c - Redistribute bits from byte array to set bits -

i wish move bits 0,8,16,24 of 32-bit value bits 0,1,2,3 respectively. other bits in input , output zero.

obviously can this:

c = c>>21 + c>>14 + c>>7 + c; c &= 0xf;

but there faster (fewer instructions) way?

c = (((c&bits_0_8_16_24) * bits_0_7_14_21) >> 21) & 0xf;

or wait intel haswell processor, doing in 1 instruction (pext).

update

taking business relationship clarified constraints , assuming 32-bit unsigned values, code may simplified this:

c = (c * bits_7_14_21_28) >> 28;

c bit-manipulation

Kamlesh