[Bug target/66474] New: Document the use of %x in powerpc asm statements

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66474

            Bug ID: 66474
           Summary: Document the use of %x in powerpc asm statements
           Product: gcc
           Version: 5.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: meissner at gcc dot gnu.org
  Target Milestone: ---
              Host: powerpc64-unknown-linux-gnu
            Target: powerpc64-unknown-linux-gnu
             Build: powerpc64-unknown-linux-gnu

A user that was trying to use PowerPC VSX instructions reported that we never
documented that you need to use %x<n> in PowerPC asm statements if the register
could be a VSX register (as opposed to traditional FPR or Altivec register).