Request for reviews (L): 6823354: Add intrinsics for{Integer,Long}.{numberOfLeadingZeros,numberOfTrailingZeros}()

[Vladimir Kozlov]

Christian Thalinger wrote:
>> x86_32.ad - Why you did not remove TEMP dst? Do you need it?
>>
>> +   effect(TEMP dst
> 
> I think I kept it because I'm not sure if one register of a long
> register pair can be the same as the dst register.  Can it?

Yes, you are right, it is needed.

> 
>> connode.cpp - new Ideal methods should be Value methods since
>> it is the value transformation and it misses checks for Top:
>>
>> const Type* CountLeadingZerosINode::Value( PhaseTransform *phase ) const {
>>     const Type *t = phase->type( in(1) );
>>     if( t == Type::TOP ) return Type::TOP;
>>     const TypeInt *ti = t->isa_int();
>>     if (ti && ti->is_con()) {
> 
> I see.  I'm currently trying to change that but I have some problems.
> Could you explain a little how Value() is supposed to work?

What problems do you have?
Look on, for example, ConvL2INode::Value(). And your code:

const Type* CountLeadingZerosINode::Value( PhaseTransform *phase ) const {
   const Type *t = phase->type( in(1) );
   if( t == Type::TOP ) return Type::TOP;
   const TypeInt *ti = t->isa_int();
   if (ti && ti->is_con()) {
     jint i = ti->get_con();
     // HD, Figure 5-6
     if (i == 0)
       return TypeInt::make(BitsPerInt);
     jint n = 1;
     unsigned int x = i;
     if (x >> 16 == 0) { n += 16; x <<= 16; }
     if (x >> 24 == 0) { n +=  8; x <<=  8; }
     if (x >> 28 == 0) { n +=  4; x <<=  4; }
     if (x >> 30 == 0) { n +=  2; x <<=  2; }
     n -= x >> 31;
     return TypeInt::make(n);
   }
   return bottom_type();
}


Vladimir