[Bug rtl-optimization/6833] gcse generates wrong code with regard to global register variables

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

------- Additional Comments From reichelt at gcc dot gnu dot org  2004-06-15 15:01 -------
Hi Bruno,

you wrote:

> Still, could you add my testcase to the testsuite? Global register
> variables are not used by many programs, but GNU clisp relies on them
> very much. I'd like to not see this bug appear again.

Well, your testcase can be reduced to the following:

=======================================
register int* p __asm__("%ebx");

void foo()
{
    --p;
}

int main()
{
    int a[3] = { 0, 0, 0 };

    p = a+2;
    do *(p-1)=1; while (!p);
    foo();

    return *(p-1);
}
=======================================

The result should be zero, but gcc 3.1 returns something different :-(
As you noticed, the bug disappeared in gcc 3.2.

In fact, this PR is a duplicate of PR 6722, which got fixed by RTH
for gcc 3.2. He also added a similar testcase to the testsuite
which should cover this kind of problem.

So I'm reopening this PR...


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |reichelt at gcc dot gnu dot
                   |                            |org
             Status|RESOLVED                    |REOPENED
          Component|middle-end                  |rtl-optimization
      Known to fail|                            |3.1
      Known to work|                            |3.2
         Resolution|FIXED                       |
   Target Milestone|---                         |3.1.x/3.2.x


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=6833