XL Fortran for AIX 8.1
Language Reference
XL Fortran provides several procedures that allow you to query and control
the floating-point status and control register of the processor
directly. These procedures are more efficient than the fpgets and
fpsets subroutines because they are mapped into inlined machine instructions
that manipulate the floating-point status and control register (fpscr)
directly.
XL Fortran supplies the module xlf_fp_util, which contains the
interfaces and data type definitions for these procedures and the definitions
for the named constants that are needed by the procedures. This module
enables type checking of these procedures at compile time rather than at link
time. You can use the argument names listed in the examples as the
names for keyword arguments when calling the procedure. The following
files are supplied for the modules xlf_fp_util:
| File names
| File type
| Locations
|
| xlf_fp_util.mod
| module symbol file (32-bit)
|
- /usr/lpp/xlf/include_32_d10
- /usr/lpp/xlf/include_32_d7
- Note:
- The files in these directories are exact copies of one another.
|
| module symbol file (64-bit)
| /usr/lpp/xlf/include_64
|
To use these procedures, you must add a USE XLF_FP_UTIL
statement to your source file. For more information on USE,
see USE.
If there are name conflicts (for example if the accessing subprogram has an
entity with the same name as a module entity), use the ONLY clause or
the renaming features of the USE statement.
For example,
USE XLF_FP_UTIL, NULL1 => get_fpscr, NULL2 => set_fpscr
When compiling with the -U option, you must code the names of
these procedures in all lowercase. We will show the names in lowercase
here as a reminder.
The fpscr procedures are:
- clr_fpscr_flags
- fp_trap
- get_fpscr
- get_fpscr_flags
- get_round_mode
- set_fpscr
- set_fpscr_flags
- set_round_mode
The following table lists the constants that are used with the fpscr
procedures:
| Family
| Constant
| Description
|
General
| FPSCR_KIND
| The kind type parameter for a fpscr flags variable
|
| FP_MODE_KIND
| The kind type parameter for fp_trap arguments and results
|
IEEE Rounding Modes
| FP_RND_RN
| Round toward nearest (default)
|
| FP_RND_RZ
| Round toward zero
|
| FP_RND_RP
| Round toward plus infinity
|
| FP_RND_RM
| Round toward minus infinity
|
| FP_RND_MODE
| Used to obtain the rounding mode from a fpscr flags variable or value
|
IEEE Exception Enable Flags(1)
| TRP_INEXACT
| Enable inexact trap
|
| TRP_DIV_BY_ZERO
| Enable divide-by-zero trap
|
| TRP_UNDERFLOW
| Enable underflow trap
|
| TRP_OVERFLOW
| Enable overflow trap
|
| TRP_INVALID
| Enable invalid trap
|
| FP_ENBL_SUMM
| Trap enable summary or enable all
|
IEEE Exception Status Flags
| FP_INVALID
| Invalid operation exception
|
| FP_OVERFLOW
| Overflow exception
|
| FP_UNDERFLOW
| Underflow exception
|
| FP_DIV_BY_ZERO
| Divide-by-zero exception
|
| FP_INEXACT
| Inexact exception
|
| FP_ALL_IEEE_XCP
| All IEEE exceptions summary flags
|
| FP_COMMON_IEEE_XCP
| All IEEE exceptions summary flags excluding the FP_INEXACT exception
|
Machine Specific Exception Details Flags
| FP_INV_SNAN
| Signalling NaN
|
| FP_INV_ISI
| Infinity - Infinity
|
| FP_INV_IDI
| Infinity / Infinity
|
| FP_INV_ZDZ
| 0 / 0
|
| FP_INV_IMZ
| Infinity * 0
|
| FP_INV_CMP
| Unordered compare
|
| FP_INV_SQRT
| Square root of negative number
|
| FP_INV_CVI
| Conversion to integer error
|
| FP_INV_VXSOFT
| Software request
|
Machine Specific Exception Summary Flags
| FP_ANY_XCP
| Any exception summary flag
|
| FP_ALL_XCP
| All exceptions summary flags
|
| FP_COMMON_XCP
| All exceptions summary flags excluding the FP_INEXACT exception
|
fp_trap constants(2)
| FP_TRAP_SYNC
| Precise trapping on
|
| FP_TRAP_OFF
| Trapping off
|
| FP_TRAP_QUERY
| Query trapping mode
|
| FP_TRAP_IMP
| Non-recoverable imprecise trapping on
|
| FP_TRAP_IMP_REC
| Recoverable imprecise trapping on
|
| FP_TRAP_FASTMODE
| Select fastest available mode
|
| FP_TRAP_ERROR
| Error condition
|
| FP_TRAP_UNIMPL
| Requested mode not available
|
Notes:
- In order to enable exception trapping, you must set the desired IEEE
Exception Enable Flags and,
- change the mode of the user process to allow floating-point exceptions to
generate traps with a call to fp_trap, or,
- compile your program with the appropriate -qflttrap
suboption. For more information on the -qflttrap
compiler option and its suboptions, see the User's
Guide.
- For more information on fp_trap constants, see fp_trap in Technical Reference: Base Operating System and
Extensions Volume 1.
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