49 lines
4.7 KiB
Markdown
Executable File
49 lines
4.7 KiB
Markdown
Executable File
# SUB — Subtract
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## Description
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Subtracts the second operand (source operand) from the first operand (destination operand) and stores the result in the destination operand.
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The destination operand can be a register or a memory location; the source operand can be an immediate, register, or memory location. However,
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two memory operands cannot be used in one instruction. When an immediate value is used as an operand, it is sign-extended to the length of the
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destination operand format.
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## Instruction
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| Opcode | Assembly | Op/En | Modern Mode | Legacy Mode | Description |
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|------------------|------------------|-------|-------------|-------------|--------------------------------------------------------------------|
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| 2C ib | SUB AL, imm8 | I | Valid | Valid | Subtract imm8 from AL. |
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| 2D iw | SUB AX, imm16 | I | Valid | Valid | Subtract imm16 from AX. |
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| 2D id | SUB EAX, imm32 | I | Valid | Valid | Subtract imm32 from EAX. |
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| REX.W + 2D id | SUB RAX, imm32 | I | Valid | N.E. | Subtract imm32 sign-extended to 64-bits from RAX. |
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| 80 /5 ib | SUB r/m8, imm8 | MI | Valid | Valid | Subtract imm8 from r/m8. |
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| REX + 80 /5 ib | SUB r/m8*, imm8 | MI | Valid | N.E. | Subtract imm8 from r/m8. |
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| 81 /5 iw | SUB r/m16, imm16 | MI | Valid | Valid | Subtract imm16 from r/m16. |
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| 81 /5 id | SUB r/m32, imm32 | MI | Valid | Valid | Subtract imm32 from r/m32. |
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| REX.W + 81 /5 id | SUB r/m64, imm32 | MI | Valid | N.E. | Subtract imm32 sign-extended to 64-bits from r/m64. |
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| 83 /5 ib | SUB r/m16, imm8 | MI | Valid | Valid | Subtract sign-extended imm8 from r/m16. |
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| 83 /5 ib | SUB r/m32, imm8 | MI | Valid | Valid | Subtract sign-extended imm8 from r/m32. |
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| REX.W + 83 /5 ib | SUB r/m64, imm8 | MI | Valid | N.E. | Subtract sign-extended imm8 from r/m64. |
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| 28 /r | SUB r/m8, r8 | MR | Valid | Valid | Subtract r8 from r/m8. |
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| REX + 28 /r | SUB r/m8*, r8* | MR | Valid | N.E. | Subtract r8 from r/m8. |
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| 29 /r | SUB r/m16, r16 | MR | Valid | Valid | Subtract r16 from r/m16. |
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| 29 /r | SUB r/m32, r32 | MR | Valid | Valid | Subtract r32 from r/m32. |
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| REX.W + 29 /r | SUB r/m64, r64 | MR | Valid | N.E. | Subtract r64 from r/m64. |
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| 2A /r | SUB r8, r/m8 | RM | Valid | Valid | Subtract r/m8 from r8. |
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| REX + 2A /r | SUB r8*, r/m8* | RM | Valid | N.E. | Subtract r/m8 from r8. |
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| 2B /r | SUB r16, r/m16 | RM | Valid | Valid | Subtract r/m16 from r16. |
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| 2B /r | SUB r32, r/m32 | RM | Valid | Valid | Subtract r/m32 from r32. |
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| REX.W + 2B /r | SUB r64, r/m64 | RM | Valid | N.E. | Subtract r/m64 from r64. |
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- In 64-bit mode, r/m8 can not be encoded to access the following byte registers if a REX prefix is used: AH, BH, CH, DH.
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## Information
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This instruction can be used with a LOCK prefix to allow the instruction to be executed atomically.
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The SUB instruction performs integer subtraction. It evaluates the result for both signed and unsigned integer operands and sets the OF and CF
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flags to indicate an overflow in the signed or unsigned result, respectively. The SF flag indicates the sign of the signed result.
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In 64-bit mode, the instruction's default operation size is 32 bits. Using a REX prefix in the form of REX.R permits access to additional
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registers (R8-R15). Using a REX prefix in the form of REX.W promotes operation to 64 bits. See the summary chart at the beginning of this
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section for encoding data and limits.
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