gcse.c (struct expr:max_distance): New field.

	* gcse.c (struct expr:max_distance): New field.
	(doing_code_hoisting_p): New static variable.
	(want_to_gcse_p): Change signature.  Allow constrained hoisting of
	simple expressions, don't change behavior for PRE.  Set max_distance.
	(insert_expr_in_table): Set new max_distance field.
	(hash_scan_set): Update.
	(hoist_expr_reaches_here_p): Stop search after max_distance
	instructions.
	(find_occr_in_bb): New static function.  Use it in ...
	(hoist_code): Calculate sizes of basic block before any changes are
	done.  Pass max_distance to hoist_expr_reaches_here_p.
	(one_code_hoisting_pass): Set doing_code_hoisting_p.

	* params.def (PARAM_GCSE_COST_DISTANCE_RATIO,)
	(PARAM_GCSE_UNRESTRICTED_COST): New parameters.
	* params.h (GCSE_COST_DISTANCE_RATIO, GCSE_UNRESTRICTED_COST): New
	macros.
	* doc/invoke.texi (gcse-cost-distance-ratio, gcse-unrestricted-cost):
	Document.

From-SVN: r162589

gcc/ChangeLog

+2010-07-27  Maxim Kuvyrkov  <maxim@codesourcery.com>
+
+	* gcse.c (struct expr:max_distance): New field.
+	(doing_code_hoisting_p): New static variable.
+	(want_to_gcse_p): Change signature.  Allow constrained hoisting of
+	simple expressions, don't change behavior for PRE.  Set max_distance.
+	(insert_expr_in_table): Set new max_distance field.
+	(hash_scan_set): Update.
+	(hoist_expr_reaches_here_p): Stop search after max_distance
+	instructions.
+	(find_occr_in_bb): New static function.  Use it in ...
+	(hoist_code): Calculate sizes of basic block before any changes are
+	done.  Pass max_distance to hoist_expr_reaches_here_p.
+	(one_code_hoisting_pass): Set doing_code_hoisting_p.
+
+	* params.def (PARAM_GCSE_COST_DISTANCE_RATIO,)
+	(PARAM_GCSE_UNRESTRICTED_COST): New parameters.
+	* params.h (GCSE_COST_DISTANCE_RATIO, GCSE_UNRESTRICTED_COST): New
+	macros.
+	* doc/invoke.texi (gcse-cost-distance-ratio, gcse-unrestricted-cost):
+	Document.
+
 2010-07-27  Jeff Law  <law@redhat.com>
 	    Maxim Kuvyrkov  <maxim@codesourcery.com>
 

gcc/doc/invoke.texi

@@ -8243,6 +8243,23 @@ when @option{-ftree-vectorize} is used.  The number of iterations after
 vectorization needs to be greater than the value specified by this option
 to allow vectorization.  The default value is 0.
 
+@item gcse-cost-distance-ratio
+Scaling factor in calculation of maximum distance an expression
+can be moved by GCSE optimizations.  This is currently supported only in
+code hoisting pass.  The bigger the ratio, the more agressive code hoisting
+will be with simple expressions, i.e., the expressions which have cost
+less than @option{gcse-unrestricted-cost}.  Specifying 0 will disable
+hoisting of simple expressions.  The default value is 10.
+
+@item gcse-unrestricted-cost
+Cost, roughly measured as the cost of a single typical machine
+instruction, at which GCSE optimizations will not constrain
+the distance an expression can travel.  This is currently
+supported only in code hoisting pass.  The lesser the cost,
+the more aggressive code hoisting will be.  Specifying 0 will
+allow all expressions to travel unrestricted distances.
+The default value is 3.
+
 @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/params.def

@@ -225,6 +225,21 @@ DEFPARAM(PARAM_GCSE_AFTER_RELOAD_CRITICAL_FRACTION,
 	"gcse-after-reload-critical-fraction",
 	"The threshold ratio of critical edges execution count that permit performing redundancy elimination after reload",
         10, 0, 0)
+
+/* GCSE will use GCSE_COST_DISTANCE_RATION as a scaling factor
+   to calculate maximum distance for which an expression is allowed to move
+   from its rtx_cost.  */
+DEFPARAM(PARAM_GCSE_COST_DISTANCE_RATIO,
+	 "gcse-cost-distance-ratio",
+	 "Scaling factor in calculation of maximum distance an expression can be moved by GCSE optimizations",
+	 10, 0, 0)
+/* GCSE won't restrict distance for which an expression with rtx_cost greater
+   than COSTS_N_INSN(GCSE_UNRESTRICTED_COST) is allowed to move.  */
+DEFPARAM(PARAM_GCSE_UNRESTRICTED_COST,
+	 "gcse-unrestricted-cost",
+	 "Cost at which GCSE optimizations will not constraint the distance an expression can travel",
+	 3, 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

@@ -125,6 +125,10 @@ typedef enum compiler_param
   PARAM_VALUE (PARAM_GCSE_AFTER_RELOAD_PARTIAL_FRACTION)
 #define GCSE_AFTER_RELOAD_CRITICAL_FRACTION \
   PARAM_VALUE (PARAM_GCSE_AFTER_RELOAD_CRITICAL_FRACTION)
+#define GCSE_COST_DISTANCE_RATIO \
+  PARAM_VALUE (PARAM_GCSE_COST_DISTANCE_RATIO)
+#define GCSE_UNRESTRICTED_COST \
+  PARAM_VALUE (PARAM_GCSE_UNRESTRICTED_COST)
 #define MAX_UNROLLED_INSNS \
   PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS)
 #define MAX_SMS_LOOP_NUMBER \