HP Pascal/HP-UX Release Notes Version A.10.08

Chapter 1 17
New and Changed Features
Optimization Parameters
+O[no]fltacc
(continued)
Specifying +Ofltacc disables the generation of FMA
instructions as well as some other floating-point optimizations.
Use +Ofltacc if it is important that the compiler evaluate
floating-point expressions as it does in unoptimized code. The
+Ofltacc option does not allow any optimizations that change
the order of expression evaluation and therefore may affect the
result.
If you are optimizing code at level 2 or higher and do not specify
+Onofltacc or +Ofltacc, the optimizer will use FMA
instructions, but will not perform floating-point optimizations
that involve expression reordering or other optimizations that
potentially impact numerical stability.
The list below identifies the different actions taken by the
optimizer according to whether you specify +Ofltacc,
+Onofltacc, or neither option.
Optimization Expression FMA?
Options Reordering?
-----------------------------------------
+02 No Yes
+02 +Ofltacc No No
+02 +Onofltacc Yes Yes
+O[no]initcheck
Levels 2, 3, 4
The initialization checking feature of the optimizer has three
possible states: on, off, or unspecified.
When on (+Oinitcheck), the optimizer initializes to zero any
local, scalar, non-static variables that are uninitialized with
respect to at least one path leading to a use of the variable.
When off (+Onoinitcheck), the optimizer issues warning
messages when it discovers uninitialized variables, but does not
initialize them.
When unspecified, the optimizer initializes to zero any local,
scalar, non-static variables that are uninitialized with respect to
all paths leading to a use of the variable.
Use +Oinitcheck to look for uninitialized variables in a
program.
Advanced Option Optimization Performed