λ x : word64 * word64 * word64 * word64,
Interp-η
(λ var : Syntax.base_type → Type,
 λ '(x5, x6, x4, x2)%core,
 uint128_t x7 = ((((uint128_t)x2 * x5) + (((uint128_t)x4 * x6) + (((uint128_t)x6 * x4) + ((uint128_t)x5 * x2)))) + (0x10000 * ((uint128_t)x5 * x5)));
 uint128_t x8 = ((((uint128_t)x2 * x6) + (((uint128_t)x4 * x4) + ((uint128_t)x6 * x2))) + (((uint128_t)x5 * x5) + (0x10000 * (((uint128_t)x6 * x5) + ((uint128_t)x5 * x6)))));
 uint128_t x9 = ((((uint128_t)x2 * x4) + ((uint128_t)x4 * x2)) + ((((uint128_t)x6 * x5) + ((uint128_t)x5 * x6)) + (0x10000 * (((uint128_t)x4 * x5) + (((uint128_t)x6 * x6) + ((uint128_t)x5 * x4))))));
 uint128_t x10 = (((uint128_t)x2 * x2) + (((uint128_t)x4 * x5) + (((uint128_t)x6 * x6) + ((uint128_t)x5 * x4))));
 uint64_t x11 = (uint64_t) (x10 >> 0x30);
 uint64_t x12 = ((uint64_t)x10 & 0xffffffffffff);
 uint128_t x13 = (x7 >> 0x30);
 uint64_t x14 = ((uint64_t)x7 & 0xffffffffffff);
 uint128_t x15 = ((0x1000000000000 * x13) + x14);
 uint128_t x16 = (x15 >> 0x30);
 uint64_t x17 = ((uint64_t)x15 & 0xffffffffffff);
 uint128_t x18 = ((x11 + x9) + (0x10000 * x16));
 uint128_t x19 = (x18 >> 0x30);
 uint64_t x20 = ((uint64_t)x18 & 0xffffffffffff);
 uint128_t x21 = (x12 + x16);
 uint64_t x22 = (uint64_t) (x21 >> 0x30);
 uint64_t x23 = ((uint64_t)x21 & 0xffffffffffff);
 uint128_t x24 = (x19 + x8);
 uint128_t x25 = (x24 >> 0x30);
 uint64_t x26 = ((uint64_t)x24 & 0xffffffffffff);
 uint128_t x27 = (x25 + x17);
 uint64_t x28 = (uint64_t) (x27 >> 0x30);
 uint64_t x29 = ((uint64_t)x27 & 0xffffffffffff);
 uint128_t x30 = (((uint128_t)0x1000000000000 * x28) + x29);
 uint64_t x31 = (uint64_t) (x30 >> 0x30);
 uint64_t x32 = ((uint64_t)x30 & 0xffffffffffff);
 uint64_t x33 = ((x22 + x20) + (0x10000 * x31));
 uint64_t x34 = (x33 >> 0x30);
 uint64_t x35 = (x33 & 0xffffffffffff);
 uint64_t x36 = (x23 + x31);
 uint64_t x37 = (x36 >> 0x30);
 uint64_t x38 = (x36 & 0xffffffffffff);
 return (Return x32, (x34 + x26), (x37 + x35), Return x38))
x
     : word64 * word64 * word64 * word64 → ReturnType (uint64_t * uint64_t * uint64_t * uint64_t)