HLASM Language Reference

CNOP Instruction
CNOP Instruction
The CNOP instruction aligns any instruction or other data on a specific halfword
boundary. This ensures an unbroken flow of executable instructions, since the
CNOP instruction generates no-operation instructions to fill the bytes skipped to
achieve specified alignment. If a control section has not been established, CNOP
will initiate an unnamed (private) control section.
►►──┬────────┬──CNOP──byte,boundary────────────────────────────────►◄
└─symbol─┘
symbol
is one of the following:
An ordinary symbol
A variable symbol that has been assigned a character string with a value
that is valid for an ordinary symbol
A sequence symbol
| The name is assigned to the next halfword aligned location. There may be a
| single byte before that location, but this is skipped for alignment. There may be
| zero or more NOP(R)s generated at or after that location.
byte
is an absolute expression that specifies at which even-numbered byte in a
| fullword, doubleword, or quadword the location counter is set. The value of the
expression must be 0 to boundary-2.
boundary
is an absolute expression that specifies the byte specified by boundary is in a
fullword, doubleword, or quadword. A value of 4 indicates the byte is in a
| fullword, a value of 8 indicates the byte is in a doubleword, and a value of 16
| indicates the byte is in a quadword.
Figure 29 shows valid pairs of byte and word.
Figure 29 (Page 1 of 2). Valid CNOP Values
Values
Specify
0,4 Beginning of a word
2,4 Middle of a word
0,8 Beginning of a doubleword
2,8 Second halfword of a doubleword
4,8 Middle (third halfword) of a doubleword
6,8 Fourth halfword of a doubleword
| 0,16
Beginning of a quadword
| 2,16
Second halfword of a quadword
| 4,16
Third halfword of a quadword
| 6,16
Fourth halfword of a quadword
| 8,16
Fifth halfword of a quadword
Chapter 5. Assembler Instruction Statements 119