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| en:multiasm:paarm:chapter_5_6 [2025/12/03 23:41] – [Data copy/move instructions] eriks.klavins | en:multiasm:paarm:chapter_5_6 [2026/02/27 16:23] (current) – jtokarz |
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| <fc #800000>''ADD''</fc> <fc #008000>''X3''</fc>, <fc #008000>''X4''</fc>, <fc #008000>''W5''</fc>, <fc #cd5c5c>''UXTW''</fc> <fc #6495ed>''@X3 = X4 + W5''</fc> | <fc #800000>''ADD''</fc> <fc #008000>''X3''</fc>, <fc #008000>''X4''</fc>, <fc #008000>''W5''</fc>, <fc #cd5c5c>''UXTW''</fc> <fc #6495ed>''@X3 = X4 + W5''</fc> |
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| {{:en:multiasm:paarm:addextended_1.jpg|}} | {{ :en:multiasm:paarm:addextended_1.jpg?600 |The ADD instruction with extended registers}} |
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| <fc #800000>''ADDS''</fc> <fc #008000>''X3''</fc>, <fc #008000>''X4''</fc>, <fc #008000>''W5''</fc>, <fc #cd5c5c>''UXTW''</fc> <fc #6495ed>''@X3 = X4 + W5 and update the status flags''</fc> | <fc #800000>''ADDS''</fc> <fc #008000>''X3''</fc>, <fc #008000>''X4''</fc>, <fc #008000>''W5''</fc>, <fc #cd5c5c>''UXTW''</fc> <fc #6495ed>''@X3 = X4 + W5 and update the status flags''</fc> |
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| {{:en:multiasm:paarm:addsextended_1.jpg|}} | {{ :en:multiasm:paarm:addsextended_1.jpg?600 |The ADDS instruction with extended registers}} |
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| The machine code representation of the assembler instruction would be like: | The machine code representation of the assembler instruction would be like: |
| In machine code, it is possible to determine the maximum value that can be added to a register. The ‘imm12’ bits limit the value to 0-4095. Besides that, the ‘sh’ bit allows to shift left (LSL) the immediate value by 12 bits. | In machine code, it is possible to determine the maximum value that can be added to a register. The ‘imm12’ bits limit the value to 0-4095. Besides that, the ‘sh’ bit allows to shift left (LSL) the immediate value by 12 bits. |
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| {{:en:multiasm:paarm:addimediate.jpg|}} | {{ :en:multiasm:paarm:addimediate.jpg?600 |The ADDS (ADD) instructions with immediate value}} |
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| Examples with immediate the <fc #800000>''ADD''</fc> instruction | Examples with immediate the <fc #800000>''ADD''</fc> instruction |
| The final add instruction type adds two registers together, with one register shifted; the shift can be LSL (Logical Shift Left), LSR (Logical Shift Right), or ASR (Arithmetic Shift Right). The fourth shift option is not available. The number of bits in the ‘imm6’ field identifies the number of bits to be shifted for the ‘Rm’ register before it is added to the ‘Rn’ register. | The final add instruction type adds two registers together, with one register shifted; the shift can be LSL (Logical Shift Left), LSR (Logical Shift Right), or ASR (Arithmetic Shift Right). The fourth shift option is not available. The number of bits in the ‘imm6’ field identifies the number of bits to be shifted for the ‘Rm’ register before it is added to the ‘Rn’ register. |
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| {{:en:multiasm:paarm:addshifted.jpg|}} | {{ :en:multiasm:paarm:addshifted.jpg?600 |The ADDS (ADD) instruction with a shifted register}} |
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| Similar options are available for many other ARMv8 instructions. The instruction set documentation may provide the necessary information to determine the possibilities and restrictions on instruction usage. By examining the instruction's binary form, it is possible to identify its capabilities and limitations. Assembler code is converted to binary, and the final binary code for the instruction depends on the provided operands and, if available, options. | Similar options are available for many other ARMv8 instructions. The instruction set documentation may provide the necessary information to determine the possibilities and restrictions on instruction usage. By examining the instruction's binary form, it is possible to identify its capabilities and limitations. Assembler code is converted to binary, and the final binary code for the instruction depends on the provided operands and, if available, options. |
| ''<fc #800000>NEG</fc> <fc #008000>X24</fc>, <fc #008000>X25</fc> <fc #6495ed>@ logical NOT, X24 is set to inverted X25</fc>'' | ''<fc #800000>NEG</fc> <fc #008000>X24</fc>, <fc #008000>X25</fc> <fc #6495ed>@ logical NOT, X24 is set to inverted X25</fc>'' |
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| Remember that most instructions, which operate with registers, can update the status register by adding the postfix S at the end of the instruction. Logical instructions are fundamental for low-level programming. These instructions allow taking control over bits and are widely used in system code, device drivers, and embedded systems. | Remember that most instructions, which operate with registers, can update the status register by adding the postfix S at the end of the instruction. Logical instructions are fundamental for low-level programming. These instructions allow taking control over bits and are widely used in system code, device drivers, and embedded systems. Some instructions can perform combined bitwise operations, like ''<fc #800000>ORN</fc>'', which performs an OR operation with the inverted second operand. |
