Commits on Feb 22, 2018

1. Optimize true/false conditions when coding if-statements …

   We already had some code which "optimized" some if-statements
   with one or two conditions, where one or both were constant equal
   to `true` or `false`. We skipped branches whose condition was
   always `false`. However, we did not use the `IntrIgnoring` mechanism
   for that. Thus, such code would still trigger warnings if it contained
   undefined globals, e.g.
   
       gap> f:=function()  if false then undefined_global(); fi; end;;
       Syntax warning: Unbound global variable
       f:=function()  if false then undefined_global(); fi; end;;
                                                    ^
   
   This can be viewed as a feature, or as a bug, depending on view point.
   A reason to consider it a "bug" (or at least an undesirable feature)
   is when using global constants to only conditionally execute code, such
   as this:
   
       if IsHPCGAP then
           UNLOCK(lock);
       fi;
   
   This code is optimized away in regular GAP, but still triggers a warning
   during parsing.
   
   With this commit, we change how we deal with true/false conditions in
   if-statements, by making use of the `IntrIgnoring` mechanism. This avoids
   the warnings about globals in the examples above. It also has the side
   effect of being "better" at optimizing away branches of an if-statement
   which can never be executed.

   

   fingolfin committed Feb 22, 2018
   Configuration menu

   • View commit details
   • Copy full SHA for a06694c
   • Browse repository at this point

   Copy the full SHA

   a06694c View commit details

   Browse the repository at this point in the history