[PATCH] Fix PR38908, another bogus uninitialized warning

[Richard Guenther <rguenther at suse dot de>]

Fixed by not warning for uninitialized aggregate uses in call
arguments.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2009-01-27  Richard Guenther  <rguenther@suse.de>

	PR middle-end/38908
	* tree-ssa.c (warn_uninitialized_var): Do not warn for seemingly
	uninitialized aggregate uses in call arguments.

	* g++.dg/warn/Wuninitialized-2.C: New testcase.

Index: gcc/tree-ssa.c
===================================================================
*** gcc/tree-ssa.c	(revision 143699)
--- gcc/tree-ssa.c	(working copy)
*************** warn_uninitialized_var (tree *tp, int *w
*** 1496,1504 ****
              || !gimple_aliases_computed_p (cfun))
  	  return NULL_TREE;
  
  	vuse = SINGLE_SSA_USE_OPERAND (data->stmt, SSA_OP_VUSE);
  	if (vuse == NULL_USE_OPERAND_P)
! 	    return NULL_TREE;
  
  	op = USE_FROM_PTR (vuse);
  	if (t != SSA_NAME_VAR (op) 
--- 1496,1508 ----
              || !gimple_aliases_computed_p (cfun))
  	  return NULL_TREE;
  
+ 	/* If the load happens as part of a call do not warn about it.  */
+ 	if (is_gimple_call (data->stmt))
+ 	  return NULL_TREE;
+ 
  	vuse = SINGLE_SSA_USE_OPERAND (data->stmt, SSA_OP_VUSE);
  	if (vuse == NULL_USE_OPERAND_P)
! 	  return NULL_TREE;
  
  	op = USE_FROM_PTR (vuse);
  	if (t != SSA_NAME_VAR (op) 
Index: gcc/testsuite/g++.dg/warn/Wuninitialized-2.C
===================================================================
*** gcc/testsuite/g++.dg/warn/Wuninitialized-2.C	(revision 0)
--- gcc/testsuite/g++.dg/warn/Wuninitialized-2.C	(revision 0)
***************
*** 0 ****
--- 1,53 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -Wuninitialized" } */
+ 
+ struct S8 { template<typename T> S8(T) { } };
+ 
+ template<typename T> struct S10;
+ template<typename T> struct S10<T()> { typedef T S12; typedef S8 S1(); };
+ 
+ template<typename T> struct S3 { };
+ template<typename T> struct S11 { S11(S3<T>); };
+ 
+ struct S2
+ {
+   template<typename T> operator S11<T>() { return S11<T>(S5<T>()); }
+   template<typename T> struct S5:public S3<T>
+   {
+     virtual typename S10<T>::S12 S13() {
+       return 0;
+     }
+   };
+ };
+ 
+ template<typename T> S11<T> S6(S3<T>) { return S11<T>(S3<T>()); }
+ template<typename S12> struct S7 { typedef S12 S15(); };
+ 
+ struct S4
+ {
+   template<typename T> operator S11<T>()
+   {
+     struct S14:public S3<T>
+     { 
+       S14(S2 x):S11_(x) { }
+       S11<typename S7<typename S10<T>::S12>::S15> S11_;
+     };
+     return S6(S14(S11_));
+   }
+   S2 S11_;
+ };
+ 
+ struct S9
+ {
+   template<typename F> operator S11<F>() { return S11<F>(S14<F>(S11_)); }
+   template<typename F> struct S14:public S3<F>
+   {
+     S14(S4 x):S11_(x) { }
+     S11<typename S10<F>::S1> S11_;
+   };
+   S4 S11_;
+ };
+ 
+ void S15(S11<void()>);
+ void S16() { S9 x; S15(x); }
+