[Bug middle-end/35361] New: Missing dead store elimination for statics

[xinliangli at gmail dot com]

// David Li

Gcc is solid in performing dead function elimination and dead variable
elimination for statics. It handles cases when a dead variable is referenced
(via initializer) by other dead variables pretty well. The missing
opportunities noticed is that it fails to discover dead stores to static
variables where are never used -- thus missing the dead variable elimination
...

Example 1:

static int s;
static int* p =&s;

int foo()
{
   p = 0;      // Dead, not eliminated
}


Example 2:

static int g = 10;
static int* gp = &g;

int foo()
{
  gp = 0;      // Dead store
  return g;    // should be const proped
}


-- 
           Summary: Missing dead store elimination for statics
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: xinliangli at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35361