[Bug target/77934] New: pattern for mtvsrdd needs to use b constraint not r

[acsawdey at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77934

            Bug ID: 77934
           Summary: pattern for mtvsrdd needs to use b constraint not r
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: acsawdey at gcc dot gnu.org
          Reporter: acsawdey at gcc dot gnu.org
                CC: wschmidt at gcc dot gnu.org
  Target Milestone: ---
            Target: powerpc64le-linux

gcc 7 trunk generates incorrect code in spec 2k6 403.gcc where it tries to use
r0 as the first input register to mtvsrdd and results in storing a null pointer
instead of the desired value.