On Tue, Mar 27, 2018 at 5:35 PM, Richard Henderson <
richard.hender...@linaro.org> wrote:
> On 03/28/2018 01:43 AM, Michael Clark wrote:
> > > + if ((ct & TCG_CT_CONST_N12) && val >= -2047 && val <= 2047) {
> >
> > +2048?
>
Yes of course, you're right. It's safe. I just hadn't thought about it
carefully enough.
> > We use this constraint for a negatable immediate and the constraint is
> only
> > applied to sub. We have no subi, so we implement subi as addi rd, rs1,
> -imm
> >
> > case INDEX_op_sub_i32:
> > if (c2) {
> > tcg_out_opc_imm(s, is32bit ? OPC_ADDI : OPC_ADDIW, a0, a1,
> -a2);
> > } else {
> > tcg_out_opc_reg(s, is32bit ? OPC_SUB : OPC_SUBW, a0, a1, a2);
> > }
> > break;
>
> That's my point. The "positive" range for addition is -2048...2047, so the
> "negative" range for subtraction should be -2047...2048.
>
Got it. Thanks.
