rtl.def (SS_ASHIFT, SS_NEG): New codes.

* rtl.def (SS_ASHIFT, SS_NEG): New codes.
	* doc/rtl.texi: Document them.
	* simplify-rtx.c (simplify_unary_operation,
	simplify_binary_operation_1): Don't abort when we see them.

From-SVN: r113227

gcc/ChangeLog

@@ -1,3 +1,10 @@
+2006-04-24  Bernd Schmidt  <bernd.schmidt@analog.com>
+
+	* rtl.def (SS_ASHIFT, SS_NEG): New codes.
+	* doc/rtl.texi: Document them.
+	* simplify-rtx.c (simplify_unary_operation,
+	simplify_binary_operation_1): Don't abort when we see them.
+
 2006-04-24  Mark Mitchell  <mark@codesourcery.com>
 
 	Revert:

gcc/doc/rtl.texi

@@ -1889,9 +1889,18 @@ or the first operand must be loaded into a register while its mode is
 still known.
 
 @findex neg
+@findex ss_neg
+@cindex negation
+@cindex negation with signed saturation
 @item (neg:@var{m} @var{x})
-Represents the negation (subtraction from zero) of the value represented
-by @var{x}, carried out in mode @var{m}.
+@itemx (ss_neg:@var{m} @var{x})
+These two expressions represent the negation (subtraction from zero) of
+the value represented by @var{x}, carried out in mode @var{m}.  They
+differ in the behaviour on overflow of integer modes.  In the case of
+@code{neg}, the negation of the operand may be a number not representable
+in mode @var{m}, in which case it is truncated to @var{m}.  @code{ss_neg}
+ensures that an out-of-bounds result saturates to the maximum or minimum
+representable value.
 
 @findex mult
 @cindex multiplication
@@ -1998,12 +2007,21 @@ and @var{y}, carried out in machine mode @var{m}, which must be a
 fixed-point mode.
 
 @findex ashift
+@findex ss_ashift
 @cindex left shift
 @cindex shift
 @cindex arithmetic shift
+@cindex arithmetic shift with signed saturation
 @item (ashift:@var{m} @var{x} @var{c})
-Represents the result of arithmetically shifting @var{x} left by @var{c}
-places.  @var{x} have mode @var{m}, a fixed-point machine mode.  @var{c}
+@itemx (ss_ashift:@var{m} @var{x} @var{c})
+These two expressions epresent the result of arithmetically shifting @var{x}
+left by @var{c} places.  They differ in their behavior on overflow of integer
+modes.  An @code{ashift} operation is a plain shift with no special behaviour
+in case of a change in the sign bit; @code{ss_ashift} saturates to the minimum
+or maximum representable value rather than allowing the shift to change the
+sign bit of the value.
+
+@var{x} have mode @var{m}, a fixed-point machine mode.  @var{c}
 be a fixed-point mode or be a constant with mode @code{VOIDmode}; which
 mode is determined by the mode called for in the machine description
 entry for the left-shift instruction.  For example, on the VAX, the mode

gcc/rtl.def

@@ -642,6 +642,12 @@ DEF_RTL_EXPR(US_PLUS, "us_plus", "ee", RTX_COMM_ARITH)
 /* Operand 0 minus operand 1, with signed saturation.  */
 DEF_RTL_EXPR(SS_MINUS, "ss_minus", "ee", RTX_BIN_ARITH)
 
+/* Negation with signed saturation.  */
+DEF_RTL_EXPR(SS_NEG, "ss_neg", "e", RTX_UNARY)
+
+/* Shift left with signed saturation.  */
+DEF_RTL_EXPR(SS_ASHIFT, "ss_ashift", "ee", RTX_BIN_ARITH)
+
 /* Operand 0 minus operand 1, with unsigned saturation.  */
 DEF_RTL_EXPR(US_MINUS, "us_minus", "ee", RTX_BIN_ARITH)
 

gcc/simplify-rtx.c

@@ -1092,6 +1092,7 @@ simplify_const_unary_operation (enum rtx_code code, enum machine_mode mode,
 	case FLOAT_TRUNCATE:
 	case SS_TRUNCATE:
 	case US_TRUNCATE:
+	case SS_NEG:
 	  return 0;
 
 	default:
@@ -2422,6 +2423,7 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
       /* Fall through....  */
 
     case ASHIFT:
+    case SS_ASHIFT:
     case LSHIFTRT:
       if (trueop1 == CONST0_RTX (mode))
 	return op0;
@@ -3110,6 +3112,7 @@ simplify_const_binary_operation (enum rtx_code code, enum machine_mode mode,
 	case US_PLUS:
 	case SS_MINUS:
 	case US_MINUS:
+	case SS_ASHIFT:
 	  /* ??? There are simplifications that can be done.  */
 	  return 0;