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

1 files changed, 17 insertions, 0 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 73051de..0db0f59 100644
--- a/gcc/doc/invoke.texi
+++ b/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