re PR rtl-optimization/8423 (CSE1 not propagating __builtin_constant_p enough)

	PR optimization/8423
	* cse.c (fold_rtx): Only eliminate a CONSTANT_P_RTX to 1 when
	its argument is constant, or 0 if !flag_gcse.
	* simplify-rtx.c (simplify_rtx): Convert CONSTANT_P_RTX to 1
	if it's argument is constant.
	* gcse.c (want_to_gcse_p): Ignore CONSTANT_P_RTX nodes.
	(hash_scan_set): Don't record CONSTANT_P_RTX expressions.
	(do_local_cprop): Don't propagate CONSTANT_P_RTX constants.
	* builtins.c (purge_builtin_constant_p): New function to force
	instantiation of any remaining CONSTANT_P_RTX nodes.
	* rtl.h (purge_builtin_constant_p): Prototype here.
	* toplev.c (rest_of_compilation): Invoke purge_builtin_constant_p
	pass after GCSE and before loop.
	(flag_gcse): No longer static.
	* flags.h (flag_gcse): Prototype here.

From-SVN: r61642

gcc/ChangeLog

+2003-01-22  Roger Sayle  <roger@eyesopen.com>
+
+	PR optimization/8423
+	* cse.c (fold_rtx): Only eliminate a CONSTANT_P_RTX to 1 when
+	its argument is constant, or 0 if !flag_gcse.
+	* simplify-rtx.c (simplify_rtx): Convert CONSTANT_P_RTX to 1
+	if it's argument is constant.
+	* gcse.c (want_to_gcse_p): Ignore CONSTANT_P_RTX nodes.
+	(hash_scan_set): Don't record CONSTANT_P_RTX expressions.
+	(do_local_cprop): Don't propagate CONSTANT_P_RTX constants.
+	* builtins.c (purge_builtin_constant_p): New function to force
+	instantiation of any remaining CONSTANT_P_RTX nodes.
+	* rtl.h (purge_builtin_constant_p): Prototype here.
+	* toplev.c (rest_of_compilation): Invoke purge_builtin_constant_p
+	pass after GCSE and before loop.
+	(flag_gcse): No longer static.
+	* flags.h (flag_gcse): Prototype here.
+
 2003-01-22  Ulrich Weigand  <uweigand@de.ibm.com>
 
 	* config/s390/s390.h (HARD_REGNO_MODE_OK): Fix warning regression

gcc/builtins.c

@@ -1461,8 +1461,8 @@ expand_builtin_constant_p (exp)
   arglist = TREE_VALUE (arglist);
 
   /* We have taken care of the easy cases during constant folding.  This
-     case is not obvious, so emit (constant_p_rtx (ARGLIST)) and let CSE get a
-     chance to see if it can deduce whether ARGLIST is constant.  */
+     case is not obvious, so emit (constant_p_rtx (ARGLIST)) and let CSE
+     get a chance to see if it can deduce whether ARGLIST is constant.  */
 
   tmp = expand_expr (arglist, NULL_RTX, VOIDmode, 0);
   tmp = gen_rtx_CONSTANT_P_RTX (value_mode, tmp);
@@ -4496,3 +4496,32 @@ default_expand_builtin (exp, target, subtarget, mode, ignore)
 {
   return NULL_RTX;
 }
+
+/* Instantiate all remaining CONSTANT_P_RTX nodes.  */
+
+void
+purge_builtin_constant_p ()
+{
+  rtx insn, done, set;
+  rtx arg, new, note;
+  basic_block bb;
+
+  FOR_EACH_BB (bb)
+    {
+      done = NEXT_INSN (bb->end);
+      for (insn = bb->head; insn != done; insn = NEXT_INSN (insn))
+	if (INSN_P (insn)
+	    && (set = single_set (insn)) != NULL_RTX
+	    && GET_CODE (SET_SRC (set)) == CONSTANT_P_RTX)
+	  {
+	    arg = XEXP (SET_SRC (set), 0);
+	    new = CONSTANT_P (arg) ? const1_rtx : const0_rtx;
+	    validate_change (insn, &SET_SRC (set), new, 0);
+
+	    /* Remove the REG_EQUAL note from the insn.  */
+	    if ((note = find_reg_note (insn, REG_EQUAL, NULL_RTX)) != 0)
+	      remove_note (insn, note);
+	  }
+    }
+}
+

gcc/cse.c

 /* Common subexpression elimination for GNU compiler.
    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998
-   1999, 2000, 2001, 2002 Free Software Foundation, Inc.
+   1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -4332,9 +4332,14 @@ fold_rtx (x, insn)
       break;
 
     case 'x':
-      /* Always eliminate CONSTANT_P_RTX at this stage.  */
+      /* Eliminate CONSTANT_P_RTX if its constant.  */
       if (code == CONSTANT_P_RTX)
-	return (const_arg0 ? const1_rtx : const0_rtx);
+	{
+	  if (const_arg0)
+	    return const1_rtx;
+	  if (!flag_gcse)
+	    return const0_rtx;
+	}
       break;
     }
 

gcc/flags.h

@@ -633,6 +633,10 @@ extern enum graph_dump_types graph_dump_format;
 
 extern int flag_no_ident;
 
+/* Nonzero means perform global CSE.  */
+
+extern int flag_gcse;
+
 /* Nonzero if we want to perform enhanced load motion during gcse.  */
 
 extern int flag_gcse_lm;

gcc/gcse.c

@@ -1305,6 +1305,7 @@ want_to_gcse_p (x)
     case CONST_DOUBLE:
     case CONST_VECTOR:
     case CALL:
+    case CONSTANT_P_RTX:
       return 0;
 
     default:
@@ -2216,7 +2217,8 @@ hash_scan_set (pat, insn, table)
 		    && REGNO (src) >= FIRST_PSEUDO_REGISTER
 		    && can_copy_p [GET_MODE (dest)]
 		    && REGNO (src) != regno)
-		   || CONSTANT_P (src))
+		   || (CONSTANT_P (src)
+		       && GET_CODE (src) != CONSTANT_P_RTX))
 	       /* A copy is not available if its src or dest is subsequently
 		  modified.  Here we want to search from INSN+1 on, but
 		  oprs_available_p searches from INSN on.  */
@@ -4277,7 +4279,8 @@ do_local_cprop (x, insn, alter_jumps, libcall_sp)
 	  if (l->in_libcall)
 	    continue;
 
-	  if (CONSTANT_P (this_rtx))
+	  if (CONSTANT_P (this_rtx)
+	      && GET_CODE (this_rtx) != CONSTANT_P_RTX)
 	    newcnst = this_rtx;
 	  if (REG_P (this_rtx) && REGNO (this_rtx) >= FIRST_PSEUDO_REGISTER
 	      /* Don't copy propagate if it has attached REG_EQUIV note.

gcc/rtl.h

@@ -1346,6 +1346,7 @@ extern int ceil_log2			PARAMS ((unsigned HOST_WIDE_INT));
 
 /* In builtins.c */
 extern rtx expand_builtin_expect_jump	PARAMS ((tree, rtx, rtx));
+extern void purge_builtin_constant_p	PARAMS ((void));
 
 /* In explow.c */
 extern void set_stack_check_libfunc PARAMS ((rtx));

gcc/simplify-rtx.c

 /* RTL simplification functions for GNU compiler.
    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002 Free Software Foundation, Inc.
+   1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -2729,11 +2729,15 @@ simplify_rtx (x)
 					     : GET_MODE (XEXP (x, 1))),
 					    XEXP (x, 0), XEXP (x, 1));
     case 'x':
-      /* The only case we try to handle is a SUBREG.  */
       if (code == SUBREG)
 	return simplify_gen_subreg (mode, SUBREG_REG (x),
 				    GET_MODE (SUBREG_REG (x)),
 				    SUBREG_BYTE (x));
+      if (code == CONSTANT_P_RTX)
+	{
+	  if (CONSTANT_P (XEXP (x,0)))
+	    return const1_rtx;
+	}
       return NULL;
     default:
       return NULL;

gcc/toplev.c

@@ -621,10 +621,6 @@ int flag_volatile_static;
 
 int flag_syntax_only = 0;
 
-/* Nonzero means perform global cse.  */
-
-static int flag_gcse;
-
 /* Nonzero means perform loop optimizer.  */
 
 static int flag_loop_optimize;
@@ -646,6 +642,10 @@ static int flag_if_conversion2;
 
 static int flag_delete_null_pointer_checks;
 
+/* Nonzero means perform global CSE.  */
+
+int flag_gcse = 0;
+
 /* Nonzero means to do the enhanced load motion during gcse, which trys
    to hoist loads by not killing them when a store to the same location
    is seen.  */
@@ -2921,6 +2921,9 @@ rest_of_compilation (decl)
 #endif
     }
 
+  /* Instantiate any remaining CONSTANT_P_RTX nodes.  */
+  purge_builtin_constant_p ();
+
   /* Move constant computations out of loops.  */
 
   if (optimize > 0 && flag_loop_optimize)