| Option |
Description |
Default |
| Windows* |
Linux* |
| -fast |
-fast |
Enables -O3 and -Qipo
to enhance speed across the entire program. |
OFF |
| -G1 |
-tpp1 |
Itanium®-based
systems only
Target optimization to the Itanium processor. |
OFF |
| -G2 |
-tpp2 |
Itanium-based systems
only
Target optimization to the ItaniumŪ 2 processor. Generated code
is compatible with the Itanium processor. |
ON |
| -G5 |
-tpp5 |
IA-32 only
Targets the optimizations to the Intel® PentiumŪ processor.
|
OFF |
| -G6 |
-tpp6 |
IA-32 only
Targets the optimizations to the Intel Pentium Pro, Pentium II and
Pentium III processors. |
OFF |
| -G7 |
-tpp7 |
IA-32 only
Targets optimizations for the Intel Pentium 4 processors, Intel®
Xeon(TM) processors, Intel® Pentium® M processors, and Intel
processors code-named "Prescott".
|
ON |
| -O1 |
-O1 |
Optimizes for speed, but omits optimizations that tend to increase
object size for small speedups.
For the Itanium compiler, -O1 turns off
software pipelining to reduce code size.
Creates the smallest code in the majority of cases.
Use this option for applications sensitive to code size and code
locality, such as large database applications and code with many
branches and not dominated by loops
-O1 implies -Oi, but some applications that are sensitive to code
size and locality may benefit from -Oi. Hence, you may want to try
-O1 -Oi. |
OFF |
| -O2 |
-O2 |
Default setting. Optimizes for speed. The -O2 option
adds intrinsic function inlining to -O1
optimizations. The compiler may reassociate floating-point expressions
to improve application performance.
Creates the fastest code in most cases, but may increase code size
significantly more than -O1.
For best overall performance on typical integer applications that
do not make heavy use of floating point math. |
ON |
| -O3 |
-O3 |
Optimizes for speed. Enables high-level optimization. Same as
-O2, plus loop transformation and data
prefetching.
This level does not guarantee higher performance. Using this option
may increase the compilation time. Impact on performance is application
dependent, some applications may not see a performance improvement.
For applications that make heavy use of floating point calculations
on large data sets
Limited support for IA-32 C++ compiler for Linux*. See the User's
Guide for more information. |
OFF |
| -Od |
-O0 |
Disables optimizations. This option also replaces calls to math
intrinsics with calls to the standard runtime library.
You can use this option during the early stages of application
development, until you know the application is working correctly,
then move to a higher setting, usually -O2.
Does not utilize Itanium architecture features such as predication,
speculation,
and software pipelining,
so it generates poor code with lots of loads and stores.h |
OFF |
| -Oi[-] |
-nolib_inline |
Disables inline expansion of intrinsic functions.
|
OFF |
| -Qax{K|W|N|B|P} |
-ax{K|W|N|B|P} |
IA-32 only
Generates specialized code for processor-specific codes K, W, N,
B, and P while also generating generic IA-32 code.
- K = Intel Pentium III and compatible Intel processors.
- W = Intel Pentium 4 and compatible Intel processors.
- N = Intel Pentium 4 and compatible Intel processors.
- B = Intel Pentium M and compatible Intel processors.
- P = Intel processors code-named "Prescott".
|
OFF |
| -Qip |
-ip |
Enables interprocedural optimizations for single file compilation. |
OFF |
| -Qipo |
-ipo |
Enables interprocedural optimizations across files. |
OFF |
| -Qlong_double |
-long_double |
Changes the defaultsize of the long double
type from 64 to 80 bits.
This option introduces a number of incompatibilities with other
files compiled without this option and with calls to library routines.
Therefore, Intel recommends that the use of long
double variables be local to a single file when you compile
with this option. |
OFF |
|
-Op[-] |
-mp |
Enables [disables] conformance to the ANSI C and IEEE 754 standards for
floating-point arithmetic (subset of -Za
or -ansi).
Very precise; slows your application down
|
OFF |
| -Qopenmp> |
-openmp |
Enables the parallelizer to generate multi-threaded code based
on the OpenMP* directives. The -Qopenmp option works with
both -Od and any optimization level of -O1, -O2
(default ), and -O3. The support of -Od by OpenMP
helps to debug OpenMP applications. |
OFF |
| -Qpc{32|64|80} |
-pc{32|64|80} |
IA-32 only
Enables floating-point significand precision control. The value
is used to round the significand to the correct number of bits.
The value must be either 32, 64, or 80. |
-Qpc64 |
| -Qprec |
-mp1 |
IA-32 only
Improves floating-point precision with less performance degradation
than -Op. Almost, but not quite,
as precise as ANSI; faster than ANSI. All but the most costly operations
are done according to ANSI. |
OFF |
| -Qprec_div |
-prec_div |
IA-32 only
Disables the floating point division-to-multiplication optimization.
By default, the Intel compiler converts division operations into
reciprocal multiply operations, which is less precise but much faster. |
OFF |
| -Qprof_dir dirname |
|
Specifies the directory (dirname)
to hold profile information. |
OFF |
| -Qprof_gen[x] |
-prof_gen[x] |
Instruments the program to prepare for instrumented execution
and also creates a new static profile information file (.spi) |
OFF |
| -Qprof_use |
-prof_use |
Uses dynamic feedback information. |
OFF |
| -Qrcd |
-rcd |
IA-32 only
Enables [disables] fast conversions of floating-point-to-integer
conversions. Improves the performance of code that requires floating-point-to-integer
conversions. Can cause incorrect results for programs (esp. Fortran)
that depend on rounding.
|
OFF |
| -Qx{K|W|N|B|P} |
-x{K|W|N|B|P} |
IA-32 only
Generates specialized code for processor-specific codes K, W, N,
B, and P.
- K = Intel Pentium III and compatible Intel processors.
- W = Intel Pentium 4 and compatible Intel processors.
- N = Intel Pentium 4 and compatible Intel processors.
- B = Intel Pentium M and compatible Intel processors.
- P = Intel processors code-named "Prescott".
|
OFF |
| -Za |
-ansi |
Enforces strict conformance to the ANSI standard for C.
Slower and more precise than -Op. |
OFF |
| -Zi |
-g |
Enables generating debug information (.pdb for Windows Visual
C++*).
Adds info to the object file so that any particular assembly line
can be associated with its corresponding C code.
Use this option when tuning your application's performance using
the VTune™ Performance Analyzer or a similar tool. |
OFF |