re PR debug/49888 (VTA: -O2 -g variable value changes, it does not change in the...

re PR debug/49888 (VTA: -O2 -g variable value changes, it does not change in the source)

gcc/ChangeLog:
PR debug/49888
* var-tracking.c: Include alias.h.
(overlapping_mems): New struct.
(drop_overlapping_mem_locs): New.
(clobber_overlapping_mems): New.
(var_mem_delete_and_set, var_mem_delete): Call it.
(val_bind): Likewise, but only if modified.
(compute_bb_dataflow, emit_notes_in_bb): Call it on MEMs.
* Makefile.in (var-tracking.o): Depend in $(ALIAS_H).
gcc/testsuite/ChangeLog:
PR debug/49888
* gcc.dg/guality/pr49888.c: New.

From-SVN: r188531