re PR target/42495 (redundant memory load)

	PR target/42495
	PR middle-end/42574
	* basic-block.h (get_dominated_to_depth): Declare.
	* dominance.c (get_dominated_to_depth): New function, use
	get_all_dominated_blocks as a base.
	(get_all_dominated_blocks): Use get_dominated_to_depth.

	* gcse.c (occr_t, VEC (occr_t, heap)): Define.
	(hoist_exprs): Remove.
	(alloc_code_hoist_mem, free_code_hoist_mem): Update.
	(compute_code_hoist_vbeinout): Add debug print outs.
	(hoist_code): Partially rewrite, simplify.  Use get_dominated_to_depth.

	* params.def (PARAM_MAX_HOIST_DEPTH): New parameter to avoid
	quadratic behavior.
	* params.h (MAX_HOIST_DEPTH): New macro.
	* doc/invoke.texi (max-hoist-depth): Document.

From-SVN: r162597

gcc/ChangeLog

 2010-07-27  Maxim Kuvyrkov  <maxim@codesourcery.com>
 
+	PR target/42495
+	PR middle-end/42574
+	* basic-block.h (get_dominated_to_depth): Declare.
+	* dominance.c (get_dominated_to_depth): New function, use
+	get_all_dominated_blocks as a base.
+	(get_all_dominated_blocks): Use get_dominated_to_depth.
+
+	* gcse.c (occr_t, VEC (occr_t, heap)): Define.
+	(hoist_exprs): Remove.
+	(alloc_code_hoist_mem, free_code_hoist_mem): Update.
+	(compute_code_hoist_vbeinout): Add debug print outs.
+	(hoist_code): Partially rewrite, simplify.  Use get_dominated_to_depth.
+
+	* params.def (PARAM_MAX_HOIST_DEPTH): New parameter to avoid
+	quadratic behavior.
+	* params.h (MAX_HOIST_DEPTH): New macro.
+	* doc/invoke.texi (max-hoist-depth): Document.
+
+2010-07-27  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
 	PR rtl-optimization/40956
 	* config/arm/arm.c (thumb1_size_rtx_costs): Fix cost of simple
 	constants.

gcc/basic-block.h

@@ -854,6 +854,8 @@ extern VEC (basic_block, heap) *get_dominated_by (enum cdi_direction, basic_bloc
 extern VEC (basic_block, heap) *get_dominated_by_region (enum cdi_direction,
 							 basic_block *,
 							 unsigned);
+extern VEC (basic_block, heap) *get_dominated_to_depth (enum cdi_direction,
+							basic_block, int);
 extern VEC (basic_block, heap) *get_all_dominated_blocks (enum cdi_direction,
 							  basic_block);
 extern void add_to_dominance_info (enum cdi_direction, basic_block);

gcc/doc/invoke.texi

@@ -8260,6 +8260,12 @@ the more aggressive code hoisting will be.  Specifying 0 will
 allow all expressions to travel unrestricted distances.
 The default value is 3.
 
+@item max-hoist-depth
+The depth of search in the dominator tree for expressions to hoist.
+This is used to avoid quadratic behavior in hoisting algorithm.
+The value of 0 will avoid limiting the search, but may slow down compilation
+of huge functions.  The default value is 30.
+
 @item max-unrolled-insns
 The maximum number of instructions that a loop should have if that loop
 is unrolled, and if the loop is unrolled, it determines how many times

gcc/dominance.c

@@ -784,16 +784,20 @@ get_dominated_by_region (enum cdi_direction dir, basic_block *region,
 }
 
 /* Returns the list of basic blocks including BB dominated by BB, in the
-   direction DIR.  The vector will be sorted in preorder.  */
+   direction DIR up to DEPTH in the dominator tree.  The DEPTH of zero will
+   produce a vector containing all dominated blocks.  The vector will be sorted
+   in preorder.  */
 
 VEC (basic_block, heap) *
-get_all_dominated_blocks (enum cdi_direction dir, basic_block bb)
+get_dominated_to_depth (enum cdi_direction dir, basic_block bb, int depth)
 {
   VEC(basic_block, heap) *bbs = NULL;
   unsigned i;
+  unsigned next_level_start;
 
   i = 0;
   VEC_safe_push (basic_block, heap, bbs, bb);
+  next_level_start = 1; /* = VEC_length (basic_block, bbs); */
 
   do
     {
@@ -804,12 +808,24 @@ get_all_dominated_blocks (enum cdi_direction dir, basic_block bb)
 	   son;
 	   son = next_dom_son (dir, son))
 	VEC_safe_push (basic_block, heap, bbs, son);
+
+      if (i == next_level_start && --depth)
+	next_level_start = VEC_length (basic_block, bbs);
     }
-  while (i < VEC_length (basic_block, bbs));
+  while (i < next_level_start);
 
   return bbs;
 }
 
+/* Returns the list of basic blocks including BB dominated by BB, in the
+   direction DIR.  The vector will be sorted in preorder.  */
+
+VEC (basic_block, heap) *
+get_all_dominated_blocks (enum cdi_direction dir, basic_block bb)
+{
+  return get_dominated_to_depth (dir, bb, 0);
+}
+
 /* Redirect all edges pointing to BB to TO.  */
 void
 redirect_immediate_dominators (enum cdi_direction dir, basic_block bb,

gcc/params.def

@@ -240,6 +240,14 @@ DEFPARAM(PARAM_GCSE_UNRESTRICTED_COST,
 	 "Cost at which GCSE optimizations will not constraint the distance an expression can travel",
 	 3, 0, 0)
 
+/* How deep from a given basic block the dominator tree should be searched
+   for expressions to hoist to the block.  The value of 0 will avoid limiting
+   the search.  */
+DEFPARAM(PARAM_MAX_HOIST_DEPTH,
+	 "max-hoist-depth",
+	 "Maximum depth of search in the dominator tree for expressions to hoist",
+	 30, 0, 0)
+
 /* This parameter limits the number of insns in a loop that will be unrolled,
    and by how much the loop is unrolled.
 

gcc/params.h

@@ -129,6 +129,8 @@ typedef enum compiler_param
   PARAM_VALUE (PARAM_GCSE_COST_DISTANCE_RATIO)
 #define GCSE_UNRESTRICTED_COST \
   PARAM_VALUE (PARAM_GCSE_UNRESTRICTED_COST)
+#define MAX_HOIST_DEPTH \
+  PARAM_VALUE (PARAM_MAX_HOIST_DEPTH)
 #define MAX_UNROLLED_INSNS \
   PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS)
 #define MAX_SMS_LOOP_NUMBER \