countLeadingZeros64
shiftCount = countLeadingZeros64( aSig ) - 11;
shiftCount = countLeadingZeros64( zSig ) - 1;
shiftCount = countLeadingZeros64( aSig );
shiftCount = countLeadingZeros64( zSig0 );
shiftCount = countLeadingZeros64(zSig) - 1;
shiftCount = countLeadingZeros64(aSig) - 11;
static int8 countLeadingZeros64(bits64 a);