Method emit_muldiv

LiveRecomp/live_generator.cpp:1751–1910

}

void N64Recomp::LiveGenerator::emit_muldiv(InstrId instr_id, int reg1, int reg2) const {
    sljit_sw src1;
    sljit_sw src1w;
    sljit_sw src2;
    sljit_sw src2w;
    get_gpr_values(reg1, src1, src1w);
    get_gpr_values(reg2, src2, src2w);
    
    auto do_mul32_op = [src1, src1w, src2, src2w, this](bool is_signed) {
        // Load the two inputs into the multiplication input registers (R0/R1).
        if (is_signed) {
            // 32-bit signed multiplication is really 64 bits * 35 bits, so load accordingly.
            sljit_emit_op1(compiler, SLJIT_MOV, SLJIT_R0, 0, src1, src1w); 

            // Sign extend to 35 bits by shifting left by 64 - 35 and then shifting right by the same amount.
            sljit_emit_op2(compiler, SLJIT_SHL, SLJIT_R1, 0, src2, src2w, SLJIT_IMM, 64 - 35);
            sljit_emit_op2(compiler, SLJIT_ASHR, SLJIT_R1, 0, SLJIT_R1, 0, SLJIT_IMM, 64 - 35);
        }
        else {
            sljit_emit_op1(compiler, SLJIT_MOV_U32, SLJIT_R0, 0, src1, src1w);
            sljit_emit_op1(compiler, SLJIT_MOV_U32, SLJIT_R1, 0, src2, src2w);
        }

        // Perform the multiplication.
        sljit_emit_op0(compiler, is_signed ? SLJIT_LMUL_SW : SLJIT_LMUL_UW);

        // Move the results into hi and lo with sign extension.
        sljit_emit_op2(compiler, SLJIT_ASHR, Registers::hi, 0, SLJIT_R0, 0, SLJIT_IMM, 32);
        sljit_emit_op1(compiler, SLJIT_MOV_S32, Registers::lo, 0, SLJIT_R0, 0);
    };
    
    auto do_mul64_op = [src1, src1w, src2, src2w, this](bool is_signed) {
        // Load the two inputs into the multiplication input registers (R0/R1).
        sljit_emit_op1(compiler, SLJIT_MOV, SLJIT_R0, 0, src1, src1w); 
        sljit_emit_op1(compiler, SLJIT_MOV, SLJIT_R1, 0, src2, src2w);

        // Perform the multiplication.
        sljit_emit_op0(compiler, is_signed ? SLJIT_LMUL_SW : SLJIT_LMUL_UW);

        // Move the results into hi and lo.
        sljit_emit_op1(compiler, SLJIT_MOV, Registers::hi, 0, SLJIT_R1, 0);
        sljit_emit_op1(compiler, SLJIT_MOV, Registers::lo, 0, SLJIT_R0, 0);
    };
    
    auto do_div_op = [src1, src1w, src2, src2w, this](bool doubleword, bool is_signed) {
        // Pick the division opcode based on the bit width and signedness.
        // Note that the 64-bit division opcode is used for 32-bit signed division to match hardware behavior and prevent overflow.
        sljit_sw div_opcode = doubleword ?
            (is_signed ? SLJIT_DIVMOD_SW : SLJIT_DIVMOD_UW) :
            (is_signed ? SLJIT_DIVMOD_SW : SLJIT_DIVMOD_U32);

        // Pick the move opcode to use for loading the operands.
        sljit_sw load_opcode = doubleword ? SLJIT_MOV :
            (is_signed ? SLJIT_MOV_S32 : SLJIT_MOV_U32);

        // Pick the move opcode to use for saving the results.
        sljit_sw save_opcode = doubleword ? SLJIT_MOV : SLJIT_MOV_S32;