On 4/23/19 11:58 AM, David Hildenbrand wrote: >> +void tcg_gen_gvec_shls(unsigned vece, uint32_t dofs, uint32_t aofs, >> + TCGv_i32 shift, uint32_t oprsz, uint32_t maxsz); >> +void tcg_gen_gvec_shrs(unsigned vece, uint32_t dofs, uint32_t aofs, >> + TCGv_i32 shift, uint32_t oprsz, uint32_t maxsz); >> +void tcg_gen_gvec_sars(unsigned vece, uint32_t dofs, uint32_t aofs, >> + TCGv_i32 shift, uint32_t oprsz, uint32_t maxsz); > > I assume all irrelevant bits of the shift have to be masked off by the > caller, right?
Correct, just like for integers. > > On s390x, I would use it for (one variant of) VECTOR ELEMENT SHIFT like > this: > > > +static DisasJumpType op_ves(DisasContext *s, DisasOps *o) > +{ > + const uint8_t es = get_field(s->fields, m4); > + const uint8_t d2 = get_field(s->fields, d2) & > + (NUM_VEC_ELEMENT_BITS(es) - 1); > + const uint8_t v1 = get_field(s->fields, v1); > + const uint8_t v3 = get_field(s->fields, v3); > + TCGv_i32 shift; > + > + if (es > ES_64) { > + gen_program_exception(s, PGM_SPECIFICATION); > + return DISAS_NORETURN; > + } > + > + shift = tcg_temp_new_i32(); > + tcg_gen_extrl_i64_i32(shift, o->addr1); > + tcg_gen_andi_i32(shift, shift, NUM_VEC_ELEMENT_BITS(es) - 1); > + > + switch (s->fields->op2) { > + case 0x30: > + if (likely(!get_field(s->fields, b2))) { > + gen_gvec_fn_2i(shli, es, v1, v3, d2); > + } else { > + gen_gvec_fn_2s(shls, es, v1, v3, shift); > + } > + break; > + case 0x3a: > + if (likely(!get_field(s->fields, b2))) { > + gen_gvec_fn_2i(sari, es, v1, v3, d2); > + } else { > + gen_gvec_fn_2s(sars, es, v1, v3, shift); > + } > + break; > + case 0x38: > + if (likely(!get_field(s->fields, b2))) { > + gen_gvec_fn_2i(shri, es, v1, v3, d2); > + } else { > + gen_gvec_fn_2s(shrs, es, v1, v3, shift); > + } > + break; > + default: > + g_assert_not_reached(); > + } > + tcg_temp_free_i32(shift); > + return DISAS_NEXT; > +} Looks plausible. I might have hoisted the b2 == 0 check, and avoid the other tcg arithmetic when unused. > Does it still make sense to special-case the const immediate case? Yes. We cannot turn non-constant scalar shift into immediate shift, when it can be shown that the scalar is constant. x86 (and s390, obviously) has all 3 forms of shift. aarch64 and powerpc are missing the scalar form, having only the immediate and vector forms. The expansion that we do when a form is missing may make it very difficult to undo via constant propagation. r~