User Guide

138 128-Bit Media and Scientific Programming
AMD64 Technology 24592—Rev. 3.15—November 2009
be unaligned. Figure 4-18 shows the MASKMOVDQU operation. It is useful for the handling of end
cases in block copies and block fills based on streaming stores.
Figure 4-18. MASKMOVDQU Move Mask Operation
Move Mask.
• PMOVMSKB—Packed Move Mask Byte
The PMOVMSKB instruction moves the most-significant bit of each byte in an XMM register to the
low-order word of a 32-bit or 64-bit general-purpose register, with zero-extension. The instruction is
useful for extracting bits from mask patterns, or zero values from quantized data, or sign bits—
resulting in a byte that can be used for data-dependent branching. Figure 4-19 on page 139 shows the
PMOVMSKB operation.
operand 1
. . . . . . . . . . . . . .
. . . . . . . . . . . . . .
127 0
operand 2
127 0
select
select
store address
memory
rDI
513-148.eps