Description:
MSKxL and MSKxH set selected bytes of register Ra to zero, storing the result in register Rc. Register Rbv’<2:0> selects the starting position of the field of zero bytes, and the function code selects the maximum width: 1, 2, 4, or 8 bytes. The instructions generate a byte, word, longword, or quadword field of zeros that can spread across two registers at an arbitrary byte alignment.
Notes:
The comments in the examples below assume that the effective address (ea) of X(R11) is such that (ea mod 8) = 5, the value of the aligned quadword containing X(R11) is CBAx xxxx, the value of the aligned quadword containing X+7(R11) is yyyH GFED, the value to be stored from R5 is HGFE DCBA, and the datum is
The examples below are the most general case; if more information is known about the value or intended alignment of X, shorter sequences can be used.
The intended sequence for storing an unaligned quadword R5 at address X(R11) is:
LDA | R6, X(R11) | ; R6<2:0> = (X mod 8) = 5 | |||
LDQ_U | R2, X+7(R11) | ; Ignores va<2:0>, R2 = yyyH GFED | |||
LDQ_U | R1, X(R11) | ; Ignores va<2:0>, R1 = CBAx xxxx | |||
INSQH | R5, R6, R4 | ; R4 = | 000H | GFED | |
INSQL | R5, R6, R3 | ; R3 = | CBA0 0000 | ||
MSKQH | R2, R6, R2 | ; R2 | = | yyy0 0000 | |
MSKQL | R1, R6, R1 | ; R1 | = | 000x xxxx | |
OR | R2, R4, R2 | ; R2 | = | yyyH GFED | |
OR | R1, R3, R1 | ; R1 | = | CBAx xxxx | |
STQ_U | R2, X+7(R11) | ; Must store high then low for | |||
STQ_U | R1, X(R11) | ; degenerate case of aligned QW | |||
The intended sequence for storing an unaligned longword R5 at X is:
LDA | R6, X(R11) | ; R6<2:0> = (X mod 8) = 5 | |||
LDQ_U | R2, X+3(R11) | ; Ignores va<2:0>, R2 = yyyy yyyD | |||
LDQ_U | R1, X(R11) | ; Ignores va<2:0>, R1 = CBAx xxxx | |||
INSLH | R5, R6, R4 | ; R4 = | 0000 | 000D | |
INSLL | R5, R6, R3 | ; R3 = | CBA0 0000 | ||
MSKLH | R2, R6, R2 | ; R2 | = | yyyy yyy0 | |
MSKLL | R1, R6, R1 | ; R1 | = | 000x xxxx | |
OR | R2, R4, R2 | ; R2 | = | yyyy yyyD | |
OR | R1, R3, R1 | ; R1 | = | CBAx xxxx | |
STQ_U | R2, X+3(R11) | ; Must store high then low for | |||
STQ_U | R1, X(R11) | ; degenerate case of aligned | |||
