| Format | Assembly Format | Description |
|---|---|---|
| FE 12 <unsigned int8> | unaligned. alignment |
Subsequent pointer instruction might be unaligned. |
…, addr → …, addr
The unaligned. prefix specifies that addr (an unmanaged pointer (&), or native int) on the stack might not be aligned to the natural size of the immediately following ldind, stind, ldfld, stfld, ldobj, stobj, initblk, or cpblk instruction. That is, for a ldind.i4 instruction the alignment of addr might not be to a 4-byte boundary. For initblk and cpblk the default alignment is architecture-dependent (4-byte on 32-bit CPUs, 8-byte on 64-bit CPUs). Code generators that do not restrict their output to a 32-bit word size (see Partition I and Partition II) shall use unaligned. if the alignment is not known at compile time to be 8-byte.
The value of alignment shall be 1, 2, or 4 and means that the generated code should assume that addr is byte, double-byte, or quad-byte-aligned, respectively.
[Rationale: While the alignment for a cpblk instruction would logically require two numbers (one for the source and one for the destination), there is no noticeable impact on performance if only the lower number is specified. end rationale]
The unaligned. and volatile. prefixes can be combined in either order. They shall immediately precede a ldind, stind, ldfld, stfld, ldobj, stobj, initblk, or cpblk instruction.
[Note: See Partition I, 12.7 for information about atomicity and data alignment. end note]
None.
An unaligned. prefix shall be followed immediately by one of the instructions listed above.