O
- object files
- compile only, 3.4.7 –c
- name, 3.4.72 –o name
- object library search directories, 3.4.49 –Lpath
- obsolete command-line options, 3.3.4 Obsolete Option Flags
- octal, 4.2.1.2 Alternate Forms of Boolean Constants
- one-trip DO loops, 3.4.73 –onetrip
- OpenMP, 2.3.2.1 OpenMP Parallelization Directives
- directives summary, C.3 Fortran OpenMP Directives
- OPT directive, 2.3.1.5 The OPT Directive
- -xmaxopt option, 3.4.146 –xmaxopt[=n]
- optimization
- across source files
- 3.4.119 –xcrossfile[={1|0}]
- 3.4.131 –xipo[={0|1|2}]
- aliasing, 3.4.108 –xalias[=keywords]
- floating-point, 3.4.35 –fsimple[={1|2|0}]
- inline user-written routines, 3.4.44 –inline=[%auto][[,][no%]f1,…[no%]fn]
- interprocedural, 3.4.131 –xipo[={0|1|2}]
- levels, 3.4.65 –O[n]
- link-time, 3.4.144 –xlinkopt[={1|2|0}]
- loop unrolling, 3.4.99 –unroll=n
- loop unrolling by directive, 2.3.1.3 The UNROLL Directive
- math library, 3.4.141 –xlibmopt
- OPT directive
- 2.3.1.5 The OPT Directive
- 3.4.146 –xmaxopt[=n]
- PIPELOOP directive, 2.3.1.6 The PIPELOOP[=n] Directive
- PREFETCH directive, 2.3.1.7 The PREFETCH Directives
- specify cache, 3.4.114 –xcache=c
- specify instruction set architecture, 3.4.110 –xarch=isa
- specify processor, 3.4.116 –xchip=c
- target hardware, 3.4.57 –native
- vector library transformations with -xvector, 3.4.179 –xvector[= [[no%]lib, [no%]simd, %none] ]
- with -fast, 3.4.24 –fast
- with debugging, 3.4.39 –g
- options, See command-line options
- order of, functions, 3.4.122 –xF
- order of processing, options, 3.2 Options Syntax
- overflow
- stack, 3.4.91 –stackvar
- trap on floating-point, 3.4.37 –ftrap=t
- overindexing, aliasing, 3.4.108 –xalias[=keywords]