微软大神“玩”出新花样，求平均值代码还能这样写？

unsigned?average(unsigned?a,?unsigned?b)
{
????return?(a?+?b)?/?2;
}

return?(a?+?b)?/?2

unsigned?average(unsigned?low,?unsigned?high){
????return?low?+?(high?-?low)?/?2;
}

unsigned?average(unsigned?a,?unsigned?b){
????return?(a?/?2)?+?(b?/?2)?+?(a?&?b?&?1);
}

unsigned?average(unsigned?a,?unsigned?b){
????return?(a?&?b)?+?(a?^?b)?/?2;//?变体?(a?^?b)?+?(a?&?b)?*?2
}

unsigned?average(unsigned?a,?unsigned?b)
{
????//?Suppose?"unsigned"?is?a?32-bit?type?and
????//?"unsigned?long?long"?is?a?64-bit?type.
????return?((unsigned?long?long)a?+?b)?/?2;
}

//?x86-64:?Assume?ecx?=?a,?edx?=?b,?upper?32?bits?unknown
????mov?????eax,?ecx????????;?rax?=?ecx?zero-extended?to?64-bit?value
????mov?????edx,?edx????????;?rdx?=?edx?zero-extended?to?64-bit?value
????add?????rax,?rdx????????;?64-bit?addition:?rax?=?rax?+?rdx
????shr?????rax,?1??????????;?64-bit?shift:????rax?=?rax?>>?1
????????????????????????????;??????????????????result?is?zero-extended
????????????????????????????;?Answer?in?eax

//?AArch64?(ARM?64-bit):?Assume?w0?=?a,?w1?=?b,?upper?32?bits?unknown
????uxtw????x0,?w0??????????;?x0?=?w0?zero-extended?to?64-bit?value
????uxtw????x1,?w1??????????;?x1?=?w1?zero-extended?to?64-bit?value
????add?????x0,?x1??????????;?64-bit?addition:?x0?=?x0?+?x1
????ubfx????x0,?x0,?1,?32???;?Extract?bits?1?through?32?from?result
????????????????????????????;?(shift?+?zero-extend?in?one?instruction)
????????????????????????????;?Answer?in?x0

//?Alpha?AXP:?Assume?a0?=?a,?a1?=?b,?both?in?canonical?form
????insll???a0,?#0,?a0??????;?a0?=?a0?zero-extended?to?64-bit?value
????insll???a1,?#0,?a1??????;?a1?=?a1?zero-extended?to?64-bit?value
????addq????a0,?a1,?v0??????;?64-bit?addition:?v0?=?a0?+?a1
????srl?????v0,?#1,?v0??????;?64-bit?shift:????v0?=?v0?>>?1
????addl????zero,?v0,?v0????;?Force?canonical?form
????????????????????????????;?Answer?in?v0

//?MIPS64:?Assume?a0?=?a,?a1?=?b,?sign-extended
????dext????a0,?a0,?0,?32???;?Zero-extend?a0?to?64-bit?value
????dext????a1,?a1,?0,?32???;?Zero-extend?a1?to?64-bit?value
????daddu???v0,?a0,?a1??????;?64-bit?addition:?v0?=?a0?+?a1
????dsrl????v0,?v0,?#1??????;?64-bit?shift:????v0?=?v0?>>?1
????sll?????v0,?#0,?v0??????;?Sign-extend?result
????????????????????????????;?Answer?in?v0

//?Power64:?Assume?r3?=?a,?r4?=?b,?zero-extended
????add?????r3,?r3,?r4??????;?64-bit?addition:?r3?=?r3?+?r4
????rldicl??r3,?r3,?63,?32??;?Extract?bits?63?through?32?from?result
????????????????????????????;?(shift?+?zero-extend?in?one?instruction)
????????????????????????????;?result?in?r3

//?x86-32
????mov?????eax,?a
????add?????eax,?b??????????;?Add,?overflow?goes?into?carry?bit
????rcr?????eax,?1??????????;?Rotate?right?one?place?through?carry

//?x86-64
????mov?????rax,?a
????add?????rax,?b??????????;?Add,?overflow?goes?into?carry?bit
????rcr?????rax,?1??????????;?Rotate?right?one?place?through?carry

//?32-bit?ARM?(A32)
????mov?????r0,?a
????adds????r0,?b???????????;?Add,?overflow?goes?into?carry?bit
????rrx?????r0??????????????;?Rotate?right?one?place?through?carry

//?SH-3
????clrt????????????????????;?Clear?T?flag
????mov?????a,?r0
????addc????b,?r0???????????;?r0?=?r0?+?b?+?T,?overflow?goes?into?T?bit
????rotcr???r0??????????????;?Rotate?right?one?place?through?carry

unsigned?average(unsigned?a,?unsigned?b)
{
#if?defined(_MSC_VER)
????unsigned?sum;
????auto?carry?=?_addcarry_u32(0,?a,?b,?&sum);
????return?_rotr1_carry(sum,?carry);?//?missing?intrinsic!
#elif?defined(__clang__)
????unsigned?carry;
????auto?sum?=?_builtin_adc(a,?b,?0,?&carry);
????return?_builtin_rotateright1throughcarry(sum,?carry);?//?missing?intrinsic!
#elif?defined(__GNUC__)
????unsigned?sum;
????auto?carry?=?__builtin_add_overflow(a,?b,?&sum);
????return?_builtin_rotateright1throughcarry(sum,?carry);?//?missing?intrinsic!
#else
#error?Unsupported?compiler.
#endif
}

//?__clang__?with?ARM-Thumb2
????movs????r2,?#0??????????;?Prepare?to?receive?carry????
????adds????r0,?r0,?r1??????;?Calculate?sum?with?flags????
????adcs????r2,?r2??????????;?r2?holds?carry????
????lsrs????r0,?r0,?#1??????;?Shift?sum?right?one?position????
????lsls????r1,?r2,?#31?????;?Move?carry?to?bit?31????
????adds????r0,?r1,?r0??????;?Combine

float?Q_rsqrt(?float?number?)
{
floatint_t?t;
float?x2,?y;
const?float?threehalfs?=?1.5F;

x2?=?number?*?0.5F;
t.f??=?number;
t.i??=?0x5f3759df?-?(?t.i?>>?1?);???????????????//?what?the?fuck?
y??=?t.f;
y??=?y?*?(?threehalfs?-?(?x2?*?y?*?y?)?);???//?1st?iteration
//y??=?y?*?(?threehalfs?-?(?x2?*?y?*?y?)?);???//?2nd?iteration,?this?can?be?removed

return?y;
}