17 Dec
2003
17 Dec
'03
11:17 p.m.
Since people are playing "my processor is better than your processor"... This case (counting number of bits set in n-bit word) takes 2n+1 instructions on the HP PA-RISC processor. (HP's compiler generates 2n+2 instructions, GCC takes 2n+1). No branch instructions are generated in either case. HP's compiler uses the conditional skip feature of the PA architecture, while GCC converts if (x&(1<<n)) y++; into the equivalent branchless form: y += ((x>>n)&1); ( (x>>n)&1 being a single-instruction bitfield extract on the PA). - Bill