------------------------------------------------------ ION Computer Systems SPEC CPU2000 Flags Descriptions Intel C/C++/FORTRAN Compilers Version 8.0 For Config Files: 8ion_xeon.322.cfg 8ion_xeon.321.cfg ------------------------------------------------------ ------------------------------------------------------ General Options (C/C++/FORTRAN) ------------------------------------------------------ -O{1|2|3} Optimization-level options: 1: optimize for speed, but disable some optimizations that increase code size for a small speed benefit. Includes inline expansion for intrinsic functions, global optimizations, string pooling optimizations. 2: optimizes for speed (DEFAULT). The -O2 option includes O1 optimizations and in addition enables inlining of intrinsics and more speed optimizations. 3: 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 -QaxK/-QxK and QaxW/QxW, this switch causes the compiler to perform more aggressive data dependency analysis than for -O2. This may result in longer compilation times. -Oa[-] Assume [do not assume] no aliasing in program. -ax{K|W|N|P} (IA-32 only) Generates specialized code for processor-specific codes (see -Qx) while also generating generic IA-32 code. -x{K|W|N|P} (IA-32 only) Generates specialized code for processor specific codes: K: Intel Pentium III and compatible Intel processors. W: Intel Pentium 4 and compatible Intel processors. N: Intel Pentium 4 and compatible Intel processors. P: Intel Processors code-named "Prescott". Notes: -x{N|P} and -ax{N|P}: These options also enable advanced data layout and code restructuring optimizations to improve memory accesses for Intel processors. -x{N|P}: Programs, where the function main()is compiled with these options, will detect non-compatible processors and generate an error message during execution. -ip Enable single-file IP optimizations (within files, same as -Ob2). -ipo Enable multi-file IP optimizations (between files). - inline function expansion - interprocedural constant propogation - dead code elimination - propagation of function characteristics - passing arguments in registers - loop-invariant code motion -prof_gen Instrument program for profiling for the first phase of two-phase profile guided optimization. -prof_use 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. -rcd The Intel compiler uses the -Qrcd option to improve the performance of code that requires floating-point-to-integer conversions. The system default floating point rounding mode is round-to-nearest. This means that values are rounded during floating point calculations. However, the C language requires floating point values to be truncated when a conversion to an integer is involved. To do this, the compiler must change the rounding mode to truncation before each floating point-to-integer conversion and change it back afterwards. The -Qrcd option disables the change to truncation of the rounding mode for all floating point calculations, including floating point-to-integer conversions. Turning on this option can improve performance, but floating point conversions to integer may not conform to C semantics. -unroll[n] Specifies the maximum number of times to unroll a loop. Omit n to let the compiler decide whether to perform unrolling or not. Use n = 0 to disable unroller. ------------------------------------------------------ Flags Specific to FORTRAN ------------------------------------------------------ -auto Causes all variables to be allocated on the stack, rather than in local static storage. -prefetch[-] Enable [disable (DEFAULT)] prefetch insertion. The default with -O3 is -prefetch. -scalar_rep[-] Enables (DEFAULT) [disables] scalar replacement performed during loop transformations. ------------------------------------------------------ Miscellaneous ------------------------------------------------------ +FDO PASS1= -prof_gen PASS2= -prof_use Using feedback-directed optimization, a profile is generated on the first pass of compilation and used on the second pass.