Merge pull request #891 from kupsch/remove-muldivfuncs

code cleanup integer funcs to * and / by constants

common/src/linuxKludges.C

@@ -106,99 +106,6 @@ int P_copy(const char *from, const char *to) {
 }
 
 
-unsigned long long PDYN_div1000(unsigned long long in) {
-   /* Divides by 1000 without an integer division instruction or library call, both of
-    * which are slow.
-    * We do only shifts, adds, and subtracts.
-    *
-    * We divide by 1000 in this way:
-    * multiply by 1/1000, or multiply by (1/1000)*2^30 and then right-shift by 30.
-    * So what is 1/1000 * 2^30?
-    * It is 1,073,742.   (actually this is rounded)
-    * So we can multiply by 1,073,742 and then right-shift by 30 (neat, eh?)
-    *
-    * Now for multiplying by 1,073,742...
-    * 1,073,742 = (1,048,576 + 16384 + 8192 + 512 + 64 + 8 + 4 + 2)
-    * or, slightly optimized:
-    * = (1,048,576 + 16384 + 8192 + 512 + 64 + 16 - 2)
-    * for a total of 8 shifts and 6 add/subs, or 14 operations.
-    *
-    */
-
-   unsigned long long temp = in << 20; // multiply by 1,048,576
-      // beware of overflow; left shift by 20 is quite a lot.
-      // If you know that the input fits in 32 bits (4 billion) then
-      // no problem.  But if it's much bigger then start worrying...
-
-   temp += in << 14; // 16384
-   temp += in << 13; // 8192
-   temp += in << 9;  // 512
-   temp += in << 6;  // 64
-   temp += in << 4;  // 16
-   temp -= in >> 2;  // 2
-
-   return (temp >> 30); // divide by 2^30
-}
-
-unsigned long long PDYN_divMillion(unsigned long long in) {
-   /* Divides by 1,000,000 without an integer division instruction or library call,
-    * both of which are slow.
-    * We do only shifts, adds, and subtracts.
-    *
-    * We divide by 1,000,000 in this way:
-    * multiply by 1/1,000,000, or multiply by (1/1,000,000)*2^30 and then right-shift
-    * by 30.  So what is 1/1,000,000 * 2^30?
-    * It is 1,074.   (actually this is rounded)
-    * So we can multiply by 1,074 and then right-shift by 30 (neat, eh?)
-    *
-    * Now for multiplying by 1,074
-    * 1,074 = (1024 + 32 + 16 + 2)
-    * for a total of 4 shifts and 4 add/subs, or 8 operations.
-    *
-    * Note: compare with div1000 -- it's cheaper to divide by a million than
-    *       by a thousand (!)
-    *
-    */
-
-   unsigned long long temp = in << 10; // multiply by 1024
-      // beware of overflow...if the input arg uses more than 52 bits
-      // than start worrying about whether (in << 10) plus the smaller additions
-      // we're gonna do next will fit in 64...
-
-   temp += in << 5; // 32
-   temp += in << 4; // 16
-   temp += in << 1; // 2
-
-   return (temp >> 30); // divide by 2^30
-}
-
-unsigned long long PDYN_mulMillion(unsigned long long in) {
-   unsigned long long result = in;
-
-   /* multiply by 125 by multiplying by 128 and subtracting 3x */
-   result = (result << 7) - result - result - result;
-
-   /* multiply by 125 again, for a total of 15625x */
-   result = (result << 7) - result - result - result;
-
-   /* multiply by 64, for a total of 1,000,000x */
-   result <<= 6;
-
-   /* cost was: 3 shifts and 6 subtracts
-    * cost of calling mul1000(mul1000()) would be: 6 shifts and 4 subtracts
-    *
-    * Another algorithm is to multiply by 2^6 and then 5^6.
-    * The former is super-cheap (one shift); the latter is more expensive.
-    * 5^6 = 15625 = 16384 - 512 - 256 + 8 + 1
-    * so multiplying by 5^6 means 4 shift operations and 4 add/sub ops
-    * so multiplying by 1000000 means 5 shift operations and 4 add/sub ops.
-    * That may or may not be cheaper than what we're doing (3 shifts; 6 subtracts);
-    * I'm not sure.  --ari
-    */
-
-   return result;
-}
-
 #include <cxxabi.h>
 #include <boost/thread/mutex.hpp>
 #include <boost/thread/lock_guard.hpp>

common/src/linuxKludges.h

@@ -34,10 +34,6 @@
 
 #include <vector>
 
-unsigned long long PDYN_div1000(unsigned long long in);
-unsigned long long PDYN_divMillion(unsigned long long in);
-unsigned long long PDYN_mulMillion(unsigned long long in);
-
 COMMON_EXPORT bool PtraceBulkRead(Dyninst::Address inTraced, unsigned size, void *inSelf, int pid);
 
 COMMON_EXPORT bool PtraceBulkWrite(Dyninst::Address inTraced, unsigned size, const void *inSelf, int pid);