iec - Instruction Emulator Control
iec p|s [value]
iec p|s [keyword]
The following options are used with the iec command: Sets or displays the current option setting for the parent process. Sets or displays the current option setting for the system.
The following keywords are used with the p option: Resets the current option settings to the default settings for the parent process. Does not print the instruction emulation warning message for the parent process. Disables instruction emulation. Any programs that attempt to execute instructions that are not implemented in the host processor will receive the SIGILL (illegal instruction) signal. Prints the instruction emulation warning messages for all instances of instruction emulation. By default, a message is only printed for the first instance.
The following keywords are used with the s option: Resets the current option settings to the default settings for the system. Does not print the instruction emulation warning message for the system.
If value is not specified, the current option setting is displayed. You can specify value as either 0 (zero) or 1 (one). If value is 0 (zero), the option is turned on and messages are not displayed. If value is 1 (one), the option is turned off and messages are displayed.
Keywords can be used singly or in any combination. However, the reset keyword overrides any other keywords that it is used with.
Usually, the parent process is the shell.
Some processors in the Alpha processor family do not implement all of the instructions defined in the Alpha architecture. The operating system provides an instruction emulator that permits all programs written for the Alpha architecture to run, regardless of the Alpha processor being used.
When the operating system encounters an instruction that is not implemented by the host processor, the default action is to emulate the instruction and print a message informing the user process that the emulation has occurred. By default, the operating system prints a message only for the first instance of emulation, although it continues to emulate any other non-implemented instructions that it encounters. The message has the form: ``inst emulated pid=nnn <prog_name> va=0xvirtual_addrpc=0xpc_addr inst=0xactual_instr''. Receiving this message tells you that your application will run at less than its optimal level of performance. You may wish to recompile your program to get better performance. For information on how to compile for a specific hardware platform, see the compiler manpage for the language you are using.
In addition, the default action for the operating system is to not deliver a SIGILL signal to the parent process when an emulated instruction is encountered.
These defaults are satisfactory for most users, but some users require a different behavior and want to specify their own Instruction Emulator Control (IEC).
command enables or disables the display of
messages. The command sets or displays the
flags, as defined in
You must be superuser to set the system option.
Both of the following commands disable messages for the parent process: # iec p 0
# iec p noprint Both of the following commands enable messages for the system: # iec s 1
# iec s reset The following command enables the printing of a message for each emulated instruction: # iec p verbose