[Bug middle-end/21417] New: Missed jump threading opportunity on trees

[steven at gcc dot gnu dot org]

Consider the following test case (t.c): 
-------------------------------- 
struct tree_common 
{ 
  int code; 
}; 
union tree_node 
{ 
  struct tree_common common; 
}; 
typedef union tree_node *tree; 
 
extern tree test (tree, int, int); 
extern tree foo (void); 
extern void abort (void) __attribute__ ((__noreturn__)); 
 
tree 
test (tree expr, int t, int D17630) 
{ 
  int __i; 
 
L0: 
  if (expr->common.code != 142) goto L23; else goto L2; 
 
L2: 
  __i = 0; 
  goto L10; 
 
L10: 
  __i = __i + 1; 
  if (D17630 != __i) goto L8; else goto L19; 
 
L8: 
  if (t) goto L15; else goto L10; 
 
L15: 
  expr = foo (); 
  if (expr->common.code != 142) goto L23; else goto L0; 
 
L19: 
  abort (); 
 
L23: 
  return expr; 
} 
-------------------------------- 
 
$ ./cc1 -quiet -O3 -dG --param max-cse-path-length=1 -fdump-tree-vars t.c 
$ grep "Bypass edge" t.c.07.bypass 
Bypass edge from 5->1 to 2 
# ./cc1 --version 
GNU C version 4.1.0 20050506 (experimental) (x86_64-unknown-linux-gnu) 
        compiled by GNU C version 4.1.0 20050506 (experimental). 
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072

-- 
           Summary: Missed jump threading opportunity on trees
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, TREE
          Severity: normal
          Priority: P2
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: steven at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org,law at redhat dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21417