Issue147 operator rshift

src/sysc/datatypes/int/sc_bigint_inlines.h

@@ -487,34 +487,12 @@ sc_bigint<W>::operator>>(int v) const
     if (v <= 0) {
         return sc_signed(*this);
     }
-    int nb = W - v;
 
-    // If we shift off the end return the sign bit.
+    // Preserve full width W in the result (IEEE 1666-2023 §7.2.8).
 
-    if ( 0 >= nb ) {
-	sc_signed result(1, false);
-        result.digit[0] = 0 > (int)digit[HOD] ? -1 : 0;
-	return result;
-    }
-
-    // Return a value that is the width of the shifted value:
-
-    sc_signed result(nb, false);
-    if ( W < 33 ) {
-	result.digit[0] = (int)digit[0] >> v;
-    }
-    else if ( W < 65 ) {
-        int64 tmp = digit[DIV_CEIL(W)-1];
-        tmp = (tmp << 32) | digit[0];
-	tmp = tmp >> v;
-	result.digit[0] = tmp;
-	if ( nb > 32 ) {
-	    result.digit[1] = (tmp >>32);
-	}
-    }
-    else {
-	vector_extract(digit, result.digit, W-1, v);
-    }
+    sc_signed result(*this);
+    vector_shift_right(result.ndigits, result.digit, v,
+                       (int)digit[HOD] < 0 ? DIGIT_MASK : 0);
     result.adjust_hod();
     return result;
 }

src/sysc/datatypes/int/sc_biguint_inlines.h

@@ -463,37 +463,11 @@ sc_biguint<W>::operator>>(int v) const
     if (v <= 0) {
         return sc_unsigned(*this);
     }
-    int nb = W - v;
 
-    // If we shift off the end return a single bit 0.
+    // Preserve full width W in the result (IEEE 1666-2023 §7.2.8).
 
-    if ( nb <= 0 ) {
-        sc_unsigned result(1, true);
-	return result;
-    }
-
-
-    // Return a value that is the width of the shifted value:
-    //
-    // Note: sc_biguint<W> values have one extra bit on the top, so the comparison is down
-    // one bit, e.g., W < 32, not W < 33.
-
-    sc_unsigned result(nb, false);
-    if ( W < 32 ) {
-	result.digit[0] = digit[0] >> v;
-    }
-    else if ( W < 64 ) {
-        uint64 tmp = digit[DIV_CEIL(W)-1];
-        tmp = (tmp << 32) | digit[0];
-	tmp = tmp >> v;
-	result.digit[0] = tmp;
-	if ( result.nbits > 32 ) { 
-	    result.digit[1] = (tmp >> 32);
-	}
-    }
-    else {
-	vector_extract(digit, result.digit, W-1, v);  
-    }
+    sc_unsigned result(*this);
+    vector_shift_right(result.ndigits, result.digit, v, 0);
     result.adjust_hod();
     return result;
 }

src/sysc/datatypes/int/sc_signed.h

@@ -1075,34 +1075,12 @@ class SC_API sc_signed : public sc_value_base
       if (v <= 0) {
           return sc_signed(*this);
       }
-      int nb = nbits - v;
 
-      // If we shift off the end return the sign bit.
+      // Preserve full width in the result (IEEE 1666-2023 §7.2.8).
 
-      if ( 0 >= nb ) {
-          sc_signed result(1, false);
-          result.digit[0] = 0 > (int)digit[ndigits-1] ? -1 : 0;
-          return result;
-      }
-
-      // Return a value that is the width of the shifted value:
-
-      sc_signed result(nb, false);
-      if ( nbits < 33 ) {
-          result.digit[0] = (int)digit[0] >> v;
-      }
-      else if ( nbits < 65 ) {
-          int64 tmp = digit[1];
-          tmp = (tmp << 32) | digit[0];
-          tmp = tmp >> v;
-          result.digit[0] = (sc_digit)tmp;
-          if ( nb > 32 ) {
-              result.digit[1] = (tmp >>32);
-          }
-      }
-      else {
-          vector_extract(digit, result.digit, nbits-1, v);
-      }
+      sc_signed result(*this);
+      vector_shift_right(result.ndigits, result.digit, v,
+                         (int)digit[ndigits-1] < 0 ? DIGIT_MASK : 0);
       result.adjust_hod();
       return result;
   }

src/sysc/datatypes/int/sc_unsigned.h

@@ -1068,33 +1068,11 @@ class SC_API sc_unsigned : public sc_value_base
       if (v <= 0) {
           return sc_unsigned(*this);
       }
-      int nb = nbits - v;
 
-      // If we shift off the end return the sign bit.
+      // Preserve full width in the result (IEEE 1666-2023 §7.2.8).
 
-      if ( 0 >= nb ) {
-          sc_unsigned result(1, true);
-          return result;
-      }
-
-      // Return a value that is the width of the shifted value:
-
-      sc_unsigned result(nb, false);
-      if ( nbits < 33 ) {
-          result.digit[0] = (int)digit[0] >> v;
-      }
-      else if ( nbits < 65 ) {
-          int64 tmp = digit[1];
-          tmp = (tmp << 32) | digit[0];
-          tmp = tmp >> v;
-          result.digit[0] = (sc_digit)tmp;
-          if ( nb > 32 ) {
-              result.digit[1] = (tmp >>32);
-          }
-      }
-      else {
-          vector_extract(digit, result.digit, nbits-1, v);
-      }
+      sc_unsigned result(*this);
+      vector_shift_right(result.ndigits, result.digit, v, 0);
       result.adjust_hod();
       return result;
   }

tests/systemc/datatypes/int/big_datatypes/shifts/rshift_width/golden/rshift_width.log

@@ -0,0 +1,10 @@
+SystemC Simulation
+sc_bigint<54>(-1048577) >> 32: value=-1 width=54
+sc_bigint<128>(-1) >> 64: value=-1 width=128
+sc_bigint<54>(pos) >> 48: value=0 width=54
+sc_bigint<54>(-1048577) >> 100: value=-1 width=54
+sc_signed(54)(-1048577) >> 32: value=-1 width=54
+sc_biguint<54>(0x3FFFFFFFFF) >> 32: value=63 width=54
+sc_biguint<54>(0x3FFFFFFFFF) >> 100: value=0 width=54
+sc_unsigned(54)(0x3FFFFFFFFF) >> 32: value=63 width=54
+PASSED

tests/systemc/datatypes/int/big_datatypes/shifts/rshift_width/rshift_width.cpp

@@ -0,0 +1,81 @@
+/*****************************************************************************
+
+  Licensed to Accellera Systems Initiative Inc. (Accellera) under one or
+  more contributor license agreements.  See the NOTICE file distributed
+  with this work for additional information regarding copyright ownership.
+  Accellera licenses this file to you under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with the
+  License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+  implied.  See the License for the specific language governing
+  permissions and limitations under the License.
+
+ *****************************************************************************/
+
+// Test that operator>> preserves the result width (IEEE 1666-2023 §7.2.8).
+
+#include "systemc.h"
+
+using std::cout;
+using std::endl;
+
+int sc_main(int, char*[])
+{
+    // --- sc_bigint (signed) ---
+
+    sc_bigint<54> si54 = -1048577;
+    sc_signed     r_si54 = si54 >> 32;
+    cout << "sc_bigint<54>(-1048577) >> 32: value=" << r_si54.to_int64()
+         << " width=" << r_si54.length() << endl;
+
+    sc_bigint<128> si128 = -1;
+    sc_signed      r_si128 = si128 >> 64;
+    cout << "sc_bigint<128>(-1) >> 64: value=" << r_si128.to_int64()
+         << " width=" << r_si128.length() << endl;
+
+    sc_bigint<54> si54z = 0x3FFFFF00000LL;
+    sc_signed     r_si54z = si54z >> 48;
+    cout << "sc_bigint<54>(pos) >> 48: value=" << r_si54z.to_int64()
+         << " width=" << r_si54z.length() << endl;
+
+    // shift >= width
+    sc_signed r_si54_full = si54 >> 100;
+    cout << "sc_bigint<54>(-1048577) >> 100: value=" << r_si54_full.to_int64()
+         << " width=" << r_si54_full.length() << endl;
+
+    // --- sc_signed ---
+
+    sc_signed ss(54);
+    ss = -1048577;
+    sc_signed r_ss = ss >> 32;
+    cout << "sc_signed(54)(-1048577) >> 32: value=" << r_ss.to_int64()
+         << " width=" << r_ss.length() << endl;
+
+    // --- sc_biguint (unsigned) ---
+
+    sc_biguint<54> ui54 = 0x3FFFFFFFFFLL;
+    sc_unsigned    r_ui54 = ui54 >> 32;
+    cout << "sc_biguint<54>(0x3FFFFFFFFF) >> 32: value=" << r_ui54.to_int64()
+         << " width=" << r_ui54.length() << endl;
+
+    // shift >= width
+    sc_unsigned r_ui54_full = ui54 >> 100;
+    cout << "sc_biguint<54>(0x3FFFFFFFFF) >> 100: value=" << r_ui54_full.to_int64()
+         << " width=" << r_ui54_full.length() << endl;
+
+    // --- sc_unsigned ---
+
+    sc_unsigned su(54);
+    su = 0x3FFFFFFFFFLL;
+    sc_unsigned r_su = su >> 32;
+    cout << "sc_unsigned(54)(0x3FFFFFFFFF) >> 32: value=" << r_su.to_int64()
+         << " width=" << r_su.length() << endl;
+
+    cout << "PASSED" << endl;
+    return 0;
+}