[Bug tree-optimization/38691] New: missed optimization with const pointers

[tkoenig at gcc dot gnu dot org]

This is one possible C equivalent of PR 23169, a Fortran PR.

$ cat foo.c
void bar(const int *, const int *);

int foo(const int *b, const int *c)
{
    int d,e;
    d = *b;
    e = *c;

    bar(b, c);
    return (d- *b) + (e - *c);
}
$ gcc -O3 -fdump-tree-optimized -S foo.c
$ cat foo.c.123t.optimized

;; Function foo (foo)

Analyzing Edge Insertions.
foo (const int * b, const int * c)
{
  int e;
  int d;

<bb 2>:
  d = *b;
  e = *c;
  bar (b, c);
  return ((e - *b) + d) - *c;

}

Without the call to bar, the function is optimized
to "return 0".  This should be possible even with the
call to bar, because all pointers in sight are marked const.


-- 
           Summary: missed optimization with const pointers
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: alias
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tkoenig at gcc dot gnu dot org
OtherBugsDependingO 23169
             nThis:


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38691