[Bug regression/23328] New: Improper removal of struct field assignments by optimizer

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

GCC 4.0.0 and later optimize out struct assignments inappropriately when the
struct is used as an input to an asm().  For example, in:

int foo(int a, int b) {
    struct {int a,b} args;
    args.a = a; args.b = b;
    asm("..." : "" : "S" (&args));
}

the args.a and args.b assignments are optimized out (with -O3 at least) despite
the structure being specified as an input to the asm().  See attached files.

-- 
           Summary: Improper removal of struct field assignments by
                    optimizer
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: regression
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gcczilla at achurch dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23328