regrename.c (copyprop_hardreg_forward): New optimization.

        * regrename.c (copyprop_hardreg_forward): New optimization.
        (kill_value_regno, kill_value, init_value_data, kill_clobbered_value,
        kill_set_value, kill_autoinc_value, copy_value, find_oldest_value_reg,
        replace_oldest_value_reg, replace_oldest_value_addr,
        replace_oldest_value_mem, copyprop_hardreg_forward_1,
        debug_value_data, validate_value_data): New.
        * rtl.h (copyprop_hardreg_forward): Declare.
        * toplev.c (flag_cprop_registers): New.
        (f_options): Add -fcprop-registers
        (rest_of_compilation): Invoke it.
        (parse_options_and_default_flags): Set it at -O1.
        * doc/invoke.texi: Document it.

From-SVN: r47951

gcc/ChangeLog

+2001-12-12  Richard Henderson  <rth@redhat.com>
+
+	* regrename.c (copyprop_hardreg_forward): New optimization.
+	(kill_value_regno, kill_value, init_value_data, kill_clobbered_value,
+	kill_set_value, kill_autoinc_value, copy_value, find_oldest_value_reg,
+	replace_oldest_value_reg, replace_oldest_value_addr,
+	replace_oldest_value_mem, copyprop_hardreg_forward_1,
+	debug_value_data, validate_value_data): New.
+	* rtl.h (copyprop_hardreg_forward): Declare.
+	* toplev.c (flag_cprop_registers): New.
+	(f_options): Add -fcprop-registers
+	(rest_of_compilation): Invoke it.
+	(parse_options_and_default_flags): Set it at -O1.
+	* doc/invoke.texi: Document it.
+
 2001-12-12  Jakub Jelinek  <jakub@redhat.com>
 
 	* dwarf2out.c (dw_val_class): Add dw_val_class_range_list.

gcc/doc/invoke.texi

@@ -259,7 +259,7 @@ in the following sections.
 @gccoptlist{
 -falign-functions=@var{n}  -falign-jumps=@var{n} @gol
 -falign-labels=@var{n}  -falign-loops=@var{n}  @gol
--fbranch-probabilities  -fcaller-saves @gol
+-fbranch-probabilities  -fcaller-saves -fcprop-registers @gol
 -fcse-follow-jumps  -fcse-skip-blocks  -fdata-sections @gol
 -fdelayed-branch  -fdelete-null-pointer-checks @gol
 -fexpensive-optimizations  -ffast-math  -ffloat-store @gol
@@ -3774,6 +3774,12 @@ will most benefit processors with lots of registers.  It can, however,
 make debugging impossible, since variables will no longer stay in
 a ``home register''.
 
+@item -fno-cprop-registers
+@opindex fno-cprop-registers
+After register allocation and post-register allocation instruction splitting,
+we perform a copy-propagation pass to try to reduce scheduling dependencies
+and occasionally eliminate the copy.
+
 @item --param @var{name}=@var{value}
 @opindex param
 In some places, GCC uses various constants to control the amount of

gcc/rtl.h

@@ -2097,6 +2097,7 @@ extern rtx stack_limit_rtx;
 
 /* In regrename.c */
 extern void regrename_optimize		PARAMS ((void));
+extern void copyprop_hardreg_forward	PARAMS ((void));
 
 /* In ifcvt.c */
 extern void if_convert			PARAMS ((int));

gcc/toplev.c

@@ -427,6 +427,7 @@ int flag_reorder_blocks = 0;
 /* Nonzero if registers should be renamed.  */
 
 int flag_rename_registers = 0;
+int flag_cprop_registers = 0;
 
 /* Nonzero for -pedantic switch: warn about anything
    that standard spec forbids.  */
@@ -1083,6 +1084,8 @@ lang_independent_options f_options[] =
    N_("Reorder basic blocks to improve code placement") },
   {"rename-registers", &flag_rename_registers, 1,
    N_("Do the register renaming optimization pass") },
+  {"cprop-registers", &flag_cprop_registers, 1,
+   N_("Do the register copy-propagation optimization pass") },
   {"common", &flag_no_common, 0,
    N_("Do not put uninitialized globals in the common section") },
   {"inhibit-size-directive", &flag_inhibit_size_directive, 1,
@@ -3280,12 +3283,15 @@ rest_of_compilation (decl)
     }
 #endif
 
-  if (optimize > 0 && flag_rename_registers)
+  if (flag_rename_registers || flag_cprop_registers)
     {
       timevar_push (TV_RENAME_REGISTERS);
       open_dump_file (DFI_rnreg, decl);
 
-      regrename_optimize ();
+      if (flag_rename_registers)
+        regrename_optimize ();
+      if (flag_cprop_registers)
+        copyprop_hardreg_forward ();
 
       close_dump_file (DFI_rnreg, print_rtl_with_bb, insns);
       timevar_pop (TV_RENAME_REGISTERS);
@@ -4620,6 +4626,7 @@ parse_options_and_default_flags (argc, argv)
       flag_omit_frame_pointer = 1;
 #endif
       flag_guess_branch_prob = 1;
+      flag_cprop_registers = 1;
     }
 
   if (optimize >= 2)