The Intel compiler supports the option "-fp-model=(source|double|extended)" which causes the compiler to use a wider type for intermediate floating point calculations. Also supported is a way to embed this effect in the source program with #pragma float_control(source|double|extended). This patch proposes to extend pragma float_control syntax, and also to support a new floating point option via "-ffp-eval-method=(source|double|extended)"
Note that the C floating point working group has proposed nearly identical pragma semantics in http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1974.pdf like this
#pragma STDC FENV_FLT_EVAL_METHOD width
I would like to add support for this also, but it's not in this patch. In the WG14 document, the standard widths are 0,1,2 representing source, double and extended precision. Negative values of width are reserved for the implementation.
The ICL option with description of semantics is at this url, https://software.intel.com/content/www/us/en/develop/documentation/cpp-compiler-developer-guide-and-reference/top/compiler-reference/compiler-options/compiler-option-details/floating-point-options/fp-model-fp.html
Quoting that here for easy reference "source
Rounds intermediate results to source-defined precision.
Rounds intermediate results to 53-bit (double) precision.
Rounds intermediate results to 64-bit (extended) precision."