Move `BitPosition` into its own file.

This will allow the GC info encoder and the JIT to use this
function without pulling in the entire utilcode header.

1 files changed, 1 insertions, 47 deletions

diff --git a/src/inc/utilcode.h b/src/inc/utilcode.h
index b9985a8b25..bb7c8bad81 100644
--- a/src/inc/utilcode.h
+++ b/src/inc/utilcode.h
@@ -1041,53 +1041,7 @@ inline int CountBits(int iNum)
     return (iBits);
 }
 
-//------------------------------------------------------------------------
-// BitPosition: Return the position of the single bit that is set in 'value'.
-//
-// Return Value:
-//    The position (0 is LSB) of bit that is set in 'value'
-//
-// Notes:
-//    'value' must have exactly one bit set.
-//    The algorithm is as follows:
-//    - PRIME is a prime bigger than sizeof(unsigned int), which is not of the
-//      form 2^n-1.
-//    - Taking the modulo of 'value' with this will produce a unique hash for all
-//      powers of 2 (which is what "value" is).
-//    - Entries in hashTable[] which are -1 should never be used. There
-//      should be PRIME-8*sizeof(value) entries which are -1 .
-//
-inline
-unsigned            BitPosition(unsigned value)
-{
-    _ASSERTE((value != 0) && ((value & (value-1)) == 0));
-#ifndef _TARGET_AMD64_
-    const unsigned PRIME = 37;
-
-    static const char hashTable[PRIME] =
-    {
-        -1,  0,  1, 26,  2, 23, 27, -1,  3, 16,
-        24, 30, 28, 11, -1, 13,  4,  7, 17, -1,
-        25, 22, 31, 15, 29, 10, 12,  6, -1, 21,
-        14,  9,  5, 20,  8, 19, 18
-    };
-
-    _ASSERTE(PRIME >= 8*sizeof(value));
-    _ASSERTE(sizeof(hashTable) == PRIME);
-
-
-    unsigned hash   = value % PRIME;
-    unsigned index  = hashTable[hash];
-    _ASSERTE(index != (unsigned char)-1);
-#else
-    // not enabled for x86 because BSF is extremely slow on Atom
-    // (15 clock cycles vs 1-3 on any other Intel CPU post-P4)
-    DWORD index;
-    BitScanForward(&index, value);
-#endif
-    return index;
-}
-
+#include "bitposition.h"
 
 // Used to remove trailing zeros from Decimal types.
 // NOTE: Assumes hi32 bits are empty (used for conversions from Cy->Dec)