HP aC++/HP C A.06.28 Programmer's Guide Integrity servers (769150-001, March 2014)
Table 4 Options for +FP[flags]
DescriptionFlag
Trap on invalid floating-point operations.V (v)
Trap on divide by zero.Z (z)
Trap on floating-point overflow.O (o)
Trap on floating-point underflow.U (u)
Trap on floating-point operations that produce inexact results.I (i)
Enable sudden underflow (flush to zero) of denormalized values.D (d)
To dynamically change these settings at runtime, see fesetenv(3M).
+FPmode
+FPmode specifies how the run-time environment for floating-point operations should be initialized
at program start up. By default, modes are as specified in the IEEE floating-point standard: all traps
disabled, gradual underflow, and rounding to nearest. See ld(1) for specific values of mode.
To dynamically change these settings at run time, refer to fenv(5), fesettrapenable(3M),
and fesetround(3M).
+O[no]libmerrno
+O[no]libmerrno
Description:
The +O[no]libmerrno option enables [disables] support for errno in libm functions. The
default is +Onolibmerrno for C++, c99, or –AC99.
In C-mode, the default is +Olibmerrno with -Aa option.
+Oprefetch_latency
+Oprefetch_latency=cycles
The +Oprefetch_latency option applies to loops for which the compiler generates data prefetch
instructions. cycles represents the number of cycles for a data cache miss. For a given loop, the
compiler divides cycles by the estimated loop length to arrive at the number of loop iterations
for which to generate advanced prefetches.
cycles must be in the range of 0 to 10000. A value of 0 instructs the compiler to use the default
value, which is 480 cycles for loops containing floating-point accesses and 150 cycles for loops
that do not contain any floating-point accesses.
For tuning purposes, it is recommended that users measure their application’s performance using
a few different prefetch latency settings to determine the optimal value. Some floating-point codes
may benefit by increasing the distance to 960. Parallel applications frequently benefit from a
shorter prefetch distance of 150.
+O[no]preserved_fpregs
+O[no]preserved_fpregs
The +O[no]preserved_fprefs option specifies whether the compiler is allowed [not allowed]
to make use of the preserved subset of the floating-point register file as defined by the Itanium
runtime architecture.
The default is +Opreserved_fpregs.
44 Command-Line Options