FLAG DESCRIPTIONS             Sun C, C++ and Fortran
Sun ONE Studio 7 (formerly Forte[tm] Developer 7)
and Forte[tm] Developer 6 update 2
Last updated: 6/18/2002




Set definition for preprocessor.


Assume data is naturally aligned.


Specify static binding.


Accept extended (132 character) input source lines (FORTRAN).


This is a convenience option for selecting a set of optimizations for performance. In all three of Fortran, C, and C++, -fast implies:

  • -dalign, align memory objects on their natural boundaries (also spelt as -xmemalign=8s, meaning that doubles (8 byte) items are correctly aligned, and if an incorrect item is found, a signal should be raised).
  • -fsimple=2 permitting reordering of floating point operations.
  • -fns disable gradual underflow
  • -libmil use inline expansion for math library, libm (also spelt -xlibmil)
  • Optimization level 5 (spelt either as -O5 or -xO5)
  • -xtarget=native, the native best machine characteristics option (also sometimes spelt -native). This option implies all three of -xarch=native, -xchip=native, -xcache=native

In addition, the -fast option sets the following options for the compilers noted:

  • -depend (Fortran and C): analyze loops for data dependendencies (also spelt -xdepend)
  • -D__MATHERR_ERRNO_DONTCARE (C): errno may not be set for math functions.
  • -fsingle (C): evaluate float expressions as single precision
  • -ftrap=%none (f77, C, C++) turn off IEEE 754 trapping
  • -ftrap=common (f90) limit IEEE 754 trapping to common cases
  • -xlibmopt (Fortran and C++): select the optimized math library
  • -pad=local (Fortran): pad local variables
  • -xalias_level=basic (C) assume ISO C9X aliasing rules for basic types only.
  • -xbuiltin=%all (C and C++): substitute intrinsic functions or inline system functions where profitable for performance.
  • -xprefetch=yes (Fortran and C): enable prefetching
  • -xprefetch_level=2 (Fortran): set the level of searching that the prefetcher will do (valid values are 1, 2, or 3, where higher values mean more searching)
  • -xvector=yes (Fortran): permits the compiler to transform math library calls within DO loops into single calls to the equivalent vector math routines when such transformations are possible.


Accept fixed-format input source files (FORTRAN).


Disable gradual underflow, allowing tiny results to be flushed to zero rather than producing subnormal numbers (non-standard according to IEEE 754)


Permits no simplifying assumptions. Preserves strict IEEE 754 conformance.


With -fsimple=1, the optimizer can assume the following:

  • The IEEE 754 default rounding/trapping modes do not change after process initialization.
  • Computations producing no visible result other than potential floating-point exceptions may be deleted.
  • Computations with Infinity or NaNs as operands need not propagate NaNs to their results. For example, x*0 may be replaced by 0.
  • Computations do not depend on sign of zero.


Permits more aggressive floating point optimizations that may cause programs to produce different numeric results due to changes in rounding. Even with -fsimple=2, the optimizer still is not permitted to introduce a floating point exception in a program that otherwise produces none.


Sets the IEEE 754 trapping mode in effect at startup.

t is a comma-separated list that consists of one or more of the following: %all, %none, common, [no%]invalid, [no%]overflow, [no%]underflow, [no%]division, [no%]inexact.

The default is -ftrap=%none for f77, C, and C++; for f90 the default is common.

This option sets the IEEE 754 trapping modes that are established at program initialization. Processing is left-to-right. The common exceptions, by definition, are invalid, division by zero, and overflow.

%none turns off all trapping modes.
common traps on invalid, division by zero, and overflow.

Do not use this option for programs that depend on IEEE standard exception handling; you can get different numerical results, premature program termination, or unexpected SIGFPE signals.


Use inline expansion templates for libm.


Use "classic" (pre 1998 C++ standard) iostream library

Prior to the C++ standard (1998), there was one iostream library, what is now often called "classic" iostreams. The C++ standard defines a different, but similar, iostream library, which we call "standard" iostreams. To get classic iostreams in standard (default) mode, you use the option "-library=iostream".


Library containing chip specific memory routines.


Link with math library


This chooses the math library that is optimized for speed


Library to enable Intimate Shared Memory (ISM) (4MB page) usage.


Link with the Sun Performance Library (netlib and Society for Industrial and Applied Mathematics (SIAM) routines)


Select native machine characteristics for optimization. Equivalent to setting all three of -xarch=native, -xchip=native, -xcache=native


See -Wc,-Qicache-chbab=1

-Qoption <phase>

Pass flags along to compiler phase:
   f90comp Fortran first pass
   iropt Global optimizer
   cg Code generator

-Qoption cg

See -Wc,<flags> below. (The code generation phase is addressed via -Qoption cg in Fortran and C++; and via -Wc in C.)

-Qoption f90comp

Enable padding of f90 arrays by n.

-Qoption f90comp

Enable f90 array expansion.

-qoption f90comp

This reduces the optimization level of the f90 front/middle end to O3. The effect is to turn off loop cloning and unrolling (note that it has no effect on cg's loop unrolling).

-Qoption iropt

See also -W2,<flags> below. (The optimizer can be addressed either via Qoption iropt in Fortran and C++, or via -W2 in C.)

-Qoption iropt

enable optimizations based on data access patterns

-Qoption iropt

Set memory store operation weight for loop interchange to 9

-Qoption iropt

See -W2,-Amemopt

-Qoption iropt

See -W2,-Ma<n>

-Qoption iropt

See -W2,-Mm<n>

-Qoption iropt

Do not inline calls when parameters are arrays and actual array dimensions and formal array dimensions are mismatched

-Qoption iropt

See -W2,-Mr<n>

-Qoption iropt

disable scalar replacement optimization

-Qoption iropt

Same as -Qoption iropt -Rscalarrep plus -Qoption iropt -MR

-Qoption iropt

See -W2,-whole


Allocate routine local variables on stack (FORTRAN).


Pass flags along to compiler phase (2=optimizer, c=code generator)


Enable aggressive optimizations of all branches.


Enable optimizations based on data access patterns.


Allows the compiler to recognize malloc-like memory allocation functions.


Perform Inter-Procedural Analysis (IPA) -based inlining.


More aggresive strength reduction by replicating loops.


Memory access optimization. This does whole-program mode inter-procedural memory access analysis, merges memory allocations, and performs cache conscious data layout program transformations.


Reconstruct array subscripts during memory allocation merging and data layout program transformation


Convert multiple short memory operations into single long memory operations.


Enables outer-loop unrolling.


Enable optimization of critical control paths


Enable inlining of routines with frame size up to n.


Maximum module increase limit for inlining.


Procedures with entry counts equal or greater than n become candidates for inlining.


Maximum code increase due to inlining is limited to n triples.


Maximum level of recursive inlining.


The maximum size of a routine body eligible for inlining is limited to n triples.


Assume that different global pointer variables point to their own memory locations.


Turns on loop rerolling.


Do whole program optimizations.


Enable early cross-call instruction scheduling.


Allow generating speculative load during EPS.


Use enhanced pipeline scheduling(EPS) and selective scheduling algorithms for instruction scheduling.


Turn off register pressure heuristic in EPS.


Sets the aggressiveness of the trace formation.


Turns on the late trace scheduler.


Turns on the conversion of loads to non-faulting loads inside the trace.


Turn on optimization to reduce branch after branch penalty


Inline calls to memcpy with n bytes or fewer being copied


Use profile feedback data to predict values and attempt to generate faster code along these control paths, even at the expense of possibly slower code along paths leading to different values. Correct code is generated for both paths.


Do function entry alignment at n-byte boundaries.


Peels the most frequent test branches/cases off a switch until the branch probability reaches less than 1/n. This is effective only when profile feedback is used


Control irregular loop prefetching.
lp=1 turns on the module (default is on for F90; off for C/C++)
av Sets the prefetch look ahead to <nav>.
t Make <nt> attempts at prefetching.
fa=1 forces user settings to override internally computed values.
fl=1 forces the optimization to be turned on for all languages.


Use fp divide for signed integer division


Turn off prefetching within modulo scheduling


Disables the max live base registers algorithm for sethi hoisting.


Assume ANSI C conformance, allow K & R extensions. (default mode)

(C compiler)

Allows compiler to perform type-based alias analysis at the given alias level.
   basic assume ISO C9X aliasing rules for basic types only.
   std assume ISO C9X aliasing rules.
   strong assume all pointers are type safe (strongly typed).

(C++ compiler)

Allows compiler to perform type-based alias analysis at the given alias level.
   any assume any type may alias any other type.
   simple assume fundamental types are not aliased.
   compatible assume layout-incompatible types are not aliased.


Limit the set of instructions the compiler may use to generic, generic64, native, native64, v7, v8a, v8, v8plus, v8plusa, v8plusb, v9, v9a, v9b. Typical settings include:
UltraSPARC-II, 32-bit mode: v8plusa
UltraSPARC-II, 64-bit mode: v9a
UltraSPARC-III, 32-bit mode: v8plusb
UltraSPARC-III, 64-bit mode: v9b
For more information, see the Fortran User's Guide at docs.sun.com


Assume strict ANSI C conformance.


Defines the cache properties for use by the optimizer. c must be one of the following:

  • native (set parameters for the host environment)
  • s1/l1/a1
  • s1/l1/a1:s2/l2/a2
  • s1/l1/a1:s2/l2/a2:s3/l3/a3

The si/li/ai are defined as follows:
si The size of the data cache at level i, in kilobytes.
li The line size of the data cache at level i, in bytes.
ai The associativity of the data cache at level i.


Specifies the target processor for use by the optimizer. c must be one of: generic, generic64, native, native64, old, super, super2, micro, micro2, hyper, hyper2, powerup, ultra, ultra2, ultra2i, ultra3, 386, 486, pentium, pentium_pro, 603, 604.


Enable cross-file inlining.


Analyze loops for data dependencies.


Allow function reordering by the WorkShop Performance Analyzer


Turn off inlining


Performs optimizations across all object files in the link step: 0=off, 1=on, 2=performs whole-program detection and analysis


This chooses the math library that is optimized for speed.


Link with Sun supplied licensed sunperf library.


Does basic local optimization (peephole).


xO1 and more local and global optimizations.


Besides what xO2 does, it optimizes references or definitions for external variables. Loop unrolling and software pipelining are also performed.


xO3 plus function inlining.


Besides what -xO4 does, it enables speculative code motion.


Pad common block variables, for better use of cache. n specifies the amount of padding to apply. If no parameter is specified then the compiler selects one automatically.


Pad local variables only, for better use of cache. n specifies the amount of padding to apply. If no parameter is specified then the compiler selects one automatically.


Use parallel processing to improve performance.


Enable prefetch instructions on those architectures that support prefetch, such as UltraSPARC II (-xarch=v8plus, v8plusa, v9plusb, v9, v9a, or v9b)

  • auto Enable automatic generation of prefetch instructions
  • no%auto Disable automatic generation of prefetch instructions
  • explicit Enable explicit prefetch macros
  • no%explicit Disable explicit prefetch macros
  • yes the same as -xprefetch=auto,explicit
  • no the same as -xprefetch=no%auto,no%explicit

Defaults: If -xprefetch is not specified, -xprefetch=no%auto,explicit is assumed. If only -xprefetch is specified, -xprefetch=auto,explicit is assumed.


The compiler searches for prefetch opportunities when -xprefetch=auto is enabled. You can control the level of searching that the compiler does by setting n to 1, 2, or 3, where higher numbers mean do more searching. The default is 2.


Collect profile data for feedback directed optimizations.


Use data collected for profile feedback.


Parallelize loops containing reductions.


Allows use of the system reserved registers %g6 and %g7, and %g5 if not already allowed by -xarch value.


Treat pointer-valued function parameters as restricted pointers. The default is %none. Specifying -xrestrict is equivalent to specifying -xrestrict=%all.


Enables the use of non-faulting loads when used in conjunction with -xarch=v8plus. Assumes that no memory based traps will occur.


Represents unsuffixed floating-point constants as single precision


Assume K & R conformance, allow ANSI C.


Same as -native

Kernel Parameters




Minimum size of system V shared memory segment that can be created.


Maximum size of system V shared memory segment that can be created. This parameter is an upper limit that is checked before the system sees if it actually has the physical resources to create the requested memory segment.


System wide limit on number of shared memory segments that can be created.


Limit on the number of shared memory segments that any one process can create.

Environment Variables




Specify the locations to resolve dynamic link dependencies

By default, the runtime linker looks in only one standard place for dependencies: /usr/lib for 32-bit dependencies, or /usr/lib/64 for 64-bit dependencies. Any dependency specified as a simple filename is prefixed with this default directory name and the resulting pathname is used to locate the actual file.

If you have more than one release of the compilers installed, the environment variable LD_LIBRARY_PATH may be set to a colon-separated list of directories to enable dependencies to be resolved by any of them. Typical usages could include, depending on the location where you chose to install the compilers:



Note: <release> is specific for each release of Sun WorkShop software.

The latter example specifies the dynamic libraries specific to the v8plusb architecture (See -xarch). For more information see the C++ User's Guide at docs.sun.com


Set the heap size limit for large pages


Large page mode: Attempt to put text, data and heap all into large pages.