HP Fortran Programmer Guide (766160-001, March 2014)

Table 3 Options for controlling the front end (continued)
FunctionOption
Suppress warning messages.-w
Warn about all questionable constructs and issue remarks
about coding styles and performance. Without the +w
+w
option, the compiler issues warnings only about constructs
that are almost certainly problems.
Back-end
The two main functions of the back-end are:
• To optimize your program for faster performance
• To generate the code that goes into the object file
Optimization is performed by two subcomponents of the compiler’s back end:
• The High-Level Optimizer (HLO), which performs large-scale, high-semantic-level analyses and
transformations to increase performance.
• The low-level optimizer, which performs traditional optimizations (such as common
subexpression elimination and dead-code removal) as well as machine-specific optimizations.
Options for controlling optimization form the largest group of the command-line options. These
options enable you to do the following:
• To set the level of optimization that is applied to your program
• To apply a package of optimizations that meet certain requirements of your application—for
example, optimizations that favor compile-time speed over performance
• To apply specific optimization technologies to your program, or to specific parts of your
program, for fine-tuning performance
Table 4 (page 90) lists (in summary form) the options that control optimization. For information
about how to use these options, see
NOTE: If you use the f90 command to compile and link on separate command lines, many of
the optimization options must appear on both the command line and the link line; see “Performance
and optimization ” (page 87). For information about using f90 to compile and link, see “Linking
with f90 vs. ld” (page 50).
Table 4 Options for controlling optimization
FunctionOption
Check the use of stack variables before it is defined at
runtime.
+check=uninit
Perform memory hierarchy optimizations for the PA7200
processor.
+DC7200
Optimize program, where optlevel is 0 (no optimization),
1, 2, 3, or 4 (the highest level). If optlevel is not
specified, the program is optimized at level 2 (-O2).
-O[optlevel]
This option has the same meaning as the -O[optlevel]
option, except that optlevel must be specified. It is
provided for compatibility with makefiles.
+Ooptlevel
Back-end 13