[Bug middle-end/77926] New: Add __builtin_iszero

[jsm28 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77926

            Bug ID: 77926
           Summary: Add __builtin_iszero
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jsm28 at gcc dot gnu.org
  Target Milestone: ---

TS 18661-1 defines an iszero type-generic floating-point classification macro. 
GCC should have a corresponding type-generic built-in function
__builtin_iszero.  As with other such type-generic classification functions it
should be included in the cases in c-typeck.c:convert_arguments that remove
excess precision.  (In the absence of signaling NaNs this can just be a
comparison against 0.)