Makefile.in (OBJS): Added dce.o.

	* Makefile.in (OBJS): Added dce.o.
	(ssa.o): Updated target to include ssa.h.
	(flow.o): Likewise.
	(toplev.o): Likewise.
	(dce.o): Created target.
	* basic-block.h: Added comments.
	(INVALID_BLOCK): Added definition.
	(connect_infinite_loops_to_exit): Added declaration.
	Moved SSA declarations to ssa.h.
	* flow.c: Added inclusion of ssa.h.
	(struct depth_first_search_dsS, depth_first_search_ds):
	Added definitions.
	(compute_immediate_postdominators): Added definition.
	(connect_infinite_loops_to_exit): Likewise.
	(flow_dfs_compute_reverse_init): Likewise.
	(flow_dfs_compute_reverse_add_bb): Likewise.
	(flow_dfs_compute_reverse_execute): Likewise.
	(flow_dfs_compute_reverse_finish): Likewise.
	* rtl.h (rtx/in_struct): Added use to determine insn necessity.
	(LABEL_P): Added definition.
	(JUMP_P): Likewise.
	(NOTE_P): Likewise.
	(BARRIER_P): Likewise.
	(JUMP_TABLE_DATA_P): Likewise.
	(INSN_DEAD_CODE_P): Likewise.
	* ssa.c: Replaced inclusions with ssa.h inclusion.
	(CONVERT_HARD_REGISTER_TO_SSA_P): Moved to ssa.h.
	(rename_registers): Removed unnecessary variables.
	* ssa.h: Created by moving declarations from ssa.c and
	basic-block.h.
	* timevar.def: Defined TV_DEAD_CODE_ELIM.
	* toplev.c: Added ssa.h inclusion.
	(dump_file_index): Added DFI_dce.
	(dump_file): Added "dce" entry.
	Defined flag_ssa.
	(f_options): Added dce entry.
	* invoke.texi: Document -fdce.  Emphasize experimental status of
	-fssa.

Co-Authored-By: Mark Mitchell <mark@codesourcery.com>

From-SVN: r35419

1 files changed, 23 insertions, 3 deletions

diff --git a/gcc/toplev.c b/gcc/toplev.c
index fde14d1..b13e580 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -63,6 +63,7 @@ Boston, MA 02111-1307, USA.  */
 #include "regs.h"
 #include "timevar.h"
 #include "diagnostic.h"
+#include "ssa.h"
 
 #ifndef ACCUMULATE_OUTGOING_ARGS
 #define ACCUMULATE_OUTGOING_ARGS 0
@@ -259,6 +260,7 @@ enum dump_file_index
   DFI_cse,
   DFI_addressof,
   DFI_ssa,
+  DFI_dce,
   DFI_ussa,
   DFI_gcse,
   DFI_loop,
@@ -291,7 +293,7 @@ enum dump_file_index
    Remaining -d letters:
 
 	"       h      o q   u     "
-	"       H  K   OPQ  TUVWXYZ"
+	"       H  K   OPQ  TUVW YZ"
 */
 
 struct dump_file_info dump_file[DFI_MAX] = 
@@ -302,6 +304,7 @@ struct dump_file_info dump_file[DFI_MAX] =
   { "cse",	's', 0, 0, 0 },
   { "addressof", 'F', 0, 0, 0 },
   { "ssa",	'e', 1, 0, 0 },
+  { "dce",	'X', 1, 0, 0 },
   { "ussa",	'e', 1, 0, 0 },	/* Yes, duplicate enable switch.  */
   { "gcse",	'G', 1, 0, 0 },
   { "loop",	'L', 1, 0, 0 },
@@ -786,6 +789,9 @@ int flag_gnu_linker = 1;
 /* Enable SSA.  */
 int flag_ssa = 0;
 
+/* Enable dead code elimination. */
+int flag_dce = 0;
+
 /* Tag all structures with __attribute__(packed) */
 int flag_pack_struct = 0;
 
@@ -1094,6 +1100,8 @@ lang_independent_options f_options[] =
    "Instrument function entry/exit with profiling calls"},
   {"ssa", &flag_ssa, 1,
    "Enable SSA optimizations" },
+  {"dce", &flag_dce, 1,
+   "Enable dead code elimination" },
   {"leading-underscore", &flag_leading_underscore, 1,
    "External symbols have a leading underscore" },
   {"ident", &flag_no_ident, 0,
@@ -2976,13 +2984,25 @@ rest_of_compilation (decl)
       close_dump_file (DFI_ssa, print_rtl_with_bb, insns);
       timevar_pop (TV_TO_SSA);
 
-      /* Currently, there's nothing to do in SSA form.  */
-
       /* The SSA implementation uses basic block numbers in its phi
 	 nodes.  Thus, changing the control-flow graph or the basic
 	 blocks, e.g., calling find_basic_blocks () or cleanup_cfg (),
 	 may cause problems.  */
 
+      if (flag_dce)
+	{
+	  /* Remove dead code. */
+
+	  timevar_push (TV_DEAD_CODE_ELIM);
+	  open_dump_file (DFI_dce, decl);
+
+	  insns = get_insns ();
+	  eliminate_dead_code();
+  
+	  close_dump_file (DFI_dce, print_rtl_with_bb, insns);
+	  timevar_pop (TV_DEAD_CODE_ELIM);
+	}
+
       /* Convert from SSA form.  */
 
       timevar_push (TV_FROM_SSA);