Selecting one of the following will take you directly to that section:
Determines the version of the architecture for which the compiler generates instructions.
Possible values for architecture are:
SSE Optimizes for Intel Pentium 4 processors with Streaming SIMD Extensions (SSE).Default:
OFF No processor specific code is generatd by the compiler.
The -fast option enhances execution speed across the entire program by including the following options that can improve run-time performance:
-O3 (maximum speed and high-level optimizations)
-Qipo (enables interprocedural optimizations across files)
-QxT (generate code specialized for Intel Pentium 4 processor and compatible Intel processors with Streaming SIMD Extensions 3)
-Qprec-div- (disable -Qprec-div) where -Qprec-div improves precision of FP divides (some speed impact)
To override one of the options set by /fast, specify that option after the -fast option on the command line. The exception is the xP or QxP option which can't be overridden. The options set by /fast may change from release to release.
Enables optimizations for speed and disables some optimizations that
increase code size and affect speed.
To limit code size, this option:
- Enables global optimization; this includes data-flow analysis,
code motion, strength reduction and test replacement, split-lifetime
analysis, and instruction scheduling.
- Disables intrinsic recognition and intrinsics inlining.
The O1 option may improve performance for applications with very large
code size, many branches, and execution time not dominated by code within loops.
On IA-32 Windows platforms, -O1 sets the following:
/Qunroll0, /Oi-, /Op-, /Oy, /Gy, /Os, /GF (/Qvc7 and above), /Gf (/Qvc6 and below), /Ob2, and /Og
Enables optimizations for speed. This is the generally recommended
optimization level. This option also enables:
- Inlining of intrinsics
- Intra-file interprocedural optimizations, which include:
- inlining
- constant propagation
- forward substitution
- routine attribute propagation
- variable address-taken analysis
- dead static function elimination
- removal of unreferenced variables
- The following capabilities for performance gain:
- constant propagation
- copy propagation
- dead-code elimination
- global register allocation
- global instruction scheduling and control speculation
- loop unrolling
- optimized code selection
- partial redundancy elimination
- strength reduction/induction variable simplification
- variable renaming
- exception handling optimizations
- tail recursions
- peephole optimizations
- structure assignment lowering and optimizations
- dead store elimination
On IA-32 Windows platforms, -O2 sets the following:
/Og, /Oi-, /Os, /Oy, /Ob2, /GF (/Qvc7 and above), /Gf (/Qvc6 and below), /Gs, and /Gy.
Enables O2 optimizations plus more aggressive optimizations,
such as prefetching, scalar replacement, and loop and memory
access transformations. Enables optimizations for maximum speed,
such as:
- Loop unrolling, including instruction scheduling
- Code replication to eliminate branches
- Padding the size of certain power-of-two arrays to allow
more efficient cache use.
On IA-32 and Intel EM64T processors, when O3 is used with options
-ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler
performs more aggressive data dependency analysis than for O2, which
may result in longer compilation times.
The O3 optimizations may not cause higher performance unless loop and
memory access transformations take place. The optimizations may slow
down code in some cases compared to O2 optimizations.
The O3 option is recommended for applications that have loops that heavily
use floating-point calculations and process large data sets. On IA-32
Windows platforms, -O3 sets the following:
/GF (/Qvc7 and above), /Gf (/Qvc6 and below), and /Ob2
This option tells the compiler to assume that the program adheres to ISO C Standard aliasability rules. If your program adheres to these rules, then this option allows the compiler to optimize more aggressively. If it doesn't adhere to these rules, then it can cause the compiler to generate incorrect code.
This option instructs the compiler to analyze and transform the program so that 64-bit pointers are shrunk to 32-bit pointers, and 64-bit longs (on Linux) are shrunk into 32-bit longs wherever it is legal and safe to do so. In order for this option to be effective the compiler must be able to optimize using the -ipo/-Qipo option and must be able to analyze all library/external calls the program makes. This option requires that the size of the program executable never exceeds 2**32 bytes and all data values can be represented within 32 bits. If the program can run correctly in a 32-bit system, these requirements are implicitly satisfied. If the program violates these size restrictions, unpredictable behavior might occur.
Enable C++ Exception Handling and RTTI This option has the same effect as specifying /GX /GR.
This option enables additional interprocedural optimizations for single file compilation. These optimizations are a subset of full intra-file interprocedural optimizations. One of these optimizations enables the compiler to perform inline function expansion for calls to functions defined within the current source file.
Multi-file ip optimizations that includes:
- inline function expansion
- interprocedural constant propogation
- dead code elimination
- propagation of function characteristics
- passing arguments in registers
- loop-invariant code motion
Specifies whether streaming stores are generated.
Possible values are:
always: Enables generation of streaming stores for optimization. The compiler optimizes under the assumption that the application is memory bound.
never : Disables generation of streaming stores for optimization. Normal stores are performed.
auto : Lets the compiler decide which instructions to use.
This option enables prefetch insertion optimization. To use this option, you must also specify O3. The goal of prefetching is to reduce cache misses by providing hints to the processor about when data should be loaded into the cache. To disable the prefetch insertion optimization, use -no-prefetch (Linux) or /Qprefetch- (Windows).
This option improves precision of floating-point divides. It has a slight impact on speed.
With some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.
However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, use this option to disable the floating-point division-to-multiplication optimization. The result is more accurate, with some loss of performance.
If you specify -no-prec-div (Linux and Mac OS) or /Qprec-div- (Windows), it enables optimizations that give slightly less precise results than full IEEE division.
This option enables scalar replacement performed during loop transformation. To use this option, you must also specify O3. -Qscalar-rep- disables this feature. (default)
Possible values are:
K Code is optimized for Intel Pentium III and compatible Intel processors.
W Code is optimized for Intel Pentium 4 and compatible Intel processors.
N Code is optimized for Intel Pentium 4 and compatible Intel processors with Streaming SIMD Extensions 2.
The resulting code may contain unconditional use of features that are not supported on other processors.
This option also enables new optimizations in addition to Intel processor-specific optimizations including
advanced data layout and code restructuring optimizations to improve memory accesses for Intel processors.
B Code is optimized for Intel Pentium M and compatible Intel processors.
This option also enables new optimizations in addition to Intel processor-specific optimizations.
P Code is optimized for Intel Core Duo processors, Intel Core Solo processors,
Intel Pentium 4 processors with Streaming SIMD Extensions 3, and compatible Intel processors with
Streaming SIMD Extensions 3.
The resulting code may contain unconditional use of features that are not supported on other processors.
This option also enables new optimizations in addition to Intel processor-specific optimizations
including advanced data layout and code restructuring optimizations to improve memory accesses for
Intel processors.
T Code is optimized for Intel Core2 Duo processors, Intel Core2 Extreme processors, and the
Dual-Core Intel Xeon processor 5100 series.
This option also enables new optimizations in addition to Intel processor-specific optimizations
including advanced data layout and code restructuring optimizations to improve memory accesses
for Intel processors
Do not use these options if you are executing a program on a processor that is not an Intel processor. If you use this option on a non-compatible processor to compile the main program (in Fortran) or the function main() in C/C++, the program will display a fatal run-time error if they are executed on unsupported processors.
In particular, such programs compiled with processor values N, B, or P will display a fatal run-time error if they are executed on unsupported processors.
Instrument program for profiling for the first phase of two-phase profile guided otimization. This instrumentation gathers information about a program's execution paths and data values but does not gather information from hardware performance counters. The profile instrumentation also gathers data for optimizations which are unique to profile-feedback optimization.
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -Qprof_use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
This option enables C++ exception handling.
Enables C++ Run Time Type Information (RTTI).
Enable SmartHeap library usage by forcing the linker to ignore multiple definitions
Enable SmartHeap library usage by forcing the linker to ignore multiple definitions
32-bit MicroQuill SmartHeap Library 8.0 for Windows available from http://www.microquill.com/
64-bit MicroQuill SmartHeap Library 8.0 for Windows available from http://www.microquill.com/
set the stack reserve amount specified to the linker
Tells the compiler the maximum number of times to unroll loops.
This option tells the compiler to assume there is no aliasing.
Disables inline expansion of all intrinsic functions.
Disables conformance to the ANSI C and IEEE 754 standards for floating-point arithmetic.
Allows use of EBP as a general-purpose register in optimizations.
This option enables most speed optimizations, but disables some that increase code size for a small speed benefit.
This option enables global optimizations.
Specifies the level of inline function expansion.
Ob0 - Disables inlining of user-defined functions. Note that statement functions are always inlined.
Ob1 - Enables inlining when an inline keyword or an inline attribute is specified. Also enables inlining according to the C++ language.
Ob2 - Enables inlining of any function at the compiler's discretion.
This option tells the compiler to separate functions into COMDATs for the linker.
This option enables read only string-pooling optimization.
This option enables read/write string-pooling optimization.
This option disables stack-checking for routines with 4096 bytes of local variables and compiler temporaries.
Enable complex math routines when using Microsoft Visual Studio 2005.
Tell the compiler not to use the internal VA_COPY which is not needed when using Microsoft Visual Studio 2005
Compile the source for the Intel compiler on Windows.
Pass the command to the C/C++ pre-processor.
For mixed-language benchmarks, tell the compiler to convert routine names to lowercase for compatibility
For mixed-language benchmarks, tell the compiler to assume that routine names end with an underscore
Tell the compiler to treat source files as C++ regardless of the file extension
Tell the compiler to append an underscore to external subroutine names
Tell the compiler to change routine names to all lowercase (same as /names:lowercase)
Tell the compiler to specify the level of compatibility to adhere to with Fortran PowerStation
Invoke the Intel C++ compiler
Invoke the Intel Fortran compiler
Tells the compiler to conform to the ISO/IEC 9899:1999 International Standard.
Tell the compiler to not display compiler version information under compilation
Tell the compiler to print only errors under compilation
Tell the compiler to add directory to include file search path under compilation