Accelerator Manual (G06.24+, H06.03+)

Setting Accelerator Options
Accelerator Manual—527303-002
5-2
Atomicity of Instructions
The Table 5-1, Accelerator Super Options, on page 5-2 shows the settings of the
elementary options for each super option.
You can set super options for an entire program only. You can set elementary options
for an entire program or for individual procedures. (In terms of setting Accelerator
options, FORTRAN routines and COBOL programs are equivalent to procedures.
COBOL paragraphs are equivalent to subprocedures; you cannot set Accelerator
options for subprocedures.) For example, OvTrap_On sets the option on for an entire
program, whereas OvTrap_On MYPROC only sets the option on for the procedure
MYPROC. You can also set Accelerator options for a particular code space using the
Accelerator scoping directives. Refer to Section 3, Preparing Your Program for the
Accelerator for details on scoping directives.
The Accelerator is not case sensitive except for procedure names that are enclosed
within single quotes. C procedure names must be entered in single quotes, such as:
ATOMIC_ON 'MyProc'
The most common strategy for using the Accelerator is to select the Common super
option and then override elementary options for individual procedures that require the
“on” setting. For example, if you know that most of the program Myprog does not rely
on instruction atomicity, or inheritance of condition codes, but that procedure
GETUSERTERM expects condition codes from the calling procedure, you would
specify the following:
AXCEL MYPROG, output-file; COMMON, InheritsCC_On GETUSERTERM
Atomicity of Instructions
Atomic instructions always complete a series of memory operation without interruption;
another instruction cannot execute until the atomic instruction is finished. The
Accelerator option default setting, Atomic_Off, generates code that executes most
instructions as non-atomic. The following instructions execute as atomic on TNS
systems and non-atomic on TNS/R systems (in accelerated code only). They might
result in an incorrectly running accelerated program:
ANG DFG ORG ADM
ANS DFS ORS
ANX DFX ORX
Table 5-1. Accelerator Super Options
Atomic InheritsCC OvTrap SafeAliasingRules TruncateIndexing
Common OFF OFF ON ON ON
Fast OFF OFF OFF OFF OFF
Safe ON ON ON ON ON