Base Compiler Invocation
C benchmarks
-
- icl
![[user]](http://www.spec.org/auto/cpu2006/flags/user.png)
- CC, LD
-
Invoke the Intel C++ compiler
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- -Qstd=c99
- CC, LD
-
Tells the compiler to conform to the ISO/IEC 9899:1999 International Standard.
C++ benchmarks
-
- icl
- CXX, LD
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Invoke the Intel C++ compiler
Invoke the Intel C++ compiler
Tells the compiler to conform to the ISO/IEC 9899:1999 International Standard.
Invoke the Intel C++ compiler
Invoke the Intel C++ compiler
Tells the compiler to conform to the ISO/IEC 9899:1999 International Standard.
Invoke the Intel C++ compiler
![[benchmark]](http://www.spec.org/auto/cpu2006/flags/benchmark.png)
SPEC_CPU_WIN32 sets up types for gcc's compile time arithmetic, reflects the lack of a unistd.g file, sets the size and existence of the __int64 type, and sets the default page size on Windows.
This flag can be used as a portability flag on systems which do not have the standard header file "stdint.h". Inclusion of this flag defines the value of INT64_MIN (if it is not defined) and sets the "int64" type (if it is not set already)
This flag is set when building 464.h264ref on Windows systems.
Pass the command to the C/C++ pre-processor.
SPEC_CPU_WIN32 sets up types for gcc's compile time arithmetic, reflects the lack of a unistd.g file, sets the size and existence of the __int64 type, and sets the default page size on Windows.
This flag can be used as a portability flag on systems which do not have the standard header file "stdint.h". Inclusion of this flag defines the value of INT64_MIN (if it is not defined) and sets the "int64" type (if it is not set already)
This flag is set when building 464.h264ref on Windows systems.
Pass the command to the C/C++ pre-processor.
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.
This option tells the compiler to perform a conditional check in a vectorized loop.
This checking avoids unnecessary stores and may improve performance.
-Qvec-guard-write- disables this feature. (default)
set the stack reserve amount specified to the linker
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.
Enable C++ Exception Handling and RTTI
This option has the same effect as specifying /GX /GR.
set the stack reserve amount specified to the linker
32-bit MicroQuill SmartHeap Library 8.0 for Windows available from http://www.microquill.com/
Enable SmartHeap library usage by forcing the linker to ignore multiple definitions
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
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.
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 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).
set the stack reserve amount specified to the linker
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
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.
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).
set the stack reserve amount specified to the linker
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
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.
set the stack reserve amount specified to the linker
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
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.
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.
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
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 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.
set the stack reserve amount specified to the linker
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
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.
Tells the compiler the maximum number of times to unroll loops.
If you do not specify n, the optimizer determines how many times loops can be unrolled.
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 tells the compiler to use aggressive multi-versioning to check for pointer aliasing and scalar replacement.
set the stack reserve amount specified to the linker
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
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.
Tells the compiler the maximum number of times to unroll loops.
If you do not specify n, the optimizer determines how many times loops can be unrolled.
set the stack reserve amount specified to the linker
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.
Tells the compiler the maximum number of times to unroll loops.
If you do not specify n, the optimizer determines how many times loops can be unrolled.
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 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).
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 tells the auto-parallelizer to generate multithreaded code for loops
that can be safely executed in parallel.
To use this option, you must also specify option O2 or O3.
This option generates code to perform run-time checks for loops
that have symbolic loop bounds.
If the granularity of a loop is greater than the parallelization threshold,
the loop will be executed in parallel.
If you do not specify this option, the compiler may not parallelize loops with
symbolic loop bounds if the compile-time granularity estimation of a loop can not
ensure it is beneficial to parallelize the loop.
-Qpar-runtime-control - disables this feature. (default)
set the stack reserve amount specified to the linker
32-bit MicroQuill SmartHeap Library 8.0 for Windows available from http://www.microquill.com/
This library is the thread-safe version.
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
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.
Tells the compiler the maximum number of times to unroll loops.
If you do not specify n, the optimizer determines how many times loops can be unrolled.
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.
set the stack reserve amount specified to the linker
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
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.
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.
Method used for partitioning. Possible values are:
routine: Creates a single region for each routine.
block: Partitions each routine into one region per basic block.
trace: Partitions each routine into one region per trace.
region: Partitions each routine into one region per loop.
default: The compiler determines which method is used for partitioning.
This option selects the method that the register allocator uses to partition each routine into regions.
When setting default is in effect, the compiler attempts to optimize the tradeoff between compile-time
performance and generated code performance.
This option is only relevant when optimizations are enabled (O1 or higher).
Enable C++ Exception Handling and RTTI
This option has the same effect as specifying /GX /GR.
set the stack reserve amount specified to the linker
32-bit MicroQuill SmartHeap Library 8.0 for Windows available from http://www.microquill.com/
Enable SmartHeap library usage by forcing the linker to ignore multiple definitions
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
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.
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.
Method used for partitioning. Possible values are:
routine: Creates a single region for each routine.
block: Partitions each routine into one region per basic block.
trace: Partitions each routine into one region per trace.
region: Partitions each routine into one region per loop.
default: The compiler determines which method is used for partitioning.
This option selects the method that the register allocator uses to partition each routine into regions.
When setting default is in effect, the compiler attempts to optimize the tradeoff between compile-time
performance and generated code performance.
This option is only relevant when optimizations are enabled (O1 or higher).
Enable C++ Exception Handling and RTTI
This option has the same effect as specifying /GX /GR.
set the stack reserve amount specified to the linker
32-bit MicroQuill SmartHeap Library 8.0 for Windows available from http://www.microquill.com/
Enable SmartHeap library usage by forcing the linker to ignore multiple definitions
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
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.
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.
Enable C++ Exception Handling and RTTI
This option has the same effect as specifying /GX /GR.
set the stack reserve amount specified to the linker
32-bit MicroQuill SmartHeap Library 8.0 for Windows available from http://www.microquill.com/
Enable SmartHeap library usage by forcing the linker to ignore multiple definitions
This allows alloca to be set to the compiler's preferred alloca by SPEC rules.
This allows alloca to be set to the compiler's preferred alloca by SPEC rules.
This section contains descriptions of flags that were included implicitly by other flags, but which do not have a permanent home at SPEC.
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 enables read only string-pooling optimization.
This option enables read/write string-pooling optimization.
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.
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.
Disables inline expansion of all intrinsic functions.
This option disables stack-checking for routines with 4096 bytes of local variables and compiler temporaries.
Allows use of EBP as a general-purpose register in optimizations.
This option tells the compiler to separate functions into COMDATs for the linker.
This option enables most speed optimizations, but disables some that increase code size for a small speed benefit.
This option enables global optimizations.
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
Tells the compiler the maximum number of times to unroll loops.
If you do not specify n, the optimizer determines how many times loops can be unrolled.
Disables conformance to the ANSI C and IEEE 754 standards for floating-point arithmetic.
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
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.
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 C++ exception handling.
Enables C++ Run Time Type Information (RTTI).
Flag description origin markings:
|
Indicates that the flag description came from the user flags file. |
![[suite]](http://www.spec.org/auto/cpu2006/flags/suite.png) |
Indicates that the flag description came from the suite-wide flags file. |
|
Indicates that the flag description came from a per-benchmark flags file. |
For questions about the meanings of these flags, please contact the tester.
For other inquiries, please contact webmaster@spec.org
Copyright 2006-2014 Standard Performance Evaluation Corporation
Tested with SPEC CPU2006 v1.0.
Report generated on Tue Jul 22 17:08:18 2014 by SPEC CPU2006 flags formatter v6906.