[Bug target/86314] [7/8/9 Regression] GCC 7.x and 8.x zero out "eax" before using "rax" in "lock bts"

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86314

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
             Status|UNCONFIRMED                 |NEW
      Known to work|                            |6.4.1
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2018-06-26
     Ever confirmed|0                           |1
            Summary|GCC 7.x and 8.x zero out    |[7/8/9 Regression] GCC 7.x
                   |"eax" before using "rax" in |and 8.x zero out "eax"
                   |"lock bts"                  |before using "rax" in "lock
                   |                            |bts"
   Target Milestone|---                         |7.4
      Known to fail|                            |7.3.1, 8.1.1, 9.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  GCC 6 code generation is wastly different but doesn't exhibit this
issue.