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[PATCH] Fix PR44030


We have to be more careful with the NECESSARY flag.

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

Richard.

2010-05-08  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/44030
	* tree-ssa-pre.c (eliminate): Copy NECESSARY flag.  Set
	NECESSARY flag if we propagate from a inserted expression.

	* gcc.c-torture/compile/pr44030.c: New testcase.

Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c	(revision 159171)
--- gcc/tree-ssa-pre.c	(working copy)
*************** eliminate (void)
*** 4351,4356 ****
--- 4351,4357 ----
  	    sprime = fold_convert (TREE_TYPE (res), sprime);
  	  stmt = gimple_build_assign (res, sprime);
  	  SSA_NAME_DEF_STMT (res) = stmt;
+ 	  gimple_set_plf (stmt, NECESSARY, gimple_plf (phi, NECESSARY));
  
  	  gsi2 = gsi_after_labels (b);
  	  gsi_insert_before (&gsi2, stmt, GSI_NEW_STMT);
*************** eliminate (void)
*** 4381,4388 ****
  	  && single_imm_use (lhs, &use_p, &use_stmt)
  	  && may_propagate_copy (USE_FROM_PTR (use_p), rhs))
  	{
! 	  SET_USE (use_p, gimple_assign_rhs1 (stmt));
  	  update_stmt (use_stmt);
  	}
  
        /* If this is a store or a now unused copy, remove it.  */
--- 4382,4392 ----
  	  && single_imm_use (lhs, &use_p, &use_stmt)
  	  && may_propagate_copy (USE_FROM_PTR (use_p), rhs))
  	{
! 	  SET_USE (use_p, rhs);
  	  update_stmt (use_stmt);
+ 	  if (bitmap_bit_p (inserted_exprs, SSA_NAME_VERSION (lhs))
+ 	      && TREE_CODE (rhs) == SSA_NAME)
+ 	    gimple_set_plf (SSA_NAME_DEF_STMT (rhs), NECESSARY, true);
  	}
  
        /* If this is a store or a now unused copy, remove it.  */
Index: gcc/testsuite/gcc.c-torture/compile/pr44030.c
===================================================================
*** gcc/testsuite/gcc.c-torture/compile/pr44030.c	(revision 0)
--- gcc/testsuite/gcc.c-torture/compile/pr44030.c	(revision 0)
***************
*** 0 ****
--- 1,28 ----
+ typedef int int32_t;
+ typedef unsigned int uint32_t;
+ static uint32_t
+ safe_sub_func_uint32_t_u_u (uint32_t ui1, uint32_t ui2)
+ {
+   return ui1 - ui2;
+ }
+ 
+ int32_t l_105[7];
+ 
+ int32_t g_4;
+ int32_t *g_54 = &g_4;
+ int32_t *
+ func (int32_t p_73, int32_t * p_74, int32_t p_75, int32_t * *p_76,
+       int32_t * *p_77)
+ {
+ lbl_110:for (g_4 = 0; g_4; g_4 = 1)
+     {
+     }
+   for (p_75 = -28; p_75; p_75 = safe_sub_func_uint32_t_u_u (p_75, 1))
+     {
+       if (g_4)
+         goto lbl_110;
+       *g_54 = 0;
+     }
+   return &l_105[5];
+ }
+ 


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