Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 1997-2008 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 // Portions of code courtesy of Clifford Click

 #include "incls/_precompiled.incl"

 #include "incls/_mulnode.cpp.incl"

 //=============================================================================

 //------------------------------hash-------------------------------------------

 // Hash function over MulNodes.  Needs to be commutative; i.e., I swap

 // (commute) inputs to MulNodes willy-nilly so the hash function must return

 // the same value in the presence of edge swapping.

 uint MulNode::hash() const {

   return (uintptr_t)in(1) + (uintptr_t)in(2) + Opcode();

 }

 //------------------------------Identity---------------------------------------

 // Multiplying a one preserves the other argument

 Node *MulNode::Identity( PhaseTransform *phase ) {

   register const Type *one = mul_id();  // The multiplicative identity

   if( phase->type( in(1) )->higher_equal( one ) ) return in(2);

   if( phase->type( in(2) )->higher_equal( one ) ) return in(1);

   return this;

 }

 //------------------------------Ideal------------------------------------------

 // We also canonicalize the Node, moving constants to the right input,

 // and flatten expressions (so that 1+x+2 becomes x+3).

 Node *MulNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   Node *progress = NULL;        // Progress flag

   // We are OK if right is a constant, or right is a load and

   // left is a non-constant.

   if( !(t2->singleton() ||

         (in(2)->is_Load() && !(t1->singleton() || in(1)->is_Load())) ) ) {

     if( t1->singleton() ||       // Left input is a constant?

         // Otherwise, sort inputs (commutativity) to help value numbering.

         (in(1)->_idx > in(2)->_idx) ) {

       swap_edges(1, 2);

       const Type *t = t1;

       t1 = t2;

       t2 = t;

       progress = this;            // Made progress

     }

   }

   // If the right input is a constant, and the left input is a product of a

   // constant, flatten the expression tree.

   uint op = Opcode();

   if( t2->singleton() &&        // Right input is a constant?

       op != Op_MulF &&          // Float & double cannot reassociate

       op != Op_MulD ) {

     if( t2 == Type::TOP ) return NULL;

     Node *mul1 = in(1);

 #ifdef ASSERT

     // Check for dead loop

     int   op1 = mul1->Opcode();

     if( phase->eqv( mul1, this ) || phase->eqv( in(2), this ) ||

         ( op1 == mul_opcode() || op1 == add_opcode() ) &&

         ( phase->eqv( mul1->in(1), this ) || phase->eqv( mul1->in(2), this ) ||

           phase->eqv( mul1->in(1), mul1 ) || phase->eqv( mul1->in(2), mul1 ) ) )

       assert(false, "dead loop in MulNode::Ideal");

 #endif

     if( mul1->Opcode() == mul_opcode() ) {  // Left input is a multiply?

       // Mul of a constant?

       const Type *t12 = phase->type( mul1->in(2) );

       if( t12->singleton() && t12 != Type::TOP) { // Left input is an add of a constant?

         // Compute new constant; check for overflow

         const Type *tcon01 = mul1->as_Mul()->mul_ring(t2,t12);

         if( tcon01->singleton() ) {

           // The Mul of the flattened expression

           set_req(1, mul1->in(1));

           set_req(2, phase->makecon( tcon01 ));

           t2 = tcon01;

           progress = this;      // Made progress

         }

       }

     }

     // If the right input is a constant, and the left input is an add of a

     // constant, flatten the tree: (X+con1)*con0 ==> X*con0 + con1*con0

     const Node *add1 = in(1);

     if( add1->Opcode() == add_opcode() ) {      // Left input is an add?

       // Add of a constant?

       const Type *t12 = phase->type( add1->in(2) );

       if( t12->singleton() && t12 != Type::TOP ) { // Left input is an add of a constant?

         assert( add1->in(1) != add1, "dead loop in MulNode::Ideal" );

         // Compute new constant; check for overflow

         const Type *tcon01 = mul_ring(t2,t12);

         if( tcon01->singleton() ) {

         // Convert (X+con1)*con0 into X*con0

           Node *mul = clone();    // mul = ()*con0

           mul->set_req(1,add1->in(1));  // mul = X*con0

           mul = phase->transform(mul);

           Node *add2 = add1->clone();

           add2->set_req(1, mul);        // X*con0 + con0*con1

           add2->set_req(2, phase->makecon(tcon01) );

           progress = add2;

         }

       }

     } // End of is left input an add

   } // End of is right input a Mul

   return progress;

 }

 //------------------------------Value-----------------------------------------

 const Type *MulNode::Value( PhaseTransform *phase ) const {

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   // Either input is TOP ==> the result is TOP

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Either input is ZERO ==> the result is ZERO.

   // Not valid for floats or doubles since +0.0 * -0.0 --> +0.0

   int op = Opcode();

   if( op == Op_MulI || op == Op_AndI || op == Op_MulL || op == Op_AndL ) {

     const Type *zero = add_id();        // The multiplicative zero

     if( t1->higher_equal( zero ) ) return zero;

     if( t2->higher_equal( zero ) ) return zero;

   }

   // Either input is BOTTOM ==> the result is the local BOTTOM

   if( t1 == Type::BOTTOM || t2 == Type::BOTTOM )

     return bottom_type();

   return mul_ring(t1,t2);            // Local flavor of type multiplication

 }

 //=============================================================================

 //------------------------------Ideal------------------------------------------

 // Check for power-of-2 multiply, then try the regular MulNode::Ideal

 Node *MulINode::Ideal(PhaseGVN *phase, bool can_reshape) {

   // Swap constant to right

   jint con;

   if ((con = in(1)->find_int_con(0)) != 0) {

     swap_edges(1, 2);

     // Finish rest of method to use info in 'con'

   } else if ((con = in(2)->find_int_con(0)) == 0) {

     return MulNode::Ideal(phase, can_reshape);

   }

   // Now we have a constant Node on the right and the constant in con

   if( con == 0 ) return NULL;   // By zero is handled by Value call

   if( con == 1 ) return NULL;   // By one  is handled by Identity call

   // Check for negative constant; if so negate the final result

   bool sign_flip = false;

   if( con < 0 ) {

     con = -con;

     sign_flip = true;

   }

   // Get low bit; check for being the only bit

   Node *res = NULL;

   jint bit1 = con & -con;       // Extract low bit

   if( bit1 == con ) {           // Found a power of 2?

     res = new (phase->C, 3) LShiftINode( in(1), phase->intcon(log2_intptr(bit1)) );

   } else {

     // Check for constant with 2 bits set

     jint bit2 = con-bit1;

     bit2 = bit2 & -bit2;          // Extract 2nd bit

     if( bit2 + bit1 == con ) {    // Found all bits in con?

       Node *n1 = phase->transform( new (phase->C, 3) LShiftINode( in(1), phase->intcon(log2_intptr(bit1)) ) );

       Node *n2 = phase->transform( new (phase->C, 3) LShiftINode( in(1), phase->intcon(log2_intptr(bit2)) ) );

       res = new (phase->C, 3) AddINode( n2, n1 );

     } else if (is_power_of_2(con+1)) {

       // Sleezy: power-of-2 -1.  Next time be generic.

       jint temp = (jint) (con + 1);

       Node *n1 = phase->transform( new (phase->C, 3) LShiftINode( in(1), phase->intcon(log2_intptr(temp)) ) );

       res = new (phase->C, 3) SubINode( n1, in(1) );

     } else {

       return MulNode::Ideal(phase, can_reshape);

     }

   }

   if( sign_flip ) {             // Need to negate result?

     res = phase->transform(res);// Transform, before making the zero con

     res = new (phase->C, 3) SubINode(phase->intcon(0),res);

   }

   return res;                   // Return final result

 }

 //------------------------------mul_ring---------------------------------------

 // Compute the product type of two integer ranges into this node.

 const Type *MulINode::mul_ring(const Type *t0, const Type *t1) const {

   const TypeInt *r0 = t0->is_int(); // Handy access

   const TypeInt *r1 = t1->is_int();

   // Fetch endpoints of all ranges

   int32 lo0 = r0->_lo;

   double a = (double)lo0;

   int32 hi0 = r0->_hi;

   double b = (double)hi0;

   int32 lo1 = r1->_lo;

   double c = (double)lo1;

   int32 hi1 = r1->_hi;

   double d = (double)hi1;

   // Compute all endpoints & check for overflow

   int32 A = lo0*lo1;

   if( (double)A != a*c ) return TypeInt::INT; // Overflow?

   int32 B = lo0*hi1;

   if( (double)B != a*d ) return TypeInt::INT; // Overflow?

   int32 C = hi0*lo1;

   if( (double)C != b*c ) return TypeInt::INT; // Overflow?

   int32 D = hi0*hi1;

   if( (double)D != b*d ) return TypeInt::INT; // Overflow?

   if( A < B ) { lo0 = A; hi0 = B; } // Sort range endpoints

   else { lo0 = B; hi0 = A; }

   if( C < D ) {

     if( C < lo0 ) lo0 = C;

     if( D > hi0 ) hi0 = D;

   } else {

     if( D < lo0 ) lo0 = D;

     if( C > hi0 ) hi0 = C;

   }

   return TypeInt::make(lo0, hi0, MAX2(r0->_widen,r1->_widen));

 }

 //=============================================================================

 //------------------------------Ideal------------------------------------------

 // Check for power-of-2 multiply, then try the regular MulNode::Ideal

 Node *MulLNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   // Swap constant to right

   jlong con;

   if ((con = in(1)->find_long_con(0)) != 0) {

     swap_edges(1, 2);

     // Finish rest of method to use info in 'con'

   } else if ((con = in(2)->find_long_con(0)) == 0) {

     return MulNode::Ideal(phase, can_reshape);

   }

   // Now we have a constant Node on the right and the constant in con

   if( con == CONST64(0) ) return NULL;  // By zero is handled by Value call

   if( con == CONST64(1) ) return NULL;  // By one  is handled by Identity call

   // Check for negative constant; if so negate the final result

   bool sign_flip = false;

   if( con < 0 ) {

     con = -con;

     sign_flip = true;

   }

   // Get low bit; check for being the only bit

   Node *res = NULL;

   jlong bit1 = con & -con;      // Extract low bit

   if( bit1 == con ) {           // Found a power of 2?

     res = new (phase->C, 3) LShiftLNode( in(1), phase->intcon(log2_long(bit1)) );

   } else {

     // Check for constant with 2 bits set

     jlong bit2 = con-bit1;

     bit2 = bit2 & -bit2;          // Extract 2nd bit

     if( bit2 + bit1 == con ) {    // Found all bits in con?

       Node *n1 = phase->transform( new (phase->C, 3) LShiftLNode( in(1), phase->intcon(log2_long(bit1)) ) );

       Node *n2 = phase->transform( new (phase->C, 3) LShiftLNode( in(1), phase->intcon(log2_long(bit2)) ) );

       res = new (phase->C, 3) AddLNode( n2, n1 );

     } else if (is_power_of_2_long(con+1)) {

       // Sleezy: power-of-2 -1.  Next time be generic.

       jlong temp = (jlong) (con + 1);

       Node *n1 = phase->transform( new (phase->C, 3) LShiftLNode( in(1), phase->intcon(log2_long(temp)) ) );

       res = new (phase->C, 3) SubLNode( n1, in(1) );

     } else {

       return MulNode::Ideal(phase, can_reshape);

     }

   }

   if( sign_flip ) {             // Need to negate result?

     res = phase->transform(res);// Transform, before making the zero con

     res = new (phase->C, 3) SubLNode(phase->longcon(0),res);

   }

   return res;                   // Return final result

 }

 //------------------------------mul_ring---------------------------------------

 // Compute the product type of two integer ranges into this node.

 const Type *MulLNode::mul_ring(const Type *t0, const Type *t1) const {

   const TypeLong *r0 = t0->is_long(); // Handy access

   const TypeLong *r1 = t1->is_long();

   // Fetch endpoints of all ranges

   jlong lo0 = r0->_lo;

   double a = (double)lo0;

   jlong hi0 = r0->_hi;

   double b = (double)hi0;

   jlong lo1 = r1->_lo;

   double c = (double)lo1;

   jlong hi1 = r1->_hi;

   double d = (double)hi1;

   // Compute all endpoints & check for overflow

   jlong A = lo0*lo1;

   if( (double)A != a*c ) return TypeLong::LONG; // Overflow?

   jlong B = lo0*hi1;

   if( (double)B != a*d ) return TypeLong::LONG; // Overflow?

   jlong C = hi0*lo1;

   if( (double)C != b*c ) return TypeLong::LONG; // Overflow?

   jlong D = hi0*hi1;

   if( (double)D != b*d ) return TypeLong::LONG; // Overflow?

   if( A < B ) { lo0 = A; hi0 = B; } // Sort range endpoints

   else { lo0 = B; hi0 = A; }

   if( C < D ) {

     if( C < lo0 ) lo0 = C;

     if( D > hi0 ) hi0 = D;

   } else {

     if( D < lo0 ) lo0 = D;

     if( C > hi0 ) hi0 = C;

   }

   return TypeLong::make(lo0, hi0, MAX2(r0->_widen,r1->_widen));

 }

 //=============================================================================

 //------------------------------mul_ring---------------------------------------

 // Compute the product type of two double ranges into this node.

 const Type *MulFNode::mul_ring(const Type *t0, const Type *t1) const {

   if( t0 == Type::FLOAT || t1 == Type::FLOAT ) return Type::FLOAT;

   return TypeF::make( t0->getf() * t1->getf() );

 }

 //=============================================================================

 //------------------------------mul_ring---------------------------------------

 // Compute the product type of two double ranges into this node.

 const Type *MulDNode::mul_ring(const Type *t0, const Type *t1) const {

   if( t0 == Type::DOUBLE || t1 == Type::DOUBLE ) return Type::DOUBLE;

   // We must be adding 2 double constants.

   return TypeD::make( t0->getd() * t1->getd() );

 }

 //=============================================================================

 //------------------------------Value------------------------------------------

 const Type *MulHiLNode::Value( PhaseTransform *phase ) const {

   // Either input is TOP ==> the result is TOP

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Either input is BOTTOM ==> the result is the local BOTTOM

   const Type *bot = bottom_type();

   if( (t1 == bot) || (t2 == bot) ||

       (t1 == Type::BOTTOM) || (t2 == Type::BOTTOM) )

     return bot;

   // It is not worth trying to constant fold this stuff!

   return TypeLong::LONG;

 }

 //=============================================================================

 //------------------------------mul_ring---------------------------------------

 // Supplied function returns the product of the inputs IN THE CURRENT RING.

 // For the logical operations the ring's MUL is really a logical AND function.

 // This also type-checks the inputs for sanity.  Guaranteed never to

 // be passed a TOP or BOTTOM type, these are filtered out by pre-check.

 const Type *AndINode::mul_ring( const Type *t0, const Type *t1 ) const {

   const TypeInt *r0 = t0->is_int(); // Handy access

   const TypeInt *r1 = t1->is_int();

   int widen = MAX2(r0->_widen,r1->_widen);

   // If either input is a constant, might be able to trim cases

   if( !r0->is_con() && !r1->is_con() )

     return TypeInt::INT;        // No constants to be had

   // Both constants?  Return bits

   if( r0->is_con() && r1->is_con() )

     return TypeInt::make( r0->get_con() & r1->get_con() );

   if( r0->is_con() && r0->get_con() > 0 )

     return TypeInt::make(0, r0->get_con(), widen);

   if( r1->is_con() && r1->get_con() > 0 )

     return TypeInt::make(0, r1->get_con(), widen);

   if( r0 == TypeInt::BOOL || r1 == TypeInt::BOOL ) {

     return TypeInt::BOOL;

   }

   return TypeInt::INT;          // No constants to be had

 }

 //------------------------------Identity---------------------------------------

 // Masking off the high bits of an unsigned load is not required

 Node *AndINode::Identity( PhaseTransform *phase ) {

   // x & x => x

   if (phase->eqv(in(1), in(2))) return in(1);

   Node *load = in(1);

   const TypeInt *t2 = phase->type( in(2) )->isa_int();

   if( t2 && t2->is_con() ) {

     int con = t2->get_con();

     // Masking off high bits which are always zero is useless.

     const TypeInt* t1 = phase->type( in(1) )->isa_int();

     if (t1 != NULL && t1->_lo >= 0) {

       jint t1_support = ((jint)1 << (1 + log2_intptr(t1->_hi))) - 1;

       if ((t1_support & con) == t1_support)

         return load;

     }

     uint lop = load->Opcode();

     if( lop == Op_LoadC &&

         con == 0x0000FFFF )     // Already zero-extended

       return load;

     // Masking off the high bits of a unsigned-shift-right is not

     // needed either.

     if( lop == Op_URShiftI ) {

       const TypeInt *t12 = phase->type( load->in(2) )->isa_int();

       if( t12 && t12->is_con() ) {

         int shift_con = t12->get_con();

         int mask = max_juint >> shift_con;

         if( (mask&con) == mask )  // If AND is useless, skip it

           return load;

       }

     }

   }

   return MulNode::Identity(phase);

 }

 //------------------------------Ideal------------------------------------------

 Node *AndINode::Ideal(PhaseGVN *phase, bool can_reshape) {

   // Special case constant AND mask

   const TypeInt *t2 = phase->type( in(2) )->isa_int();

   if( !t2 || !t2->is_con() ) return MulNode::Ideal(phase, can_reshape);

   const int mask = t2->get_con();

   Node *load = in(1);

   uint lop = load->Opcode();

   // Masking bits off of a Character?  Hi bits are already zero.

   if( lop == Op_LoadC &&

       (mask & 0xFFFF0000) )     // Can we make a smaller mask?

     return new (phase->C, 3) AndINode(load,phase->intcon(mask&0xFFFF));

   // Masking bits off of a Short?  Loading a Character does some masking

   if( lop == Op_LoadS &&

       (mask & 0xFFFF0000) == 0 ) {

     Node *ldc = new (phase->C, 3) LoadCNode(load->in(MemNode::Control),

                                   load->in(MemNode::Memory),

                                   load->in(MemNode::Address),

                                   load->adr_type());

     ldc = phase->transform(ldc);

     return new (phase->C, 3) AndINode(ldc,phase->intcon(mask&0xFFFF));

   }

   // Masking sign bits off of a Byte?  Let the matcher use an unsigned load

   if( lop == Op_LoadB &&

       (!in(0) && load->in(0)) &&

       (mask == 0x000000FF) ) {

     // Associate this node with the LoadB, so the matcher can see them together.

     // If we don't do this, it is common for the LoadB to have one control

     // edge, and the store or call containing this AndI to have a different

     // control edge.  This will cause Label_Root to group the AndI with

     // the encoding store or call, so the matcher has no chance to match

     // this AndI together with the LoadB.  Setting the control edge here

     // prevents Label_Root from grouping the AndI with the store or call,

     // if it has a control edge that is inconsistent with the LoadB.

     set_req(0, load->in(0));

     return this;

   }

   // Masking off sign bits?  Dont make them!

   if( lop == Op_RShiftI ) {

     const TypeInt *t12 = phase->type(load->in(2))->isa_int();

     if( t12 && t12->is_con() ) { // Shift is by a constant

       int shift = t12->get_con();

       shift &= BitsPerJavaInteger-1;  // semantics of Java shifts

       const int sign_bits_mask = ~right_n_bits(BitsPerJavaInteger - shift);

       // If the AND'ing of the 2 masks has no bits, then only original shifted

       // bits survive.  NO sign-extension bits survive the maskings.

       if( (sign_bits_mask & mask) == 0 ) {

         // Use zero-fill shift instead

         Node *zshift = phase->transform(new (phase->C, 3) URShiftINode(load->in(1),load->in(2)));

         return new (phase->C, 3) AndINode( zshift, in(2) );

       }

     }

   }

   // Check for 'negate/and-1', a pattern emitted when someone asks for

   // 'mod 2'.  Negate leaves the low order bit unchanged (think: complement

   // plus 1) and the mask is of the low order bit.  Skip the negate.

   if( lop == Op_SubI && mask == 1 && load->in(1) &&

       phase->type(load->in(1)) == TypeInt::ZERO )

     return new (phase->C, 3) AndINode( load->in(2), in(2) );

   return MulNode::Ideal(phase, can_reshape);

 }

 //=============================================================================

 //------------------------------mul_ring---------------------------------------

 // Supplied function returns the product of the inputs IN THE CURRENT RING.

 // For the logical operations the ring's MUL is really a logical AND function.

 // This also type-checks the inputs for sanity.  Guaranteed never to

 // be passed a TOP or BOTTOM type, these are filtered out by pre-check.

 const Type *AndLNode::mul_ring( const Type *t0, const Type *t1 ) const {

   const TypeLong *r0 = t0->is_long(); // Handy access

   const TypeLong *r1 = t1->is_long();

   int widen = MAX2(r0->_widen,r1->_widen);

   // If either input is a constant, might be able to trim cases

   if( !r0->is_con() && !r1->is_con() )

     return TypeLong::LONG;      // No constants to be had

   // Both constants?  Return bits

   if( r0->is_con() && r1->is_con() )

     return TypeLong::make( r0->get_con() & r1->get_con() );

   if( r0->is_con() && r0->get_con() > 0 )

     return TypeLong::make(CONST64(0), r0->get_con(), widen);

   if( r1->is_con() && r1->get_con() > 0 )

     return TypeLong::make(CONST64(0), r1->get_con(), widen);

   return TypeLong::LONG;        // No constants to be had

 }

 //------------------------------Identity---------------------------------------

 // Masking off the high bits of an unsigned load is not required

 Node *AndLNode::Identity( PhaseTransform *phase ) {

   // x & x => x

   if (phase->eqv(in(1), in(2))) return in(1);

   Node *usr = in(1);

   const TypeLong *t2 = phase->type( in(2) )->isa_long();

   if( t2 && t2->is_con() ) {

     jlong con = t2->get_con();

     // Masking off high bits which are always zero is useless.

     const TypeLong* t1 = phase->type( in(1) )->isa_long();

     if (t1 != NULL && t1->_lo >= 0) {

       jlong t1_support = ((jlong)1 << (1 + log2_long(t1->_hi))) - 1;

       if ((t1_support & con) == t1_support)

         return usr;

     }

     uint lop = usr->Opcode();

     // Masking off the high bits of a unsigned-shift-right is not

     // needed either.

     if( lop == Op_URShiftL ) {

       const TypeInt *t12 = phase->type( usr->in(2) )->isa_int();

       if( t12 && t12->is_con() ) {

         int shift_con = t12->get_con();

         jlong mask = max_julong >> shift_con;

         if( (mask&con) == mask )  // If AND is useless, skip it

           return usr;

       }

     }

   }

   return MulNode::Identity(phase);

 }

 //------------------------------Ideal------------------------------------------

 Node *AndLNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   // Special case constant AND mask

   const TypeLong *t2 = phase->type( in(2) )->isa_long();

   if( !t2 || !t2->is_con() ) return MulNode::Ideal(phase, can_reshape);

   const jlong mask = t2->get_con();

   Node *rsh = in(1);

   uint rop = rsh->Opcode();

   // Masking off sign bits?  Dont make them!

   if( rop == Op_RShiftL ) {

     const TypeInt *t12 = phase->type(rsh->in(2))->isa_int();

     if( t12 && t12->is_con() ) { // Shift is by a constant

       int shift = t12->get_con();

       shift &= (BitsPerJavaInteger*2)-1;  // semantics of Java shifts

       const jlong sign_bits_mask = ~(((jlong)CONST64(1) << (jlong)(BitsPerJavaInteger*2 - shift)) -1);

       // If the AND'ing of the 2 masks has no bits, then only original shifted

       // bits survive.  NO sign-extension bits survive the maskings.

       if( (sign_bits_mask & mask) == 0 ) {

         // Use zero-fill shift instead

         Node *zshift = phase->transform(new (phase->C, 3) URShiftLNode(rsh->in(1),rsh->in(2)));

         return new (phase->C, 3) AndLNode( zshift, in(2) );

       }

     }

   }

   return MulNode::Ideal(phase, can_reshape);

 }

 //=============================================================================

 //------------------------------Identity---------------------------------------

 Node *LShiftINode::Identity( PhaseTransform *phase ) {

   const TypeInt *ti = phase->type( in(2) )->isa_int();  // shift count is an int

   return ( ti && ti->is_con() && ( ti->get_con() & ( BitsPerInt - 1 ) ) == 0 ) ? in(1) : this;

 }

 //------------------------------Ideal------------------------------------------

 // If the right input is a constant, and the left input is an add of a

 // constant, flatten the tree: (X+con1)<<con0 ==> X<<con0 + con1<<con0

 Node *LShiftINode::Ideal(PhaseGVN *phase, bool can_reshape) {

   const Type *t  = phase->type( in(2) );

   if( t == Type::TOP ) return NULL;       // Right input is dead

   const TypeInt *t2 = t->isa_int();

   if( !t2 || !t2->is_con() ) return NULL; // Right input is a constant

   const int con = t2->get_con() & ( BitsPerInt - 1 );  // masked shift count

   if ( con == 0 )  return NULL; // let Identity() handle 0 shift count

   // Left input is an add of a constant?

   Node *add1 = in(1);

   int add1_op = add1->Opcode();

   if( add1_op == Op_AddI ) {    // Left input is an add?

     assert( add1 != add1->in(1), "dead loop in LShiftINode::Ideal" );

     const TypeInt *t12 = phase->type(add1->in(2))->isa_int();

     if( t12 && t12->is_con() ){ // Left input is an add of a con?

       // Transform is legal, but check for profit.  Avoid breaking 'i2s'

       // and 'i2b' patterns which typically fold into 'StoreC/StoreB'.

       if( con < 16 ) {

         // Compute X << con0

         Node *lsh = phase->transform( new (phase->C, 3) LShiftINode( add1->in(1), in(2) ) );

         // Compute X<<con0 + (con1<<con0)

         return new (phase->C, 3) AddINode( lsh, phase->intcon(t12->get_con() << con));

       }

     }

   }

   // Check for "(x>>c0)<<c0" which just masks off low bits

   if( (add1_op == Op_RShiftI || add1_op == Op_URShiftI ) &&

       add1->in(2) == in(2) )

     // Convert to "(x & -(1<<c0))"

     return new (phase->C, 3) AndINode(add1->in(1),phase->intcon( -(1<<con)));

   // Check for "((x>>c0) & Y)<<c0" which just masks off more low bits

   if( add1_op == Op_AndI ) {

     Node *add2 = add1->in(1);

     int add2_op = add2->Opcode();

     if( (add2_op == Op_RShiftI || add2_op == Op_URShiftI ) &&

         add2->in(2) == in(2) ) {

       // Convert to "(x & (Y<<c0))"

       Node *y_sh = phase->transform( new (phase->C, 3) LShiftINode( add1->in(2), in(2) ) );

       return new (phase->C, 3) AndINode( add2->in(1), y_sh );

     }

   }

   // Check for ((x & ((1<<(32-c0))-1)) << c0) which ANDs off high bits

   // before shifting them away.

   const jint bits_mask = right_n_bits(BitsPerJavaInteger-con);

   if( add1_op == Op_AndI &&

       phase->type(add1->in(2)) == TypeInt::make( bits_mask ) )

     return new (phase->C, 3) LShiftINode( add1->in(1), in(2) );

   return NULL;

 }

 //------------------------------Value------------------------------------------

 // A LShiftINode shifts its input2 left by input1 amount.

 const Type *LShiftINode::Value( PhaseTransform *phase ) const {

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   // Either input is TOP ==> the result is TOP

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Left input is ZERO ==> the result is ZERO.

   if( t1 == TypeInt::ZERO ) return TypeInt::ZERO;

   // Shift by zero does nothing

   if( t2 == TypeInt::ZERO ) return t1;

   // Either input is BOTTOM ==> the result is BOTTOM

   if( (t1 == TypeInt::INT) || (t2 == TypeInt::INT) ||

       (t1 == Type::BOTTOM) || (t2 == Type::BOTTOM) )

     return TypeInt::INT;

   const TypeInt *r1 = t1->is_int(); // Handy access

   const TypeInt *r2 = t2->is_int(); // Handy access

   if (!r2->is_con())

     return TypeInt::INT;

   uint shift = r2->get_con();

   shift &= BitsPerJavaInteger-1;  // semantics of Java shifts

   // Shift by a multiple of 32 does nothing:

   if (shift == 0)  return t1;

   // If the shift is a constant, shift the bounds of the type,

   // unless this could lead to an overflow.

   if (!r1->is_con()) {

     jint lo = r1->_lo, hi = r1->_hi;

     if (((lo << shift) >> shift) == lo &&

         ((hi << shift) >> shift) == hi) {

       // No overflow.  The range shifts up cleanly.

       return TypeInt::make((jint)lo << (jint)shift,

                            (jint)hi << (jint)shift,

                            MAX2(r1->_widen,r2->_widen));

     }

     return TypeInt::INT;

   }

   return TypeInt::make( (jint)r1->get_con() << (jint)shift );

 }

 //=============================================================================

 //------------------------------Identity---------------------------------------

 Node *LShiftLNode::Identity( PhaseTransform *phase ) {

   const TypeInt *ti = phase->type( in(2) )->isa_int(); // shift count is an int

   return ( ti && ti->is_con() && ( ti->get_con() & ( BitsPerLong - 1 ) ) == 0 ) ? in(1) : this;

 }

 //------------------------------Ideal------------------------------------------

 // If the right input is a constant, and the left input is an add of a

 // constant, flatten the tree: (X+con1)<<con0 ==> X<<con0 + con1<<con0

 Node *LShiftLNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   const Type *t  = phase->type( in(2) );

   if( t == Type::TOP ) return NULL;       // Right input is dead

   const TypeInt *t2 = t->isa_int();

   if( !t2 || !t2->is_con() ) return NULL; // Right input is a constant

   const int con = t2->get_con() & ( BitsPerLong - 1 );  // masked shift count

   if ( con == 0 ) return NULL;  // let Identity() handle 0 shift count

   // Left input is an add of a constant?

   Node *add1 = in(1);

   int add1_op = add1->Opcode();

   if( add1_op == Op_AddL ) {    // Left input is an add?

     // Avoid dead data cycles from dead loops

     assert( add1 != add1->in(1), "dead loop in LShiftLNode::Ideal" );

     const TypeLong *t12 = phase->type(add1->in(2))->isa_long();

     if( t12 && t12->is_con() ){ // Left input is an add of a con?

       // Compute X << con0

       Node *lsh = phase->transform( new (phase->C, 3) LShiftLNode( add1->in(1), in(2) ) );

       // Compute X<<con0 + (con1<<con0)

       return new (phase->C, 3) AddLNode( lsh, phase->longcon(t12->get_con() << con));

     }

   }

   // Check for "(x>>c0)<<c0" which just masks off low bits

   if( (add1_op == Op_RShiftL || add1_op == Op_URShiftL ) &&

       add1->in(2) == in(2) )

     // Convert to "(x & -(1<<c0))"

     return new (phase->C, 3) AndLNode(add1->in(1),phase->longcon( -(CONST64(1)<<con)));

   // Check for "((x>>c0) & Y)<<c0" which just masks off more low bits

   if( add1_op == Op_AndL ) {

     Node *add2 = add1->in(1);

     int add2_op = add2->Opcode();

     if( (add2_op == Op_RShiftL || add2_op == Op_URShiftL ) &&

         add2->in(2) == in(2) ) {

       // Convert to "(x & (Y<<c0))"

       Node *y_sh = phase->transform( new (phase->C, 3) LShiftLNode( add1->in(2), in(2) ) );

       return new (phase->C, 3) AndLNode( add2->in(1), y_sh );

     }

   }

   // Check for ((x & ((CONST64(1)<<(64-c0))-1)) << c0) which ANDs off high bits

   // before shifting them away.

   const jlong bits_mask = ((jlong)CONST64(1) << (jlong)(BitsPerJavaInteger*2 - con)) - CONST64(1);

   if( add1_op == Op_AndL &&

       phase->type(add1->in(2)) == TypeLong::make( bits_mask ) )

     return new (phase->C, 3) LShiftLNode( add1->in(1), in(2) );

   return NULL;

 }

 //------------------------------Value------------------------------------------

 // A LShiftLNode shifts its input2 left by input1 amount.

 const Type *LShiftLNode::Value( PhaseTransform *phase ) const {

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   // Either input is TOP ==> the result is TOP

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Left input is ZERO ==> the result is ZERO.

   if( t1 == TypeLong::ZERO ) return TypeLong::ZERO;

   // Shift by zero does nothing

   if( t2 == TypeInt::ZERO ) return t1;

   // Either input is BOTTOM ==> the result is BOTTOM

   if( (t1 == TypeLong::LONG) || (t2 == TypeInt::INT) ||

       (t1 == Type::BOTTOM) || (t2 == Type::BOTTOM) )

     return TypeLong::LONG;

   const TypeLong *r1 = t1->is_long(); // Handy access

   const TypeInt  *r2 = t2->is_int();  // Handy access

   if (!r2->is_con())

     return TypeLong::LONG;

   uint shift = r2->get_con();

   shift &= (BitsPerJavaInteger*2)-1;  // semantics of Java shifts

   // Shift by a multiple of 64 does nothing:

   if (shift == 0)  return t1;

   // If the shift is a constant, shift the bounds of the type,

   // unless this could lead to an overflow.

   if (!r1->is_con()) {

     jlong lo = r1->_lo, hi = r1->_hi;

     if (((lo << shift) >> shift) == lo &&

         ((hi << shift) >> shift) == hi) {

       // No overflow.  The range shifts up cleanly.

       return TypeLong::make((jlong)lo << (jint)shift,

                             (jlong)hi << (jint)shift,

                             MAX2(r1->_widen,r2->_widen));

     }

     return TypeLong::LONG;

   }

   return TypeLong::make( (jlong)r1->get_con() << (jint)shift );

 }

 //=============================================================================

 //------------------------------Identity---------------------------------------

 Node *RShiftINode::Identity( PhaseTransform *phase ) {

   const TypeInt *t2 = phase->type(in(2))->isa_int();

   if( !t2 ) return this;

   if ( t2->is_con() && ( t2->get_con() & ( BitsPerInt - 1 ) ) == 0 )

     return in(1);

   // Check for useless sign-masking

   if( in(1)->Opcode() == Op_LShiftI &&

       in(1)->req() == 3 &&

       in(1)->in(2) == in(2) &&

       t2->is_con() ) {

     uint shift = t2->get_con();

     shift &= BitsPerJavaInteger-1; // semantics of Java shifts

     // Compute masks for which this shifting doesn't change

     int lo = (-1 << (BitsPerJavaInteger - shift-1)); // FFFF8000

     int hi = ~lo;               // 00007FFF

     const TypeInt *t11 = phase->type(in(1)->in(1))->isa_int();

     if( !t11 ) return this;

     // Does actual value fit inside of mask?

     if( lo <= t11->_lo && t11->_hi <= hi )

       return in(1)->in(1);      // Then shifting is a nop

   }

   return this;

 }

 //------------------------------Ideal------------------------------------------

 Node *RShiftINode::Ideal(PhaseGVN *phase, bool can_reshape) {

   // Inputs may be TOP if they are dead.

   const TypeInt *t1 = phase->type( in(1) )->isa_int();

   if( !t1 ) return NULL;        // Left input is an integer

   const TypeInt *t2 = phase->type( in(2) )->isa_int();

   if( !t2 || !t2->is_con() ) return NULL; // Right input is a constant

   const TypeInt *t3;  // type of in(1).in(2)

   int shift = t2->get_con();

   shift &= BitsPerJavaInteger-1;  // semantics of Java shifts

   if ( shift == 0 ) return NULL;  // let Identity() handle 0 shift count

   // Check for (x & 0xFF000000) >> 24, whose mask can be made smaller.

   // Such expressions arise normally from shift chains like (byte)(x >> 24).

   const Node *mask = in(1);

   if( mask->Opcode() == Op_AndI &&

       (t3 = phase->type(mask->in(2))->isa_int()) &&

       t3->is_con() ) {

     Node *x = mask->in(1);

     jint maskbits = t3->get_con();

     // Convert to "(x >> shift) & (mask >> shift)"

     Node *shr_nomask = phase->transform( new (phase->C, 3) RShiftINode(mask->in(1), in(2)) );

     return new (phase->C, 3) AndINode(shr_nomask, phase->intcon( maskbits >> shift));

   }

   // Check for "(short[i] <<16)>>16" which simply sign-extends

   const Node *shl = in(1);

   if( shl->Opcode() != Op_LShiftI ) return NULL;

   if( shift == 16 &&

       (t3 = phase->type(shl->in(2))->isa_int()) &&

       t3->is_con(16) ) {

     Node *ld = shl->in(1);

     if( ld->Opcode() == Op_LoadS ) {

       // Sign extension is just useless here.  Return a RShiftI of zero instead

       // returning 'ld' directly.  We cannot return an old Node directly as

       // that is the job of 'Identity' calls and Identity calls only work on

       // direct inputs ('ld' is an extra Node removed from 'this').  The

       // combined optimization requires Identity only return direct inputs.

       set_req(1, ld);

       set_req(2, phase->intcon(0));

       return this;

     }

     else if( ld->Opcode() == Op_LoadC )

       // Replace zero-extension-load with sign-extension-load

       return new (phase->C, 3) LoadSNode( ld->in(MemNode::Control),

                                 ld->in(MemNode::Memory),

                                 ld->in(MemNode::Address),

                                 ld->adr_type());

   }

   // Check for "(byte[i] <<24)>>24" which simply sign-extends

   if( shift == 24 &&

       (t3 = phase->type(shl->in(2))->isa_int()) &&

       t3->is_con(24) ) {

     Node *ld = shl->in(1);

     if( ld->Opcode() == Op_LoadB ) {

       // Sign extension is just useless here

       set_req(1, ld);

       set_req(2, phase->intcon(0));

       return this;

     }

   }

   return NULL;

 }

 //------------------------------Value------------------------------------------

 // A RShiftINode shifts its input2 right by input1 amount.

 const Type *RShiftINode::Value( PhaseTransform *phase ) const {

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   // Either input is TOP ==> the result is TOP

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Left input is ZERO ==> the result is ZERO.

   if( t1 == TypeInt::ZERO ) return TypeInt::ZERO;

   // Shift by zero does nothing

   if( t2 == TypeInt::ZERO ) return t1;

   // Either input is BOTTOM ==> the result is BOTTOM

   if (t1 == Type::BOTTOM || t2 == Type::BOTTOM)

     return TypeInt::INT;

   if (t2 == TypeInt::INT)

     return TypeInt::INT;

   const TypeInt *r1 = t1->is_int(); // Handy access

   const TypeInt *r2 = t2->is_int(); // Handy access

   // If the shift is a constant, just shift the bounds of the type.

   // For example, if the shift is 31, we just propagate sign bits.

   if (r2->is_con()) {

     uint shift = r2->get_con();

     shift &= BitsPerJavaInteger-1;  // semantics of Java shifts

     // Shift by a multiple of 32 does nothing:

     if (shift == 0)  return t1;

     // Calculate reasonably aggressive bounds for the result.

     // This is necessary if we are to correctly type things

     // like (x<<24>>24) == ((byte)x).

     jint lo = (jint)r1->_lo >> (jint)shift;

     jint hi = (jint)r1->_hi >> (jint)shift;

     assert(lo <= hi, "must have valid bounds");

     const TypeInt* ti = TypeInt::make(lo, hi, MAX2(r1->_widen,r2->_widen));

 #ifdef ASSERT

     // Make sure we get the sign-capture idiom correct.

     if (shift == BitsPerJavaInteger-1) {

       if (r1->_lo >= 0) assert(ti == TypeInt::ZERO,    ">>31 of + is  0");

       if (r1->_hi <  0) assert(ti == TypeInt::MINUS_1, ">>31 of - is -1");

     }

 #endif

     return ti;

   }

   if( !r1->is_con() || !r2->is_con() )

     return TypeInt::INT;

   // Signed shift right

   return TypeInt::make( r1->get_con() >> (r2->get_con()&31) );

 }

 //=============================================================================

 //------------------------------Identity---------------------------------------

 Node *RShiftLNode::Identity( PhaseTransform *phase ) {

   const TypeInt *ti = phase->type( in(2) )->isa_int(); // shift count is an int

   return ( ti && ti->is_con() && ( ti->get_con() & ( BitsPerLong - 1 ) ) == 0 ) ? in(1) : this;

 }

 //------------------------------Value------------------------------------------

 // A RShiftLNode shifts its input2 right by input1 amount.

 const Type *RShiftLNode::Value( PhaseTransform *phase ) const {

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   // Either input is TOP ==> the result is TOP

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Left input is ZERO ==> the result is ZERO.

   if( t1 == TypeLong::ZERO ) return TypeLong::ZERO;

   // Shift by zero does nothing

   if( t2 == TypeInt::ZERO ) return t1;

   // Either input is BOTTOM ==> the result is BOTTOM

   if (t1 == Type::BOTTOM || t2 == Type::BOTTOM)

     return TypeLong::LONG;

   if (t2 == TypeInt::INT)

     return TypeLong::LONG;

   const TypeLong *r1 = t1->is_long(); // Handy access

   const TypeInt  *r2 = t2->is_int (); // Handy access

   // If the shift is a constant, just shift the bounds of the type.

   // For example, if the shift is 63, we just propagate sign bits.

   if (r2->is_con()) {

     uint shift = r2->get_con();

     shift &= (2*BitsPerJavaInteger)-1;  // semantics of Java shifts

     // Shift by a multiple of 64 does nothing:

     if (shift == 0)  return t1;

     // Calculate reasonably aggressive bounds for the result.

     // This is necessary if we are to correctly type things

     // like (x<<24>>24) == ((byte)x).

     jlong lo = (jlong)r1->_lo >> (jlong)shift;

     jlong hi = (jlong)r1->_hi >> (jlong)shift;

     assert(lo <= hi, "must have valid bounds");

     const TypeLong* tl = TypeLong::make(lo, hi, MAX2(r1->_widen,r2->_widen));

     #ifdef ASSERT

     // Make sure we get the sign-capture idiom correct.

     if (shift == (2*BitsPerJavaInteger)-1) {

       if (r1->_lo >= 0) assert(tl == TypeLong::ZERO,    ">>63 of + is 0");

       if (r1->_hi < 0)  assert(tl == TypeLong::MINUS_1, ">>63 of - is -1");

     }

     #endif

     return tl;

   }

   return TypeLong::LONG;                // Give up

 }

 //=============================================================================

 //------------------------------Identity---------------------------------------

 Node *URShiftINode::Identity( PhaseTransform *phase ) {

   const TypeInt *ti = phase->type( in(2) )->isa_int();

   if ( ti && ti->is_con() && ( ti->get_con() & ( BitsPerInt - 1 ) ) == 0 ) return in(1);

   // Check for "((x << LogBytesPerWord) + (wordSize-1)) >> LogBytesPerWord" which is just "x".

   // Happens during new-array length computation.

   // Safe if 'x' is in the range [0..(max_int>>LogBytesPerWord)]

   Node *add = in(1);

   if( add->Opcode() == Op_AddI ) {

     const TypeInt *t2  = phase->type(add->in(2))->isa_int();

     if( t2 && t2->is_con(wordSize - 1) &&

         add->in(1)->Opcode() == Op_LShiftI ) {

       // Check that shift_counts are LogBytesPerWord

       Node          *lshift_count   = add->in(1)->in(2);

       const TypeInt *t_lshift_count = phase->type(lshift_count)->isa_int();

       if( t_lshift_count && t_lshift_count->is_con(LogBytesPerWord) &&

           t_lshift_count == phase->type(in(2)) ) {

         Node          *x   = add->in(1)->in(1);

         const TypeInt *t_x = phase->type(x)->isa_int();

         if( t_x != NULL && 0 <= t_x->_lo && t_x->_hi <= (max_jint>>LogBytesPerWord) ) {

           return x;

         }

       }

     }

   }

   return (phase->type(in(2))->higher_equal(TypeInt::ZERO)) ? in(1) : this;

 }

 //------------------------------Ideal------------------------------------------

 Node *URShiftINode::Ideal(PhaseGVN *phase, bool can_reshape) {

   const TypeInt *t2 = phase->type( in(2) )->isa_int();

   if( !t2 || !t2->is_con() ) return NULL; // Right input is a constant

   const int con = t2->get_con() & 31; // Shift count is always masked

   if ( con == 0 ) return NULL;  // let Identity() handle a 0 shift count

   // We'll be wanting the right-shift amount as a mask of that many bits

   const int mask = right_n_bits(BitsPerJavaInteger - con);

   int in1_op = in(1)->Opcode();

   // Check for ((x>>>a)>>>b) and replace with (x>>>(a+b)) when a+b < 32

   if( in1_op == Op_URShiftI ) {

     const TypeInt *t12 = phase->type( in(1)->in(2) )->isa_int();

     if( t12 && t12->is_con() ) { // Right input is a constant

       assert( in(1) != in(1)->in(1), "dead loop in URShiftINode::Ideal" );

       const int con2 = t12->get_con() & 31; // Shift count is always masked

       const int con3 = con+con2;

       if( con3 < 32 )           // Only merge shifts if total is < 32

         return new (phase->C, 3) URShiftINode( in(1)->in(1), phase->intcon(con3) );

     }

   }

   // Check for ((x << z) + Y) >>> z.  Replace with x + con>>>z

   // The idiom for rounding to a power of 2 is "(Q+(2^z-1)) >>> z".

   // If Q is "X << z" the rounding is useless.  Look for patterns like

   // ((X<<Z) + Y) >>> Z  and replace with (X + Y>>>Z) & Z-mask.

   Node *add = in(1);

   if( in1_op == Op_AddI ) {

     Node *lshl = add->in(1);

     if( lshl->Opcode() == Op_LShiftI &&

         phase->type(lshl->in(2)) == t2 ) {

       Node *y_z = phase->transform( new (phase->C, 3) URShiftINode(add->in(2),in(2)) );

       Node *sum = phase->transform( new (phase->C, 3) AddINode( lshl->in(1), y_z ) );

       return new (phase->C, 3) AndINode( sum, phase->intcon(mask) );

     }

   }

   // Check for (x & mask) >>> z.  Replace with (x >>> z) & (mask >>> z)

   // This shortens the mask.  Also, if we are extracting a high byte and

   // storing it to a buffer, the mask will be removed completely.

   Node *andi = in(1);

   if( in1_op == Op_AndI ) {

     const TypeInt *t3 = phase->type( andi->in(2) )->isa_int();

     if( t3 && t3->is_con() ) { // Right input is a constant

       jint mask2 = t3->get_con();

       mask2 >>= con;  // *signed* shift downward (high-order zeroes do not help)

       Node *newshr = phase->transform( new (phase->C, 3) URShiftINode(andi->in(1), in(2)) );

       return new (phase->C, 3) AndINode(newshr, phase->intcon(mask2));

       // The negative values are easier to materialize than positive ones.

       // A typical case from address arithmetic is ((x & ~15) >> 4).

       // It's better to change that to ((x >> 4) & ~0) versus

       // ((x >> 4) & 0x0FFFFFFF).  The difference is greatest in LP64.

     }

   }

   // Check for "(X << z ) >>> z" which simply zero-extends

   Node *shl = in(1);

   if( in1_op == Op_LShiftI &&

       phase->type(shl->in(2)) == t2 )

     return new (phase->C, 3) AndINode( shl->in(1), phase->intcon(mask) );

   return NULL;

 }

 //------------------------------Value------------------------------------------

 // A URShiftINode shifts its input2 right by input1 amount.

 const Type *URShiftINode::Value( PhaseTransform *phase ) const {

   // (This is a near clone of RShiftINode::Value.)

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   // Either input is TOP ==> the result is TOP

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Left input is ZERO ==> the result is ZERO.

   if( t1 == TypeInt::ZERO ) return TypeInt::ZERO;

   // Shift by zero does nothing

   if( t2 == TypeInt::ZERO ) return t1;

   // Either input is BOTTOM ==> the result is BOTTOM

   if (t1 == Type::BOTTOM || t2 == Type::BOTTOM)

     return TypeInt::INT;

   if (t2 == TypeInt::INT)

     return TypeInt::INT;

   const TypeInt *r1 = t1->is_int();     // Handy access

   const TypeInt *r2 = t2->is_int();     // Handy access

   if (r2->is_con()) {

     uint shift = r2->get_con();

     shift &= BitsPerJavaInteger-1;  // semantics of Java shifts

     // Shift by a multiple of 32 does nothing:

     if (shift == 0)  return t1;

     // Calculate reasonably aggressive bounds for the result.

     jint lo = (juint)r1->_lo >> (juint)shift;

     jint hi = (juint)r1->_hi >> (juint)shift;

     if (r1->_hi >= 0 && r1->_lo < 0) {

       // If the type has both negative and positive values,

       // there are two separate sub-domains to worry about:

       // The positive half and the negative half.

       jint neg_lo = lo;

       jint neg_hi = (juint)-1 >> (juint)shift;

       jint pos_lo = (juint) 0 >> (juint)shift;

       jint pos_hi = hi;

       lo = MIN2(neg_lo, pos_lo);  // == 0

       hi = MAX2(neg_hi, pos_hi);  // == -1 >>> shift;

     }

     assert(lo <= hi, "must have valid bounds");

     const TypeInt* ti = TypeInt::make(lo, hi, MAX2(r1->_widen,r2->_widen));

     #ifdef ASSERT

     // Make sure we get the sign-capture idiom correct.

     if (shift == BitsPerJavaInteger-1) {

       if (r1->_lo >= 0) assert(ti == TypeInt::ZERO, ">>>31 of + is 0");

       if (r1->_hi < 0)  assert(ti == TypeInt::ONE,  ">>>31 of - is +1");

     }

     #endif

     return ti;

   }

   //

   // Do not support shifted oops in info for GC

   //

   // else if( t1->base() == Type::InstPtr ) {

   //

   //   const TypeInstPtr *o = t1->is_instptr();

   //   if( t1->singleton() )

   //     return TypeInt::make( ((uint32)o->const_oop() + o->_offset) >> shift );

   // }

   // else if( t1->base() == Type::KlassPtr ) {

   //   const TypeKlassPtr *o = t1->is_klassptr();

   //   if( t1->singleton() )

   //     return TypeInt::make( ((uint32)o->const_oop() + o->_offset) >> shift );

   // }

   return TypeInt::INT;

 }

 //=============================================================================

 //------------------------------Identity---------------------------------------

 Node *URShiftLNode::Identity( PhaseTransform *phase ) {

   const TypeInt *ti = phase->type( in(2) )->isa_int(); // shift count is an int

   return ( ti && ti->is_con() && ( ti->get_con() & ( BitsPerLong - 1 ) ) == 0 ) ? in(1) : this;

 }

 //------------------------------Ideal------------------------------------------

 Node *URShiftLNode::Ideal(PhaseGVN *phase, bool can_reshape) {

   const TypeInt *t2 = phase->type( in(2) )->isa_int();

   if( !t2 || !t2->is_con() ) return NULL; // Right input is a constant

   const int con = t2->get_con() & ( BitsPerLong - 1 ); // Shift count is always masked

   if ( con == 0 ) return NULL;  // let Identity() handle a 0 shift count

                               // note: mask computation below does not work for 0 shift count

   // We'll be wanting the right-shift amount as a mask of that many bits

   const jlong mask = (((jlong)CONST64(1) << (jlong)(BitsPerJavaInteger*2 - con)) -1);

   // Check for ((x << z) + Y) >>> z.  Replace with x + con>>>z

   // The idiom for rounding to a power of 2 is "(Q+(2^z-1)) >>> z".

   // If Q is "X << z" the rounding is useless.  Look for patterns like

   // ((X<<Z) + Y) >>> Z  and replace with (X + Y>>>Z) & Z-mask.

   Node *add = in(1);

   if( add->Opcode() == Op_AddL ) {

     Node *lshl = add->in(1);

     if( lshl->Opcode() == Op_LShiftL &&

         phase->type(lshl->in(2)) == t2 ) {

       Node *y_z = phase->transform( new (phase->C, 3) URShiftLNode(add->in(2),in(2)) );

       Node *sum = phase->transform( new (phase->C, 3) AddLNode( lshl->in(1), y_z ) );

       return new (phase->C, 3) AndLNode( sum, phase->longcon(mask) );

     }

   }

   // Check for (x & mask) >>> z.  Replace with (x >>> z) & (mask >>> z)

   // This shortens the mask.  Also, if we are extracting a high byte and

   // storing it to a buffer, the mask will be removed completely.

   Node *andi = in(1);

   if( andi->Opcode() == Op_AndL ) {

     const TypeLong *t3 = phase->type( andi->in(2) )->isa_long();

     if( t3 && t3->is_con() ) { // Right input is a constant

       jlong mask2 = t3->get_con();

       mask2 >>= con;  // *signed* shift downward (high-order zeroes do not help)

       Node *newshr = phase->transform( new (phase->C, 3) URShiftLNode(andi->in(1), in(2)) );

       return new (phase->C, 3) AndLNode(newshr, phase->longcon(mask2));

     }

   }

   // Check for "(X << z ) >>> z" which simply zero-extends

   Node *shl = in(1);

   if( shl->Opcode() == Op_LShiftL &&

       phase->type(shl->in(2)) == t2 )

     return new (phase->C, 3) AndLNode( shl->in(1), phase->longcon(mask) );

   return NULL;

 }

 //------------------------------Value------------------------------------------

 // A URShiftINode shifts its input2 right by input1 amount.

 const Type *URShiftLNode::Value( PhaseTransform *phase ) const {

   // (This is a near clone of RShiftLNode::Value.)

   const Type *t1 = phase->type( in(1) );

   const Type *t2 = phase->type( in(2) );

   // Either input is TOP ==> the result is TOP

   if( t1 == Type::TOP ) return Type::TOP;

   if( t2 == Type::TOP ) return Type::TOP;

   // Left input is ZERO ==> the result is ZERO.

   if( t1 == TypeLong::ZERO ) return TypeLong::ZERO;

   // Shift by zero does nothing

   if( t2 == TypeInt::ZERO ) return t1;

   // Either input is BOTTOM ==> the result is BOTTOM

   if (t1 == Type::BOTTOM || t2 == Type::BOTTOM)

     return TypeLong::LONG;

   if (t2 == TypeInt::INT)

     return TypeLong::LONG;

   const TypeLong *r1 = t1->is_long(); // Handy access

   const TypeInt  *r2 = t2->is_int (); // Handy access

   if (r2->is_con()) {

     uint shift = r2->get_con();

     shift &= (2*BitsPerJavaInteger)-1;  // semantics of Java shifts

     // Shift by a multiple of 64 does nothing:

     if (shift == 0)  return t1;

     // Calculate reasonably aggressive bounds for the result.

     jlong lo = (julong)r1->_lo >> (juint)shift;

     jlong hi = (julong)r1->_hi >> (juint)shift;

     if (r1->_hi >= 0 && r1->_lo < 0) {

       // If the type has both negative and positive values,

       // there are two separate sub-domains to worry about:

       // The positive half and the negative half.

       jlong neg_lo = lo;

       jlong neg_hi = (julong)-1 >> (juint)shift;

       jlong pos_lo = (julong) 0 >> (juint)shift;

       jlong pos_hi = hi;

       //lo = MIN2(neg_lo, pos_lo);  // == 0

       lo = neg_lo < pos_lo ? neg_lo : pos_lo;

       //hi = MAX2(neg_hi, pos_hi);  // == -1 >>> shift;

       hi = neg_hi > pos_hi ? neg_hi : pos_hi;

     }

     assert(lo <= hi, "must have valid bounds");

     const TypeLong* tl = TypeLong::make(lo, hi, MAX2(r1->_widen,r2->_widen));

     #ifdef ASSERT

     // Make sure we get the sign-capture idiom correct.

     if (shift == (2*BitsPerJavaInteger)-1) {

       if (r1->_lo >= 0) assert(tl == TypeLong::ZERO, ">>>63 of + is 0");

       if (r1->_hi < 0)  assert(tl == TypeLong::ONE,  ">>>63 of - is +1");

     }

     #endif

     return tl;

   }

   return TypeLong::LONG;                // Give up

 }