Undo bogus changes from gcc2 merge

From-SVN: r29407

gcc/ChangeLog

+Tue Sep 14 15:28:00 1999  Bernd Schmidt  <bernds@cygnus.co.uk>
+
+	Undo some changes from the gcc2 merge:
+	* rtl.def (CONSTANT_P_RTX): Fix the comment for this rtx code.
+	* emit-rtl.c (gen_rtx_REG): Don't test special reg rtx's for null
+	pointers.
+
+	Undo this change:
+	Sat Oct  3 07:20:28 1998  Stephen L Moshier  <moshier@world.std.com>
+	* emit-rtl.c (gen_lowpart_common): Disable optimization of
+	initialized float-int union if the value is a NaN.
+
 Tue Sep 14 04:03:44 1999  Mumit Khan  <khan@xraylith.wisc.edu>
 
 	* gthr-win32.h: New file.

gcc/emit-rtl.c

@@ -251,22 +251,21 @@ gen_rtx_REG (mode, regno)
 
   if (mode == Pmode && !reload_in_progress)
     {
-      if (frame_pointer_rtx != 0 && regno == FRAME_POINTER_REGNUM)
+      if (regno == FRAME_POINTER_REGNUM)
 	return frame_pointer_rtx;
 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
-      if (hard_frame_pointer_rtx != 0 && regno == HARD_FRAME_POINTER_REGNUM)
+      if (regno == HARD_FRAME_POINTER_REGNUM)
 	return hard_frame_pointer_rtx;
 #endif
 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM && HARD_FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
-      if (arg_pointer_rtx != 0 && regno == ARG_POINTER_REGNUM)
+      if (regno == ARG_POINTER_REGNUM)
 	return arg_pointer_rtx;
 #endif
 #ifdef RETURN_ADDRESS_POINTER_REGNUM
-      if (return_address_pointer_rtx != 0
-	  && regno == RETURN_ADDRESS_POINTER_REGNUM)
+      if (regno == RETURN_ADDRESS_POINTER_REGNUM)
 	return return_address_pointer_rtx;
 #endif
-      if (stack_pointer_rtx != 0 && regno == STACK_POINTER_REGNUM)
+      if (regno == STACK_POINTER_REGNUM)
 	return stack_pointer_rtx;
     }
 
@@ -752,9 +751,6 @@ gen_lowpart_common (mode, x)
 
       i = INTVAL (x);
       r = REAL_VALUE_FROM_TARGET_SINGLE (i);
-      /* Avoid changing the bit pattern of a NaN.  */
-      if (REAL_VALUE_ISNAN (r))
-	return 0;
       return CONST_DOUBLE_FROM_REAL_VALUE (r, mode);
     }
 #else
@@ -793,8 +789,6 @@ gen_lowpart_common (mode, x)
 	i[0] = low, i[1] = high;
 
       r = REAL_VALUE_FROM_TARGET_DOUBLE (i);
-      if (REAL_VALUE_ISNAN (r))
-	return 0;
       return CONST_DOUBLE_FROM_REAL_VALUE (r, mode);
     }
 #else

gcc/rtl.def

@@ -530,13 +530,8 @@ DEF_RTL_EXPR(CONST_STRING, "const_string", "s", 'o')
 /* This is used to encapsulate an expression whose value is constant
    (such as the sum of a SYMBOL_REF and a CONST_INT) so that it will be
    recognized as a constant operand rather than by arithmetic instructions.  */
-DEF_RTL_EXPR(CONST, "const", "e", 'o')
 
-/* A unary `__builtin_constant_p' expression.  This RTL code may only be used
-   as an operand of a CONST.  This pattern is only emitted during RTL
-   generation and then only if optimize > 0.  It is converted by the first
-   CSE pass into the appropriate CONST_INT.  */
-DEF_RTL_EXPR(CONSTANT_P_RTX, "constant_p_rtx", "e", 'x')
+DEF_RTL_EXPR(CONST, "const", "e", 'o')
 
 /* program counter.  Ordinary jumps are represented
    by a SET whose first operand is (PC).  */
@@ -855,6 +850,11 @@ DEF_RTL_EXPR(RANGE_VAR, "range_var", "eti", 'x')
    0 is the live bitmap.  Operand 1 is the original block number.  */
 DEF_RTL_EXPR(RANGE_LIVE, "range_live", "bi", 'x')
 
+/* A unary `__builtin_constant_p' expression.  These are only emitted
+   during RTL generation, and then only if optimize > 0.  They are
+   eliminated by the first CSE pass. */
+DEF_RTL_EXPR(CONSTANT_P_RTX, "constant_p_rtx", "e", 'x')
+
 /* A placeholder for a CALL_INSN which may be turned into a normal call,
    a sibling (tail) call or tail recursion.