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This allows direct inlining and hides away some assembly and bit-fiddling when manipulating the floating point environment. This only implements the x87/SSE versions, as of now.
125 lines
2.9 KiB
C++
125 lines
2.9 KiB
C++
/*
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* Copyright (c) 2022, Leon Albrecht <leon.a@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Types.h>
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// FIXME: Add equivalent datastructures for aarch64
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VALIDATE_IS_X86();
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namespace AK {
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enum class RoundingMode : u8 {
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NEAREST = 0b00,
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DOWN = 0b01,
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UP = 0b10,
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TRUNC = 0b11
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};
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union X87ControlWord {
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u16 cw;
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struct {
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u16 mask_invalid : 1; // IM
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u16 mask_denorm : 1; // DM
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u16 mask_zero_div : 1; // ZM
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u16 mask_overflow : 1; // OM
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u16 mask_underflow : 1; // UM
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u16 mask_precision : 1; // PM
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u16 : 2; // unused
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u16 precision : 2; // PC
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RoundingMode rounding_control : 2; // RC
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u16 infinity_control : 1; // X
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u16 : 3; // unused
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};
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};
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static_assert(sizeof(X87ControlWord) == sizeof(u16));
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union MXCSR {
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u32 mxcsr;
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struct {
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u32 invalid_operation_flag : 1; // IE
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u32 denormal_operation_flag : 1; // DE
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u32 divide_by_zero_flag : 1; // ZE
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u32 overflow_flag : 1; // OE
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u32 underflow_flag : 1; // UE
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u32 precision_flag : 1; // PE
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u32 denormals_are_zero : 1; // DAZ
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u32 invalid_operation_mask : 1; // IM
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u32 denormal_operation_mask : 1; // DM
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u32 divide_by_zero_mask : 1; // ZM
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u32 overflow_mask : 1; // OM
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u32 underflow_mask : 1; // UM
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u32 precision_mask : 1; // PM
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RoundingMode rounding_control : 2; // RC
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u32 flush_to_zero : 1; // FTZ
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u32 __reserved : 16;
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};
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};
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static_assert(sizeof(MXCSR) == sizeof(u32));
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ALWAYS_INLINE X87ControlWord get_cw_x87()
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{
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X87ControlWord control_word;
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asm("fnstcw %0"
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: "=m"(control_word));
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return control_word;
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}
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ALWAYS_INLINE void set_cw_x87(X87ControlWord control_word)
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{
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asm("fldcw %0" ::"m"(control_word));
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}
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ALWAYS_INLINE MXCSR get_mxcsr()
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{
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MXCSR mxcsr;
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asm("stmxcsr %0"
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: "=m"(mxcsr));
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return mxcsr;
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}
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ALWAYS_INLINE void set_mxcsr(MXCSR mxcsr)
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{
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asm("ldmxcsr %0" ::"m"(mxcsr));
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}
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class X87RoundingModeScope {
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public:
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X87RoundingModeScope(RoundingMode rounding_mode)
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{
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m_cw = get_cw_x87();
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auto cw = m_cw;
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cw.rounding_control = rounding_mode;
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set_cw_x87(cw);
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}
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~X87RoundingModeScope()
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{
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set_cw_x87(m_cw);
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}
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private:
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X87ControlWord m_cw;
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};
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class SSERoundingModeScope {
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public:
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SSERoundingModeScope(RoundingMode rounding_mode)
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{
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m_mxcsr = get_mxcsr();
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auto mxcsr = m_mxcsr;
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mxcsr.rounding_control = rounding_mode;
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set_mxcsr(mxcsr);
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}
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~SSERoundingModeScope()
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{
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set_mxcsr(m_mxcsr);
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}
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private:
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MXCSR m_mxcsr;
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};
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}
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