Semiconductor & Computer Engineering
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Editing immediate value
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| − | + | An '''immediate value''' (or simply an '''immediate''' or '''imm''') is a piece of data that is stored as part of the instruction itself instead of being in a [[memory]] location or a [[register]]. Immediate values are typically used in instructions that [[Load/Store instruction|load]] a value or performs an [[arithmetic instruction|arithmetic]] or a [[logic instruction|logical]] operation on a constant. | |
| − | An '''immediate value''' (or simply an '''immediate''' or '''imm''') is a piece of data that is stored as part of the instruction itself instead of being in a [[memory]] location or a [[register]]. Immediate values are typically used in instructions that [[Load/Store instruction|load]] a value or performs an [[arithmetic instruction|arithmetic]] or a [[logic instruction|logical]] operation on a | ||
== Overview == | == Overview == | ||
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The instruction set may also support the common case of adding a constant value (such as in the case of many programming languages that support [[pre-increment operator|++var]]). | The instruction set may also support the common case of adding a constant value (such as in the case of many programming languages that support [[pre-increment operator|++var]]). | ||
| − | <pre> | + | <pre>add r1, r1, 1 ; r1 = r1 + 1</pre> |
In the code above, the value <code>1</code> is an immediate value that gets encoded in the <code>add</code> instruction itself. | In the code above, the value <code>1</code> is an immediate value that gets encoded in the <code>add</code> instruction itself. | ||
== Implementation restrictions == | == Implementation restrictions == | ||
| − | + | Because the immediate value is packed into the instruction itself certain [[ISA]]s have a restricted range of values that can be used as an immediate value. For example in [[MIPS32]], an immediate value is limited to 16-bits. On some more complex architectures such as [[ARM]], some instructions may accept a 16-bit value, others might accepted a smaller range with a the ability to rate the bits as desired. | |
| − | Because the immediate value is packed into the instruction itself certain [[ISA]]s have a restricted range of values that can be used as an immediate value. For example in [[MIPS32]], an immediate value is limited to 16-bits. On some more complex architectures such as [[ARM]], some instructions may accept a 16-bit value, others might accepted a smaller range with a the ability to | ||
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[[Category:microprocessor architecture]] | [[Category:microprocessor architecture]] | ||
[[Category:Instruction set architecture]] | [[Category:Instruction set architecture]] | ||