[Bug c/25227] New: code generation -- unnecessary spill of structure onto stack

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

The following test program spills res onto the stack when the value res.result,
which is already in a register, should be passed in a register to 
foo();

/* compile with: gcc -fomit-frame-pointer -S */
struct rw_res {
        long result;
        long pos_update;
};

struct file {
        long f_pos;
};

struct rw_res vfs_read(long pos);
long foo(long bar);

long sys_read(struct file *file)
{
        struct rw_res res;
        res = vfs_read(file->f_pos);
        return foo(res.result);
}


-- 
           Summary: code generation -- unnecessary spill of structure onto
                    stack
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bcrl at kvack dot org
 GCC build triplet: x86_64-unknown-linux
  GCC host triplet: x86_64-unknown-linux
GCC target triplet: x86_64-unknown-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25227