/OPTIMIZE[=LEVEL=n]
/OPTIMIZE=TUNE=option
/OPTIMIZE=LEVEL=4 (D)
/OPTIMIZE=TUNE=GENERIC (D)
/NOOPTIMIZE
Controls how the compiler produces optimized code.
The default is /OPTIMIZE, which is the same as /OPTIMIZE=(LEVEL=4,
TUNE=GENERIC). For a debugging session, use the negative form
(/NOOPTIMIZE or /OPTIMIZE=LEVEL=0) to ensure that the debugger has
sufficient information to locate errors in the source program.
In most cases, using /OPTIMIZE will make the program execute
faster. As a side effect of getting the fastest execution speeds,
using /OPTIMIZE can produce larger object modules and longer
compile times than /NOOPTIMIZE.
LEVEL=n
You can select one of the following levels:
0 Has the same effect as /NOOPTIMIZE. All
optimizations are turned off.
1 Has some optimizations (such as instruction
scheduling).
2 Adds more optimizations (such as loop unrolling
and split lifetime analysis) to those in level 1.
3 Adds more optimizations (such as decimal
shadowing) to those in level 2. All
optimizations are turned on.
4 Is identical to level 3. /OPTIMIZE=LEVEL=4 is the
equivalent of /OPTIMIZE or not specifying /OPTIMIZE.
Specify /NOOPTIMIZE if you specify /DEBUG when compiling a program.
/NOOPTIMIZE expedites and simplifies your debugging session by
putting the machine code in the same order as the lines in the
source program. Optimizations can cause unexpected and confusing
behavior in a debugging session. For more information about
debugging your program with the /NOOPTIMIZE qualifier, see the
COBOL User Manual.
Specify /NOOPTIMIZE if you specify /MACHINE_CODE when compiling
a program to ensure that the machine code listing reflects the
actual code executed for a given statement as well as the order
of execution.
The /NOOPTIMIZE qualifier is also useful in conjunction with
/CHECK, as optimization can make checking more difficult.
Specifying /OPTIMIZE, the default, usually makes programs run
faster. However, using /OPTIMIZE produces extra instructions
to perform the optimization, which may result in larger object
modules and longer compile times than the /NOOPTIMIZE qualifier.
To speed compilations during program development, you may want
to compile with the /NOOBJECT qualifier when you want to check
syntax, with /NOOPTIMIZE when you check for correct execution,
and later with /OPTIMIZE for your final check. For more
information about optimizing your program with the /OPTIMIZE
qualifier, see the COBOL User Manual.
TUNE=keyword
Specifies the kind of optimized code to be generated. The
keyword can be any of the following:
Keyword Meaning
------- -------
GENERIC Generates and schedules code that will execute
well for both generations of Alpha processors.
This provides generally efficient code for those
cases where both processor generations are likely
to be used.
HOST Generates and schedules code optimized for the
processor generation in use on the system being
used for compilation.
EV4 Generates and schedules code optimized for the
21064, 21064A, 21066, and 21068 implementations
of the Alpha chip.
EV5 Generates and schedules code optimized for the
21164 implementation of the Alpha chip. This
processor generation is faster than EV4.
EV56 Generates code for some 21164 chip implementations
that use the byte and word manipulation instruction
extensions of the Alpha architecture.
Running programs compiled with the EV56 keyword
may incur emulation overhead on EV4 and EV5
processors, but will still run correctly on
OpenVMS Alpha V7.1 (or later) systems.
EV6 Generates and schedules code for the 21264 chip
implementation that uses the following extensions
to the base Alpha instruction set: BWX (Byte/Word
manipulation) and MAX (Multimedia) instructions,
square root and FIX (Floating-point convert) instructions.
Running programs compiled with the EV6 keyword
may incur emulation overhead on EV4, EV5, EV56,
and PCA56 processors, but will still run correctly on
OpenVMS Alpha V7.1 (or later) systems.
EV67,EV68 Generates and schedules code for the 21264A chip
implementation that uses the following extensions
to the base Alpha instruction set: BWX (Byte/Word
manipulation) and MAX (Multimedia) instructions,
square root and FIX (Floating-point convert) instructions,
and CIX (Count) instructions.
Running programs compiled with the EV67 or EV68 keywords
may incur emulation overhead on EV4, EV5, EV56, EV6,
and PCA56 processors, but will still run correctly on
OpenVMS Alpha V7.1 (or later) systems.
PCA56 Generates code for the 21164PC chip implementation
that uses the byte and word manipulation instruction
extensions and multimedia instruction extensions
of the Alpha architecture.
Running programs compiled with the PCA56 keyword
may incur emulation overhead on EV4, EV5, and
EV56 processors, but will still run correctly on
OpenVMS Alpha V7.1 (or later) systems.
/OPTIMIZE=TUNE is currently ignored on OpenVMS I64.