Index: tree-pass.h
===================================================================
--- tree-pass.h	(revision 111268)
+++ tree-pass.h	(working copy)
@@ -353,6 +353,7 @@
 extern struct tree_opt_pass pass_regmove;
 extern struct tree_opt_pass pass_split_all_insns;
 extern struct tree_opt_pass pass_mode_switching;
+extern struct tree_opt_pass pass_see;
 extern struct tree_opt_pass pass_recompute_reg_usage;
 extern struct tree_opt_pass pass_sms;
 extern struct tree_opt_pass pass_sched;
Index: opts.c
===================================================================
--- opts.c	(revision 111268)
+++ opts.c	(working copy)
@@ -596,6 +596,7 @@
       flag_inline_functions = 1;
       flag_unswitch_loops = 1;
       flag_gcse_after_reload = 1;
+      flag_see = 1; 
     }
 
   if (optimize < 2 || optimize_size)
Index: timevar.def
===================================================================
--- timevar.def	(revision 111268)
+++ timevar.def	(working copy)
@@ -143,6 +143,7 @@
 DEFTIMEVAR (TV_FLOW                  , "flow analysis")
 DEFTIMEVAR (TV_COMBINE               , "combiner")
 DEFTIMEVAR (TV_IFCVT		     , "if-conversion")
+DEFTIMEVAR (TV_SEE                   , "see")
 DEFTIMEVAR (TV_REGMOVE               , "regmove")
 DEFTIMEVAR (TV_MODE_SWITCH           , "mode switching")
 DEFTIMEVAR (TV_SMS		     , "sms modulo scheduling")
Index: common.opt
===================================================================
--- common.opt	(revision 111268)
+++ common.opt	(working copy)
@@ -795,6 +795,10 @@
 Common Report Var(flag_rtl_seqabstr)
 Perform sequence abstraction optimization on RTL
 
+fsee
+Common Report Var(flag_see) Init(0)
+Eliminate redundant sign extensions using LCM.
+
 fshared-data
 Common Report Var(flag_shared_data)
 Mark data as shared rather than private
Index: Makefile.in
===================================================================
--- Makefile.in	(revision 111268)
+++ Makefile.in	(working copy)
@@ -987,7 +987,7 @@
  real.o recog.o reg-stack.o regclass.o regmove.o regrename.o		   \
  reload.o reload1.o reorg.o resource.o rtl.o rtlanal.o rtl-error.o	   \
  sbitmap.o sched-deps.o sched-ebb.o sched-rgn.o sched-vis.o sdbout.o	   \
- simplify-rtx.o sreal.o stmt.o stor-layout.o stringpool.o		   \
+ see.o simplify-rtx.o sreal.o stmt.o stor-layout.o stringpool.o		   \
  struct-equiv.o targhooks.o timevar.o toplev.o tracer.o tree.o tree-dump.o \
  varasm.o varray.o vec.o version.o vmsdbgout.o xcoffout.o alloc-pool.o	   \
  et-forest.o cfghooks.o bt-load.o pretty-print.o $(GGC) web.o passes.o	   \
@@ -2302,6 +2302,9 @@
 web.o : web.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    hard-reg-set.h $(FLAGS_H) $(BASIC_BLOCK_H) $(FUNCTION_H) output.h toplev.h \
    $(DF_H) $(OBSTACK_H) timevar.h tree-pass.h
+see.o : see.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
+   hard-reg-set.h $(FLAGS_H) $(BASIC_BLOCK_H) function.h output.h toplev.h \
+   $(DF_H) $(OBSTACK_H) timevar.h tree-pass.h
 gcse.o : gcse.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
    $(REGS_H) hard-reg-set.h $(FLAGS_H) real.h insn-config.h $(GGC_H) \
    $(RECOG_H) $(EXPR_H) $(BASIC_BLOCK_H) $(FUNCTION_H) output.h toplev.h \
Index: passes.c
===================================================================
--- passes.c	(revision 111268)
+++ passes.c	(working copy)
@@ -651,6 +651,7 @@
   NEXT_PASS (pass_regmove);
   NEXT_PASS (pass_split_all_insns);
   NEXT_PASS (pass_mode_switching);
+  NEXT_PASS (pass_see);
   NEXT_PASS (pass_recompute_reg_usage);
   NEXT_PASS (pass_sms);
   NEXT_PASS (pass_sched);
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 111268)
+++ doc/invoke.texi	(working copy)
@@ -332,7 +332,7 @@
 -fsched-spec-load-dangerous  @gol
 -fsched-stalled-insns=@var{n} -fsched-stalled-insns-dep=@var{n} @gol
 -fsched2-use-superblocks @gol
--fsched2-use-traces -freschedule-modulo-scheduled-loops @gol
+-fsched2-use-traces -fsee -freschedule-modulo-scheduled-loops @gol
 -fsection-anchors  -fsignaling-nans  -fsingle-precision-constant @gol
 -fstack-protector  -fstack-protector-all @gol
 -fstrength-reduce  -fstrict-aliasing  -ftracer  -fthread-jumps @gol
@@ -4989,6 +4989,12 @@
 sense when scheduling after register allocation, i.e.@: with
 @option{-fschedule-insns2} or at @option{-O2} or higher.
 
+@item -fsee
+@opindex fsee
+Eliminates redundant extension instructions and move the non redundant
+ones to optimal placement using LCM.
+Enabled at level @option{-O3}.
+
 @item -freschedule-modulo-scheduled-loops
 @opindex fscheduling-in-modulo-scheduled-loops
 The modulo scheduling comes before the traditional scheduling, if a loop was modulo scheduled