[PATCH] Fix PR59330

[Richard Biener]

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

Richard.

2013-11-28  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/59330
        * tree-ssa-dce.c (eliminate_unnecessary_stmts): Simplify
        and fix delayed marking of free calls not necessary.

        * gcc.dg/torture/pr59330.c: New testcase.

Index: gcc/tree-ssa-dce.c
===================================================================
*** gcc/tree-ssa-dce.c  (revision 205484)
--- gcc/tree-ssa-dce.c  (working copy)
*************** eliminate_unnecessary_stmts (void)
*** 1191,1216 ****
          stats.total++;
  
          /* We can mark a call to free as not necessary if the
!            defining statement of its argument is an allocation
!            function and that is not necessary itself.  */
!         if (gimple_call_builtin_p (stmt, BUILT_IN_FREE))
            {
              tree ptr = gimple_call_arg (stmt, 0);
!             tree callee2;
!             gimple def_stmt;
!             if (TREE_CODE (ptr) != SSA_NAME)
!               continue;
!             def_stmt = SSA_NAME_DEF_STMT (ptr);
!             if (!is_gimple_call (def_stmt)
!                 || gimple_plf (def_stmt, STMT_NECESSARY))
!               continue;
!             callee2 = gimple_call_fndecl (def_stmt);
!             if (callee2 == NULL_TREE
!                 || DECL_BUILT_IN_CLASS (callee2) != BUILT_IN_NORMAL
!                 || (DECL_FUNCTION_CODE (callee2) != BUILT_IN_MALLOC
!                     && DECL_FUNCTION_CODE (callee2) != BUILT_IN_CALLOC))
!               continue;
!             gimple_set_plf (stmt, STMT_NECESSARY, false);
            }
  
          /* If GSI is not necessary then remove it.  */
--- 1191,1208 ----
          stats.total++;
  
          /* We can mark a call to free as not necessary if the
!            defining statement of its argument is not necessary
!            (and thus is getting removed).  */
!         if (gimple_plf (stmt, STMT_NECESSARY)
!             && gimple_call_builtin_p (stmt, BUILT_IN_FREE))
            {
              tree ptr = gimple_call_arg (stmt, 0);
!             if (TREE_CODE (ptr) == SSA_NAME)
!               {
!                 gimple def_stmt = SSA_NAME_DEF_STMT (ptr);
!                 if (!gimple_plf (def_stmt, STMT_NECESSARY))
!                   gimple_set_plf (stmt, STMT_NECESSARY, false);
!               }
            }
  
          /* If GSI is not necessary then remove it.  */
Index: gcc/testsuite/gcc.dg/torture/pr59330.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr59330.c      (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr59330.c      (working copy)
***************
*** 0 ****
--- 1,17 ----
+ /* { dg-do run } */
+ 
+ void free(void *ptr)
+ {
+ }
+ 
+ void *foo(void)
+ {
+   return 0;
+ }
+ 
+ int main(void)
+ {
+   void *p = foo();
+   free(p);
+   return 0;
+ }