[Bug target/70928] New: Load simple float constants via VSX operations on PowerPC

["meissner at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70928

            Bug ID: 70928
           Summary: Load simple float constants via VSX operations on
                    PowerPC
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: meissner at gcc dot gnu.org
  Target Milestone: ---

With Power8 (and to a lesser extent Power7), we can create simple integer
values in VSX registers without doing a load in a few instructions (for example
-16..15 can be loaded with VSPLTIWS and VUPKHSW). If the code wants to use
these simple constants as floating point values, it is probably cheaper to load
the constants as integers and convert them to floating point, rather than
loading the constant from memory.