re PR target/47025 (Dead stores in variadic functions not eliminated)

2011-09-06  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/47025
	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): BUILT_IN_VA_END
	uses nothing.
	(call_may_clobber_ref_p_1): BUILT_IN_VA_END is a barrier like
	BUILT_IN_FREE.
	(stmt_kills_ref_p_1): BUILT_IN_VA_END kills what its argument
	definitely points to.
	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
	BUILT_IN_VA_START doesn't let its va_list argument escape.
	* tree-ssa-dce.c (propagate_necessity): BUILT_IN_VA_END does
	not make any previous stores necessary.

From-SVN: r178601

gcc/ChangeLog

+2011-09-06  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/47025
+	* tree-ssa-alias.c (ref_maybe_used_by_call_p_1): BUILT_IN_VA_END
+	uses nothing.
+	(call_may_clobber_ref_p_1): BUILT_IN_VA_END is a barrier like
+	BUILT_IN_FREE.
+	(stmt_kills_ref_p_1): BUILT_IN_VA_END kills what its argument
+	definitely points to.
+	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
+	BUILT_IN_VA_START doesn't let its va_list argument escape.
+	* tree-ssa-dce.c (propagate_necessity): BUILT_IN_VA_END does
+	not make any previous stores necessary.
+
 2011-09-06  Martin Jambor  <mjambor@suse.cz>
 
 	* ipa-inline.h (struct inline_summary): Move versionable flag...

gcc/tree-ssa-alias.c

@@ -1254,6 +1254,7 @@ ref_maybe_used_by_call_p_1 (gimple call, ao_ref *ref)
 	case BUILT_IN_SINCOSF:
 	case BUILT_IN_SINCOSL:
 	case BUILT_IN_ASSUME_ALIGNED:
+	case BUILT_IN_VA_END:
 	  return false;
 	/* __sync_* builtins and some OpenMP builtins act as threading
 	   barriers.  */
@@ -1518,6 +1519,7 @@ call_may_clobber_ref_p_1 (gimple call, ao_ref *ref)
 	   the call has to serve as a barrier for moving loads and stores
 	   across it.  */
 	case BUILT_IN_FREE:
+	case BUILT_IN_VA_END:
 	  {
 	    tree ptr = gimple_call_arg (call, 0);
 	    return ptr_deref_may_alias_ref_p_1 (ptr, ref);
@@ -1763,10 +1765,23 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref *ref)
 			      / BITS_PER_UNIT)))
 		    return true;
 		}
+	      break;
+	    }
+
+	  case BUILT_IN_VA_END:
+	    {
+	      tree ptr = gimple_call_arg (stmt, 0);
+	      if (TREE_CODE (ptr) == ADDR_EXPR)
+		{
+		  tree base = ao_ref_base (ref);
+		  if (TREE_OPERAND (ptr, 0) == base)
+		    return true;
+		}
+	      break;
 	    }
+
 	  default:;
 	  }
-
     }
   return false;
 }

gcc/tree-ssa-dce.c

@@ -836,6 +836,7 @@ propagate_necessity (struct edge_list *el)
 		      || DECL_FUNCTION_CODE (callee) == BUILT_IN_MALLOC
 		      || DECL_FUNCTION_CODE (callee) == BUILT_IN_CALLOC
 		      || DECL_FUNCTION_CODE (callee) == BUILT_IN_FREE
+		      || DECL_FUNCTION_CODE (callee) == BUILT_IN_VA_END
 		      || DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA
 		      || DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_SAVE
 		      || DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE

gcc/tree-ssa-structalias.c

@@ -4187,27 +4187,32 @@ find_func_aliases_for_builtin_call (gimple t)
 	 mode as well.  */
       case BUILT_IN_VA_START:
 	{
+	  tree valist = gimple_call_arg (t, 0);
+	  struct constraint_expr rhs, *lhsp;
+	  unsigned i;
+	  get_constraint_for (valist, &lhsc);
+	  do_deref (&lhsc);
+	  /* The va_list gets access to pointers in variadic
+	     arguments.  Which we know in the case of IPA analysis
+	     and otherwise are just all nonlocal variables.  */
 	  if (in_ipa_mode)
 	    {
-	      tree valist = gimple_call_arg (t, 0);
-	      struct constraint_expr rhs, *lhsp;
-	      unsigned i;
-	      /* The va_list gets access to pointers in variadic
-		 arguments.  */
 	      fi = lookup_vi_for_tree (cfun->decl);
-	      gcc_assert (fi != NULL);
-	      get_constraint_for (valist, &lhsc);
-	      do_deref (&lhsc);
 	      rhs = get_function_part_constraint (fi, ~0);
 	      rhs.type = ADDRESSOF;
-	      FOR_EACH_VEC_ELT (ce_s, lhsc, i, lhsp)
-		  process_constraint (new_constraint (*lhsp, rhs));
-	      VEC_free (ce_s, heap, lhsc);
-	      /* va_list is clobbered.  */
-	      make_constraint_to (get_call_clobber_vi (t)->id, valist);
-	      return true;
 	    }
-	  break;
+	  else
+	    {
+	      rhs.var = nonlocal_id;
+	      rhs.type = ADDRESSOF;
+	      rhs.offset = 0;
+	    }
+	  FOR_EACH_VEC_ELT (ce_s, lhsc, i, lhsp)
+	    process_constraint (new_constraint (*lhsp, rhs));
+	  VEC_free (ce_s, heap, lhsc);
+	  /* va_list is clobbered.  */
+	  make_constraint_to (get_call_clobber_vi (t)->id, valist);
+	  return true;
 	}
       /* va_end doesn't have any effect that matters.  */
       case BUILT_IN_VA_END: