Technical data

Cray Standard C/C++ Reference Manual
2.8 General Optimization Options
The following sections describe general optimization options.
2.8.1 -O level (CC, cc, c89)
Default option: Equivalent to the appropriate -h option
The -O level option specifies the optimization level for a group of compiler
features. Specifying -O with no argument is the same as not specifying the -O
option; this syntax is supported for compatibility with other vendors.
A value of 0, 1, 2,or3 sets that level of optimization for the -h inline,
-h scalar, -h task, and -h vector options.
For example, -O2 is equivalent to the following:
-h inline2,scalar2,task2,vector2
Optimization features specified by -O are equivalent to the following -h options
(taskn is ignored on UNICOS/mk systems):
Table 1. -h Option Descriptions
-h option
Description location
-h inlinen
Section 2.12.1, page 22
-h scalarn
Section 2.13.2, page 23
-h taskn
Section 2.11.1, page 20
-h vectorn
Section 2.10.3, page 19
2.8.2 -h [no]aggress (CC, cc)
Default option: -h noaggress
The -h aggress option provides greater opportunity to optimize loops that
would otherwise by inhibited from optimization due to an internal compiler size
limitation. -h noaggress leaves this size limitation in effect.
With -h aggress, internal compiler tables are expanded to accommodate larger
loop bodies. This option can increase the compilation’s time and memory size.
On UNICOS systems, this option also disables the limit on the number of vector
16 S–2179–36