Backport https://golang.org/cl/46511 from gc trunk, as it may fix a
    bug reported for gccgo running on MIPS
    (https://groups.google.com/d/msg/golang-dev/sDg-t1_DPw0/-AJmLxgPBQAJ).
    
    Reviewed-on: https://go-review.googlesource.com/46571

From-SVN: r249599