[Ada] Generate fewer conditional branches around For loops

[Eric Botcazou]

The goal of this patch is to generate fewer conditional branches around loops 
with a For iteration scheme and dynamic bounds.  The strategy is two-fold: 
at -O0, try to generate the loop forms with the fewer conditional branches 
directly; at -O1 or above, try to generate the do-while form expected by the 
loop optimizer directly, so that loop header copying is bypassed.

Tested on x86_64-suse-linux, applied on the mainline.


2010-04-16  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/ada-tree.def (LOOP_STMT): Change to 4-operand nodes.
	* gcc-interface/ada-tree.h (LOOP_STMT_TOP_COND, LOOP_STMT_BOT_COND):
	Merge into...
	(LOOP_STMT_COND): ...this.
	(LOOP_STMT_BOTTOM_COND_P): New flag.
	(LOOP_STMT_TOP_UPDATE_P): Likewise.
	* gcc-interface/trans.c (can_equal_min_or_max_val_p): New function.
	(can_equal_min_val_p): New static inline function.
	(can_equal_max_val_p): Likewise.
	(Loop_Statement_to_gnu): Use build4 in lieu of build5 and adjust to
	new LOOP_STMT semantics.  Use two different strategies depending on
	whether optimization is enabled to translate the loop.
	(gnat_gimplify_stmt) <LOOP_STMT>: Adjust to new LOOP_STMT semantics.


-- 
Eric Botcazou
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