[Bug target/86160] New: Implement isinf on PowerPC

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86160

            Bug ID: 86160
           Summary: Implement isinf on PowerPC
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: meissner at gcc dot gnu.org
  Target Milestone: ---

PowerPC with the VSX instruction set has the xststdcdp instruction that can be
used to test if a value is infinity (and the xststdcqp instruction for IEEE
128-bit).  We should use this for the IEEE math builtins like __builtin_isinf.