[PATCH] Fix PR51070, loop distribution and memset generation

[Richard Guenther <rguenther at suse dot de>]

This fixes PR51070 where we repace the partition

<bb 5>:
  # g_224.0_23 = PHI <g_224.1_10(7), g_224.0_22(4)>
  D.2957_3 = g_92[g_224.0_23];
  g_92[g_224.0_23] = 0;
  g_224.1_10 = g_224.0_23 + 1;
  if (g_224.1_10 != 0)
    goto <bb 7>;
  else
    goto <bb 6>;

<bb 6>:
  # g_95_I_lsm.15_29 = PHI <D.2957_3(5)>
  g_95[0] = g_95_I_lsm.15_29;
  g_224 = 0;
  goto <bb 3>;

<bb 7>:
  goto <bb 5>;

with a memset, throwing away the statement that loads D.2957_3
and thus causing an SSA name on the freelist to remain in
the PHI node in BB6.

We obviously cannot create a memset for such a partition.

Bootstrap and regtest pending on x86_64-unknown-linux-gnu.

Richard.

2011-11-10  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/51070
	* tree-loop-distribution.c (generate_builtin): Do not replace
	the loop with a builtin if the partition contains statements which
	results are used outside of the loop.
	(pass_loop_distribution): Verify and collect.

	* gcc.dg/torture/pr51070.c: New testcase.

Index: gcc/tree-loop-distribution.c
===================================================================
*** gcc/tree-loop-distribution.c	(revision 181252)
--- gcc/tree-loop-distribution.c	(working copy)
*************** static bitmap remaining_stmts;
*** 63,68 ****
--- 63,110 ----
     predecessor a node that writes to memory.  */
  static bitmap upstream_mem_writes;
  
+ /* Returns true when DEF is an SSA_NAME defined in LOOP and used after
+    the LOOP.  */
+ 
+ static bool
+ ssa_name_has_uses_outside_loop_p (tree def, loop_p loop)
+ {
+   imm_use_iterator imm_iter;
+   use_operand_p use_p;
+ 
+   FOR_EACH_IMM_USE_FAST (use_p, imm_iter, def)
+     if (loop != loop_containing_stmt (USE_STMT (use_p)))
+       return true;
+ 
+   return false;
+ }
+ 
+ /* Returns true when STMT defines a scalar variable used after the
+    loop.  */
+ 
+ static bool
+ stmt_has_scalar_dependences_outside_loop (gimple stmt)
+ {
+   tree name;
+ 
+   switch (gimple_code (stmt))
+     {
+     case GIMPLE_ASSIGN:
+       name = gimple_assign_lhs (stmt);
+       break;
+ 
+     case GIMPLE_PHI:
+       name = gimple_phi_result (stmt);
+       break;
+ 
+     default:
+       return false;
+     }
+ 
+   return TREE_CODE (name) == SSA_NAME
+     && ssa_name_has_uses_outside_loop_p (name, loop_containing_stmt (stmt));
+ }
+ 
  /* Update the PHI nodes of NEW_LOOP.  NEW_LOOP is a duplicate of
     ORIG_LOOP.  */
  
*************** generate_builtin (struct loop *loop, bit
*** 330,339 ****
  	{
  	  gimple stmt = gsi_stmt (bsi);
  
! 	  if (gimple_code (stmt) != GIMPLE_LABEL
! 	      && !is_gimple_debug (stmt)
! 	      && bitmap_bit_p (partition, x++)
! 	      && is_gimple_assign (stmt)
  	      && !is_gimple_reg (gimple_assign_lhs (stmt)))
  	    {
  	      /* Don't generate the builtins when there are more than
--- 372,389 ----
  	{
  	  gimple stmt = gsi_stmt (bsi);
  
! 	  if (gimple_code (stmt) == GIMPLE_LABEL
! 	      || is_gimple_debug (stmt))
! 	    continue;
! 
! 	  if (!bitmap_bit_p (partition, x++))
! 	    continue;
! 
! 	  /* If the stmt has uses outside of the loop fail.  */
! 	  if (stmt_has_scalar_dependences_outside_loop (stmt))
! 	    goto end;
! 
! 	  if (is_gimple_assign (stmt)
  	      && !is_gimple_reg (gimple_assign_lhs (stmt)))
  	    {
  	      /* Don't generate the builtins when there are more than
*************** fuse_partitions_with_similar_memory_acce
*** 824,871 ****
  	  }
  }
  
- /* Returns true when DEF is an SSA_NAME defined in LOOP and used after
-    the LOOP.  */
- 
- static bool
- ssa_name_has_uses_outside_loop_p (tree def, loop_p loop)
- {
-   imm_use_iterator imm_iter;
-   use_operand_p use_p;
- 
-   FOR_EACH_IMM_USE_FAST (use_p, imm_iter, def)
-     if (loop != loop_containing_stmt (USE_STMT (use_p)))
-       return true;
- 
-   return false;
- }
- 
- /* Returns true when STMT defines a scalar variable used after the
-    loop.  */
- 
- static bool
- stmt_has_scalar_dependences_outside_loop (gimple stmt)
- {
-   tree name;
- 
-   switch (gimple_code (stmt))
-     {
-     case GIMPLE_ASSIGN:
-       name = gimple_assign_lhs (stmt);
-       break;
- 
-     case GIMPLE_PHI:
-       name = gimple_phi_result (stmt);
-       break;
- 
-     default:
-       return false;
-     }
- 
-   return TREE_CODE (name) == SSA_NAME
-     && ssa_name_has_uses_outside_loop_p (name, loop_containing_stmt (stmt));
- }
- 
  /* Returns true when STMT will be code generated in a partition of RDG
     different than PART and that will not be code generated as a
     builtin.  */
--- 874,879 ----
*************** struct gimple_opt_pass pass_loop_distrib
*** 1311,1316 ****
    0,				/* properties_provided */
    0,				/* properties_destroyed */
    0,				/* todo_flags_start */
!   0                             /* todo_flags_finish */
   }
  };
--- 1319,1325 ----
    0,				/* properties_provided */
    0,				/* properties_destroyed */
    0,				/* todo_flags_start */
!   TODO_ggc_collect
!   | TODO_verify_ssa             /* todo_flags_finish */
   }
  };
Index: gcc/testsuite/gcc.dg/torture/pr51070.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr51070.c	(revision 0)
--- gcc/testsuite/gcc.dg/torture/pr51070.c	(revision 0)
***************
*** 0 ****
--- 1,34 ----
+ /* { dg-do compile } */
+ 
+ int
+ func_4 (int si1, int si2)
+ {
+   return si1;
+ }
+ 
+ int
+ func_14 (int left, int right)
+ {
+   return 1;
+ }
+ 
+ int
+ func_37 (int left, int right)
+ {
+   return left;
+ }
+ 
+ int g_92[1024];
+ int g_95[1024];
+ int g_224;
+ int g_352[1024];
+ int
+ func_9 ()
+ {
+   for (; g_224; g_224 += 1)
+     {
+       g_95[0] = func_4 (func_37 (g_92[g_224], 0), 0);
+       g_92[g_224] = 0, g_352[g_224] = func_14 (0, 0);
+     }
+   return 0;
+ }