Hi Dmitri, I think the optimization hint docs should be high-level, and the Rpass diagnostics should be used to determine if/why an optimization is not being applied. What do you think about adding this paragraph to the language extensions guide to clarify this?
If an optimization cannot be applied its hints will be ignored. For example, the hint ``vectorize_width(4)`` is ignored if the loop is not proven safe to vectorize. To identify and diagnose optimization issues use `-Rpass`, `-Rpass-missed`, and `-Rpass-analysis` command line options. See the user guide for details. Tyler On Jun 11, 2014, at 8:06 AM, Dmitri Gribenko <[email protected]> wrote: > On Wed, Jun 11, 2014 at 2:20 AM, Tyler Nowicki <[email protected]> wrote: >> Hi, >> >> Here is a patch for the loop hints documentation. I’m not exactly sure if I >> wrote the attribute documentation correctly. If I missed something please >> let me know. > >> +Extensions for loop hint optimizations >> +====================================== >> + >> +The ``#pragma clang loop`` directive is used to specify hints for >> optimizing the >> +subsequent for, while, do-while, or c++11 range-based for loop. The >> directive >> +provides options for controlling vectorization, interleaving, and unrolling. > > This documentation describes syntax and the high-level effect of the > pragma, but it does not explain what are the semantic constraints on > the loop. Users would want to know when it is valid to apply the > pragma, and the documentation does not explain that. > > Dmitri > > -- > main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if > (j){printf("%d\n",i);}}} /*Dmitri Gribenko <[email protected]>*/
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