[Bug tree-optimization/22237] New: [4.0/4.1 Regression] struct copy inlining generates overlapping memcpy

[jsm28 at gcc dot gnu dot org]

The following test should execute successfully (see C99 6.8.6.4#3 and #4: a
return statement is not an assignment so can be used to copy between overlapping
structures - added in C90 TC1 following DR#001).  With 4.0 branch and mainline,
it aborts when compiled at -O3 (maybe other levels as well) because the
assignment via an inline function call has been wrongly optimized to a direct
assignment.  gcc.c-torture/execute/20010124-1.c used to test for such an issue,
but it now all gets optimized away so a more complicated test such as this one
is needed.

extern void abort (void);
extern void exit (int);
struct s { unsigned char a[256]; };
union u { struct { struct s b; int c; } d; struct { int c; struct s b; } e; };
union u v;
union u v0;
struct s *p = &v.d.b;
struct s *q = &v.e.b;

static inline struct s rp (void) { return *p; }
static inline struct s rq (void) { return *q; }
void pq (void) { *p = rq(); }
void qp (void) { *q = rp(); }

void
init (struct s *sp)
{
  int i;
  for (i = 0; i < 256; i++)
    sp->a[i] = i;
}

void
check (struct s *sp)
{
  int i;
  for (i = 0; i < 256; i++)
    if (sp->a[i] != i)
      abort ();
}

int
main (void)
{
  v = v0;
  init (p);
  qp ();
  check (q);
  v = v0;
  init (q);
  pq ();
  check (p);
  exit (0);
}

-- 
           Summary: [4.0/4.1 Regression] struct copy inlining generates
                    overlapping memcpy
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jsm28 at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22237