A loop change is also proposed to increase efficiency.

May I suggest you to split this into two patches (when committing at least). We shouldn't mix a bug-fix with a performance improvement unless the performance improvement is needed in a direct relation with the bugfix.

Hi @Germano Cavalcante (mano-wii) there are a few warnings with the patch:

//source/blender/editors/transform/transform.c: In function ‘calcEdgeSlide_mval_range’:
//source/blender/editors/transform/transform.c:6925:11: warning: unused variable ‘e’ [-Wunused-variable]
   BMEdge *e;
           ^
//source/blender/editors/transform/transform.c:6924:10: warning: unused variable ‘iter’ [-Wunused-variable]
   BMIter iter;
          ^~~~
//source/blender/editors/transform/transform.c:6912:10: warning: unused variable ‘bm’ [-Wunused-variable]
   BMesh *bm = em->bm;
          ^~
//source/blender/editors/transform/transform.c:6904:49: warning: unused parameter ‘sv_table’ [-Wunused-parameter]
                                      const int *sv_table,
                                                 ^~~~~~~~

Thanks for taking a look.
A bit annoying to find these warnings in the middle of the other 180 msvc19's warnings (but you can hide by group so it's not a justification).

I can separate the optimization into another commit.
(Without it the code runs at least twice per vertex and edge calling even three raycast per edge!)

I can separate the optimization into another commit.

This helps the review as well, since the patch becomes smaller.

Also note that your patch will likely need a manual merge conflict fix because of: 5ca302cb0cb40506e1f8a5f22e9baa3738ab4a58