[RFC] [Patch] PR67326 - relax trap assumption by looking at similar DRS

["Kumar, Venkataramanan" <Venkataramanan dot Kumar at amd dot com>]

Hi Richard,

As per Jakub suggestion in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67326, the below patch fixes the regression in tree if conversion.
Basically allowing if conversion to happen for a candidate DR, if we find similar DR with same dimensions  and that DR will not trap.

To find similar DRs using hash table to hashing the offset and DR pairs.  
Also reusing  read/written information that was stored for reference tree.  

Also. 
(1) I guard these checks for  -ftree-loop-if-convert-stores and -fno-common. 
Sometimes vectorization flags also triggers if conversion.
(2) Also hashing base DRs for writes only. 

gcc/ChangeLog
2015-11-19  Venkataramanan  <Venkataramanan.Kumar@amd.com>
	
	PR tree-optimization/67326
	* tree-if-conv.c  (offset_DR_map): Define.
    	(struct ifc_dr): Add new tree base_predicate field.
    	(hash_memrefs_baserefs_and_store_DRs_read_written_info): Hash offsets, DR pairs
	and hash base ref,  DR pairs  for write type DRs.
	(ifcvt_memrefs_wont_trap):  Guard checks with -ftree-loop-if-convert-stores flag. 
       Check for similar DR that are accessed unconditionally.
       (if_convertible_loop_p_1):  Initialize and delete offset hash maps

gcc/testsuite/ChangeLog
2015-11-19  Venkataramanan  <Venkataramanan.Kumar@amd.com>
	* gcc.dg/tree-ssa/ifc-pr67326.c:  Add new.

Regstrapped on x86_64, Ok for trunk?

Regards,
Venkat.

Attachment: relax-trap-assumptions-fix-pr67326.txt
Description: relax-trap-assumptions-fix-pr67326.txt