On 11/13/2014 06:12 PM, Bastian Koppelmann wrote: > + tcg_gen_ext_i32_i64(t3, r3); > + tcg_gen_concat_i32_i64(t2, r2_low, r2_high); > + /* extend the sign for r2 to high 64 bits */ > + tcg_gen_sari_i64(t4, t2, 63); > + tcg_gen_ext_i32_i64(t1, r1); > + > + tcg_gen_muls2_i64(t1, t3, t1, t3); > + tcg_gen_add2_i64(t1, t3, t2, t4, t1, t3); > +
I don't believe that you need 128 bit arithemetic for multiply-accumulate, either here or elsewhere (e.g. msub). Looking at unsigned, the maximum result of the multiply is 2*(2^n-1), or 2^(2n) - 2^(n+1). Which means that the accumulate with a 2^n-1 value cannot overflow a double-word intermediate result. r~
