[PATCH] Fix Tree-SRA bug with array slices

[Eric Botcazou]

Hi,

The Tree-SRA pass mishandles array slices (aka ARRAY_RANGE_REFs).  For 
example, on the attached testcase compiled at -O, it turns

<bb 2>:
  key = "XXX";
  key[1 ...]{lb: 1 sz: 1} = "__";
  key = key;
  D.614_7 = key[3]{lb: 1 sz: 1};

into

<bb 2>:
  key$3_3 = "XXX"[3]{lb: 1 sz: 1};
  key$2_8 = "XXX"[2]{lb: 1 sz: 1};
  key$1_9 = "XXX"[1]{lb: 1 sz: 1};
  key[1 ...]{lb: 1 sz: 1} = "__";
  key$3_10 = key[3]{lb: 1 sz: 1};
  key$2_11 = key[2]{lb: 1 sz: 1};
  key$1_12 = key[1]{lb: 1 sz: 1};
  key$2_13 = key$2_11;
  key$1_14 = key$1_12;
  key$3_15 = key$3_10;
  D.614_7 = key$3_15;

Note how key$3_10, key$3_15 and eventually D.614_7 are loaded with garbage.
The proposed fix is to treat ARRAY_RANGE_REFs as groups of ARRAY_REFs.  The 
end result on the testcase is

<bb 2>:
  key$3_3 = "XXX"[3]{lb: 1 sz: 1};
  key$2_8 = "XXX"[2]{lb: 1 sz: 1};
  key$1_9 = "XXX"[1]{lb: 1 sz: 1};
  key$2_10 = "__"[2]{lb: 1 sz: 1};
  key$1_11 = "__"[1]{lb: 1 sz: 1};
  key$2_12 = key$2_10;
  key$1_13 = key$1_11;
  key$3_14 = key$3_3;
  D.614_7 = key$3_14;


Bootstrapped/regtested on i586-suse-linux.  OK for mainline?


2006-06-18  Eric Botcazou  <ebotcazou@adacore.com>

	* tree.c (range_in_array_bounds_p): New predicate.
	* tree.h (range_in_array_bounds_p): Declare it.
	* tree-eh.c (tree_could_trap_p) <ARRAY_RANGE_REF>: Use it to
	return a less conservative answer.
	* tree-sra.c (struct sra_elt): Add new pointer field 'groups'
	and flag 'is_group'.
	(IS_ELEMENT_FOR_GROUP): New macro.
	(FOR_EACH_ACTUAL_CHILD): Likewise.
	(next_child_for_group): New helper function.
	(can_completely_scalarize_p): Take into account groups.
	(sra_hash_tree): Handle RANGE_EXPR.
	(sra_elt_eq): Likewise.
	(lookup_element): Be prepared for handling groups.
	(is_valid_const_index): Delete.
	(maybe_lookup_element_for_expr) <ARRAY_REF>: Use in_array_bounds_p
	instead of is_valid_const_index.
	<ARRAY_RANGE_REF>: New case.
	(sra_walk_expr) <ARRAY_REF>: Use in_array_bounds_p instead of
	is_valid_const_index.
	<ARRAY_RANGE_REF>: Do not unconditionally punt.
	(scan_dump): Dump info for groups too.
	(decide_instantiation_1): Likewise.
	(decide_block_copy): Assert that the element is not a group.
	Propagate decision to groups.
	(generate_one_element_ref): Handle RANGE_EXPR.
	(mark_no_warning): Iterate over actual childs.
	(generate_copy_inout): Likewise.
	(generate_element_copy): Likewise.
	(generate_element_zero): Likewise.
	(generate_element_init_1): Likewise.
	(dump_sra_elt_name): Handle RANGE_EXPR.


-- 
Eric Botcazou
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