2. Write a program that will calculate the log base 2 of an integer using the In

Question

2. Write a program that will calculate the log base 2 of an integer using the Intel BSR instruction. The BSR instruction has the format BSR register, data The instruction finds the position of the leftmost 1 bit in the second operand, which can be a memory location or a register. This result is stored in the first register. #include kiostream> using namespace std; int main (int argn char argv [1) int number log cout Enter a number cin number; asm t Calculate the log2 of number and store the result in log cout The logarithm is log endl; return 0;

Explanation / Answer

#include <iostream>
using namespace std;

int main(int argn, char *argv[]) {
   int number, log;
   cout<<"Enter a number";
   cin>>number;
   _asm {
       CALL #__gnu_cxx::__enable_if<std::__is_integer<int>::__value, double>::__type std::log<int>(int)
MOV R12, R8
MOV R13, R9
MOV R14, R10
MOV R15, R11
MOV #2, R12
CALL #__gnu_cxx::__enable_if<std::__is_integer<int>::__value, double>::__type std::log<int>(int)
MOV R12, R8
MOV R13, R9
MOV R14, R10
MOV R15, R11
       BSR $log R15      
   }
   cout<<"The logarithm is"<<log<<endl;
   return 0;
}

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