SPEC CPU2006 Flag Description for the Linux Intel(R) C++ Compiler 9.1 for EM64T-based applications and Intel(R) Fortran Compiler 9.1 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 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)

-xP  (generate code specialized for Intel Pentium 4 processor and compatible Intel processors with Streaming SIMD Extensions 3)

-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.

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.

Allows the compiler to perform optimizations in FP divides that may impact precision while improving speed.

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, -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.

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

Invoke the Intel C compiler for EM64T based applications

Invoke the Intel C++ compiler for EM64T based applications

Invoke the Intel Fortran compiler for EM64T based applications