[Bug ada/37599] renamed volatile variables are not treated as volatile

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

------- Comment #1 from sam at gcc dot gnu dot org  2008-09-20 20:08 -------
Rolf,

could you include the problematic assembler code? On i686-pc-linux-gnu, it
looks like it generates the expected code except for the bogus extra access
that I submitted as a separate bug in PR ada/37602:

_ada_b:
        movl    a__var, %edx
        movzbl  (%edx), %eax         <=== extra access
        movzbl  (%edx), %eax            <=== volatile read through renaming
        orl     $1, %eax
        movb    %al, (%edx)             <=== volatile write through renaming
        movl    a__var, %edx         <=== looks like a useless assignment
        movzbl  (%edx), %eax            <=== volatile read
        orl     $1, %eax
        movb    %al, (%edx)             <=== volatile write
        ret

Adding an extra "renamed := renamed or 2;" shows that reads and writes are not
aggregated, as expected for a volatile variable.

I will file a separate report for the missed optimization.


-- 

sam at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gcc dot gnu dot org
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37599