ICS datalab总结

/*  * bitAnd - x&y using only ~ and |  *   Example: bitAnd(6, 5) = 4 *   Legal ops: ~ | *   Max ops: 8 *   Rating: 1 */int bitAnd(int x, int y) {return ~(~x|~y);}/*  * getByte - Extract byte n from word x *   Bytes numbered from 0 (LSB) to 3 (MSB) *   Examples: getByte(0x12345678,1) = 0x56 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 6 *   Rating: 2 */int getByte(int x, int n) {int t=0xff;return t&(x>>(n<<3));}/*  * logicalShift - shift x to the right by n, using a logical shift *   Can assume that 0 <= n <= 31 *   Examples: logicalShift(0x87654321,4) = 0x08765432 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 20 *   Rating: 3  */int logicalShift(int x, int n) {int t=(1<<31)&x;return (x>>n)^((t>>n)<<1);}/* * bitCount - returns count of number of 1's in word *   Examples: bitCount(5) = 2, bitCount(7) = 3 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 40 *   Rating: 4 */int bitCount(int x) {int sum=0;int Mask=1|(1<<8);    Mask=Mask|(Mask<<16);sum=x&Mask;sum+=(x>>1)&Mask;sum+=(x>>2)&Mask;sum+=(x>>3)&Mask;sum+=(x>>4)&Mask;sum+=(x>>5)&Mask;sum+=(x>>6)&Mask;sum+=(x>>7)&Mask;sum+=(sum>>16);sum+=(sum>>8);return sum&0xff;}/*  * bang - Compute !x without using ! *   Examples: bang(3) = 0, bang(0) = 1 *   Legal ops: ~ & ^ | + << >> *   Max ops: 12 *   Rating: 4  */int bang(int x) {return ((~(x|(~x+1)))>>31)&1;}/*  * tmin - return minimum two's complement integer  *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 4 *   Rating: 1 */int tmin(void) {return (1<<31);}/*  * fitsBits - return 1 if x can be represented as an  *  n-bit, two's complement integer. *   1 <= n <= 32 *   Examples: fitsBits(5,3) = 0, fitsBits(-4,3) = 1 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 15 *   Rating: 2 */int fitsBits(int x, int n) {int t=33+(~n);    return !(x^((x<<t)>>t));}/*  * divpwr2 - Compute x/(2^n), for 0 <= n <= 30 *  Round toward zero *   Examples: divpwr2(15,1) = 7, divpwr2(-33,4) = -2 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 15 *   Rating: 2 */int divpwr2(int x, int n) {int bias=(x>>31)&((1<<n)+(~0));return (x+bias)>>n;}/*  * negate - return -x  *   Example: negate(1) = -1. *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 5 *   Rating: 2 */int negate(int x) {  return (~x+1);}/*  * isPositive - return 1 if x > 0, return 0 otherwise  *   Example: isPositive(-1) = 0. *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 8 *   Rating: 3 */int isPositive(int x) {  return !((x>>31)|(!x));}/*  * isLessOrEqual - if x <= y  then return 1, else return 0  *   Example: isLessOrEqual(4,5) = 1. *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 24 *   Rating: 3 */int isLessOrEqual(int x, int y) {int signx=x>>31;  int signy=y>>31;  int signSame=((x+(~y))>>31)&(!(signx^signy));  int signDiffer=signx&(!signy);  return signDiffer|signSame;  }/* * ilog2 - return floor(log base 2 of x), where x > 0 *   Example: ilog2(16) = 4 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 90 *   Rating: 4 */int ilog2(int x) {int sum1,sum2,sum3,sum4,sum5;sum1=(!!(x>>16))<<4;x=x>>sum1;sum2=(!!(x>>8))<<3;x=x>>sum2;sum3=(!!(x>>4))<<2;x=x>>sum3;sum4=(!!(x>>2))<<1;x=x>>sum4;sum5=(!!(x>>1));return sum1+sum2+sum3+sum4+sum5;}/*  * float_neg - Return bit-level equivalent of expression -f for *   floating point argument f. *   Both the argument and result are passed as unsigned int's, but *   they are to be interpreted as the bit-level representations of *   single-precision floating point values. *   When argument is NaN, return argument. *   Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while *   Max ops: 10 *   Rating: 2 */unsigned float_neg(unsigned uf) {unsigned result=uf^0x80000000;if((uf&0x7fffffff)>0x7f800000)result=uf;return result;}/*  * float_i2f - Return bit-level equivalent of expression (float) x *   Result is returned as unsigned int, but *   it is to be interpreted as the bit-level representation of a *   single-precision floating point values. *   Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while *   Max ops: 30 *   Rating: 4 */unsigned float_i2f(int x) {unsigned sign=0,shiftleft=1,flag=0;  unsigned absx=x;  if( x==0 ) return 0;  if( x<0 ){  sign=0x80000000;  absx=(~x+1);  }  while((absx&0x80000000)==0){absx<<=1;  shiftleft++;  }  absx<<=1;if( (absx & 0x01ff) > 0x0100 ) flag=1;if( (absx & 0x03ff) == 0x0300 ) flag=1;return sign+(absx>>9)+((159-shiftleft)<<23)+flag;  }/*  * float_twice - Return bit-level equivalent of expression 2*f for *   floating point argument f. *   Both the argument and result are passed as unsigned int's, but *   they are to be interpreted as the bit-level representation of *   single-precision floating point values. *   When argument is NaN, return argument *   Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while *   Max ops: 30 *   Rating: 4 */unsigned float_twice(unsigned uf) {unsigned e = uf & 0x7F800000;        unsigned sign = uf & 0x80000000;        if (e) {           if (  e != 0x7F800000 ) {            uf = uf + 0x00800000;              }      }      else         uf = ( uf << 1) | sign ;     return uf;  }