SPEC CPU2006 Flag Description for the Linux Intel(R) C++ Compiler 10.0 for EM64T-based applications and Intel(R) Fortran Compiler 10.0 for EM64T-based applications

optimize for speed, but disable some optimizations which increase code size for a small speed benefit. Includes inline expansion except for intrinsic functions, global optimizations, string pooling optimizations. On Linux platforms, -O1 sets the following:

-unroll0, -fno-builtin -mno-ieee-fp -fomit-frame-pointer -ffunction-sections

This is the default level of optimization. Optimizes for speed. The -O2 option includes O1 optimizations and in addition enables inlining of intrinsics and more speed optimizations.

Builds on -01 and -02 optimizations by enabling high-level optimization. This level does not guarantee higher performance unless loop and memory access transformation take place. In conjunction with -axK/-xK and -axW/-xW, this switch causes the compiler to perform more aggressive data dependency analysis than for -O2. This may result in longer compilation times. On Linux platforms, -O3 sets the following:

-fp

Enable use of ANSI aliasing rules in optimizations.

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.

Tells the compiler not to assume aliasing in the program (DEFAULT = -falias).

enable single-file IP optimizations (within files, same as -Ob2)

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

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)

-ipo (enables interprocedural optimizations across files)

-xT  (generate code specialized for Intel(R) Core(TM)2 Duo processors, Intel(R) Core(TM)2 Quad processors and Intel(R) Xeon(R) processors with SSSE3)

-no-prec-div (disable -prec-div) where -prec-div improves precision of FP divides (some speed impact)

-static (statically link libraries during compilation)

To override one of the options set by /fast, specify that option after the -fast option on the command line. The options set by /fast may change from release to release.

-L -lsmartheap ,
when used as an EXTRA_CLIB or EXTRA_CXXLIB variable, results in linking with MicroQuill's SmartHeap 8.1 (32-bit) library for Linux. This is a library that optimizes calls to new, delete, malloc and free.

The -xN and -xP options target your program to run on Intel Pentium 4 and compatible Intel processors. The resulting code might contain unconditional use of features that are not supported on other processors. Programs, where the function main() is compiled with this option, will detect non compatible processors and generate an error message during execution. This option also enables new optimizations in addition to Intel processor specific optimizations.

These options also enable advanced data layout and code restructuring optimizations to improve memory accesses for Intel processors.

Code is optimized for Intel(R) Core(TM)2 Duo processors, Intel(R) Core(TM)2 Quad processors and Intel(R) Xeon(R) processors with SSSE3. 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.

Do not use this option 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.

(disable/enable[default] -Qprec-div[-]) (Windows) [-no]-prec-div (Linux)

-Qprec-dev (Windows) and -prec-div (Linux) improves precision of floating-point divides. It has a slight impact on speed. -Qprec-dev- (Windows) and -no-prec-div (Linux) disables this option and enables optimizations that give slightly less precise results than full IEEE division.

When you specify -Qprec-dev- (Windows) or -no-prec-div (Linux) along 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, do not use -Qprec-dev- (Windows) or -no-prec-div (Linux) which will enable the default -Qprec-dev (Windows) or -prec-div (Linux) and the result is more accurate, with some loss of performance.

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.

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.

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. The default numbers of threads spawned is equal to the number of processors detected in the system where the binary is compiled. Can be changed by setting the environment variable OMP_NUM_THREADS

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, -prof_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 instructs the compiler to analyze the program to determine if there are 64-bit pointers which can be safely shrunk into 32-bit pointers. In order for this option to be effective the compiler must be able to optimize using the -ipo option, and must be able to analyze all library/external calls the program makes. This option imposes the following restrictions on the program:
The program cannot malloc any objects greater than 2**31 bytes in size.
If the program does not satisfy this restriction, unpredictable behavior may occur.

Enables improved floating-point consistency. Floating-point operations are not reordered and the result of each floating-point operation is stored in the target variable rather than being kept in the floating- point processor for use in a subsequent calculation. This is the same as specifying -fltconsistency or -mp.

The default, -mno-ieee-fp, provides better accuracy and run-time per- formance at the expense of less consistent floating-point results.

Enable using EBP as general purpose register.

Separate functions for the linker (COMDAT). Same as -fdata-sections.

Tells the compiler the maximum number of times to unroll loops.

Disables inline expansion of all intrinsic functions.

Disable using EBP as general purpose register.

This option prevents linking with shared libraries. It causes the executable to link all libraries statically.

Enables generation of streaming stores for optimization.

always - Enables generation of streaming stores for optimization. The compiler optimizes under the assumption that the application is memory bound.

auto - compiler decides when streaming stores are used (DEFAULT)

never - disables generation of streaming stores

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.

syntax: -Wl,-z,muldefs

Enable SmartHeap and/or other library usage by forcing the linker to ignore multiple definitions if present

Scalar replacement is not performed during loop transformation.

Enables scalar replacement performed during loop transformation.

For mixed-language benchmarks, tell the compiler to ignore the main routine in Fortran

/opt/intel/fc/10.0.023/bin/ifort invokes the 32-bit Intel Fortran compiler.
Also used to invoke linker for 32-bit programs in Fortran and C/Fortran mixtures.

Invoke the 64-bit Intel Fortran compiler.
Also used to invoke linker for 64-bit programs in Fortran and C/Fortran mixtures.

/opt/intel/cc/10.0.023/bin/icc invokes the 32-bit Intel C compiler.
Also used to invoke linker for 32-bit C programs.

/opt/intel/cce/10.0.023/bin/icc invokes the 64-bit Intel C compiler.
Also used to invoke linker for 64-bit C programs.

/opt/intel/cc/10.0.023/bin/icpc invokes the 32-bit Intel C++ compiler.
Also used to invoke linker for 32-bit C++ programs.

Invoke the 64-bit Intel C compiler.
Also used to invoke linker for C programs.

Invoke the 64-bit Intel C++ compiler.
Also used to invoke linker for C++ programs.

-I/opt/intel/cc/10.0.023/include is the include path of 32-bit Intel C/C++ compiler

-I/opt/intel/cce/10.0.023/include is the include path of 64-bit Intel C/C++ compiler

-L/opt/intel/cc/10.0.023/lib is the library path of 32-bit Intel C/C++ compiler

-L/opt/intel/cce/10.0.023/lib is the library path of 64-bit Intel C/C++ compiler

-I/opt/intel/fc/10.0.023/include is the include path of 32-bit Intel Fortran compiler

-L/opt/intel/fc/10.0.023/lib is the library path of 32-bit Intel Fortran compiler