .plus_one + + ; + ; The fyl2xp1 instruction (ST1=ST1*log2(ST0+1.0), popping ST0) has a + ; valid ST0 range of 1(1-sqrt(0.5)) (approx 0.29289321881) on both + ; sides of zero. We try use it if we can. + ; +.above_one: + ; For both fyl2xp1 and fyl2xp1 we need st1=1.0. + fld1 + fxch st0, st1 ; -> st0=input; st1=1.0 + + ; Check if the input is within the fyl2xp1 range. + fld qword [.s_r64AbsFyL2xP1InputMax xWrtRIP] + fcomip st0, st1 + jbe .cannot_use_fyl2xp1 + + fld qword [.s_r64AbsFyL2xP1InputMin xWrtRIP] + fcomip st0, st1 + jae .cannot_use_fyl2xp1 + + ; Do the calculation. +.use_fyl2xp1: + fsub st0, st1 ; -> st0=input-1; st1=1.0 + fyl2xp1 ; -> st0=1.0*log2(st0+1.0) + jmp .return_val + +.cannot_use_fyl2xp1: + fyl2x ; -> st0=1.0*log2(st0) + + ; + ; Return st0. + ; +.return_val: +%ifdef RT_ARCH_AMD64 + fstp qword [xBP - 10h] + movsd xmm0, [xBP - 10h] +%endif +.return: + leave + ret + + + ; + ; +1.0: Return +0.0. + ; +.plus_one: + ffreep st0 + fldz + jmp .return_val + + ; + ; Negative numbers: Return NaN and raise invalid operation. + ; +.negative: +.minus_inf: + ; Raise invalid operation +%ifdef RT_ARCH_X86 + mov dword [xSP], X86_FSW_IE +%elifdef ASM_CALL64_GCC + mov edi, X86_FSW_IE +%elifdef ASM_CALL64_MSC + mov ecx, X86_FSW_IE +%else + %error calling conv. +%endif + call NAME(RT_NOCRT(feraiseexcept)) + + ; Load NaN +%ifdef RT_ARCH_AMD64 + movsd xmm0, [.s_r64NaN xWrtRIP] +%else + fld qword [.s_r64NaN xWrtRIP] +%endif + jmp .return + + ; + ; +/-0.0: Return inf and raise divide by zero error. + ; +.zero: + ffreep st0 + + ; Raise div/0 +%ifdef RT_ARCH_X86 + mov dword [xSP], X86_FSW_ZE +%elifdef ASM_CALL64_GCC + mov edi, X86_FSW_ZE +%elifdef ASM_CALL64_MSC + mov ecx, X86_FSW_ZE +%else + %error calling conv. +%endif + call NAME(RT_NOCRT(feraiseexcept)) + + ; Load +Inf +%ifdef RT_ARCH_AMD64 + movsd xmm0, [.s_r64MinusInf xWrtRIP] +%else + fld qword [.s_r64MinusInf xWrtRIP] +%endif + jmp .return + + ; + ; -Inf: Same as other negative numbers + ; +Inf: return +Inf. Join path with NaN. + ; +.inf: + test cx, X86_FSW_C1 ; sign bit + jnz .minus_inf + + ; + ; NaN: Return the input NaN value as is, if we can. + ; +.nan: +%ifdef RT_ARCH_AMD64 + ffreep st0 +%endif + jmp .return + +ALIGNCODE(8) + ;; The fyl2xp1 instruction only works between +/-1(1-sqrt(0.5)). + ; These two variables is that range + 1.0, so we can compare directly + ; with the input w/o any extra fsub and fabs work. +.s_r64AbsFyL2xP1InputMin: + dq 0.708 ; -0.292 + 1.0 +.s_r64AbsFyL2xP1InputMax: + dq 1.292 +;.s_r64AbsFyL2xP1Range: +; dq 0.292 +.s_r64MinusInf: + dq RTFLOAT64U_INF_MINUS +.s_r64NaN: + dq RTFLOAT64U_QNAN_MINUS +ENDPROC RT_NOCRT(log2) + |