SPEC Flag Description for the Clang/Flang Compiler

Disregard strict standards compliance. -Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard-compliant programs. It turns on -ffast-math and the Fortran-specific -fno-protect-parens and -fstack-arrays.

Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran. When -fopenmp is specified, the compiler generates parallel code according to the OpenMP Application Program Interface v4.0 . This option implies -pthread, and thus is only supported on targets that have support for -pthread. -fopenmp implies -fopenmp-simd.

Enable handling of OpenMP's SIMD directives with "#pragma omp" in C/C++ and "!$omp" in Fortran. Other OpenMP directives are ignored.

Generate code for 32-bit or 64-bit ABI.

Generate instructions for Intel's Ivy Bridge CPU. In contrast to -mtune=cpu-type, which merely tunes the generated code for the specified cpu-type, -march=cpu-type allows clang to generate code that may not run at all on processors other than the one indicated. Specifying -march=cpu-type implies -mtune=cpu-type.

Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AES, PCLMUL, FSGSBASE, RDRND and F16C instruction set support.

Enable all instruction subsets supported by the local machine. In contrast to -mtune=cpu-type, which merely tunes the generated code for the specified cpu-type, -march=cpu-type allows clang to generate code that may not run at all on processors other than the one indicated. Specifying -march=cpu-type implies -mtune=cpu-type.

specifies signed char characters. The compiler treats "plain" char declarations as signed char.

Disable range checking on results of simplification of constant expressions during compilation. For example, GNU Fortran will give an error at compile time when simplifying "a = 1. / 0". With this option, no error will be given and "a" will be assigned the value "+Infinity". If an expression evaluates to a value outside of the relevant range of ["-HUGE()":"HUGE()"], then the expression will be replaced by "-Inf" or "+Inf" as appropriate. Similarly, "DATA i/Z'FFFFFFFF'/" will result in an integer overflow on most systems, but with -fno-range-check the value will "wrap around" and "i" will be initialized to -1 instead.

Specify the layout used by the source file is free form.

-mcmodel= use a specific memory model to generate code and store data small - Restricts code and data to the first 2GB of address space (DEFAULT) medium - Restricts code to the first 2GB; it places no memory restriction on data large - Places no memory restriction on code or data

enable language support for , as described below c99 enable C99 support for C programs c++0x enable preliminary support for some C++0x features

Assume free-format source.

Invoke the Clang C compiler

Invoke the Clang C++ compiler

Invoke the Flang Fortran compiler