Commit a2d12f0f authored by Peter Maydell's avatar Peter Maydell
Browse files

target/arm: Add some comments in Thumb decode 



Add some comments to the Thumb decoder indicating what bits
of the instruction have been decoded at various points in
the code.

This is not an exhaustive set of comments; we're gradually
adding comments as we work with particular bits of the code.

Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: default avatarRichard Henderson <richard.henderson@linaro.org>
Message-id: 20181002163556.10279-6-peter.maydell@linaro.org
parent 55203189

target/arm/translate.c

+17 −3
Original line number Diff line number Diff line
@@ -10623,6 +10623,10 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn) 
            tmp2 = load_reg(s, rm);

            if ((insn & 0x70) != 0)

                goto illegal_op;

            /*

             * 0b1111_1010_0xxx_xxxx_1111_xxxx_0000_xxxx:

             *  - MOV, MOVS (register-shifted register), flagsetting

             */

            op = (insn >> 21) & 3;

            logic_cc = (insn & (1 << 20)) != 0;

            gen_arm_shift_reg(tmp, op, tmp2, logic_cc);
@@ -11674,7 +11678,11 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn) 
        rd = insn & 7;

        op = (insn >> 11) & 3;

        if (op == 3) {

            /* add/subtract */

            /*

             * 0b0001_1xxx_xxxx_xxxx

             *  - Add, subtract (three low registers)

             *  - Add, subtract (two low registers and immediate)

             */

            rn = (insn >> 3) & 7;

            tmp = load_reg(s, rn);

            if (insn & (1 << 10)) {
@@ -11711,7 +11719,10 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn) 
        }

        break;

    case 2: case 3:

        /* arithmetic large immediate */

        /*

         * 0b001x_xxxx_xxxx_xxxx

         *  - Add, subtract, compare, move (one low register and immediate)

         */

        op = (insn >> 11) & 3;

        rd = (insn >> 8) & 0x7;

        if (op == 0) { /* mov */
@@ -11848,7 +11859,10 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn) 
            break;

        }



        /* data processing register */

        /*

         * 0b0100_00xx_xxxx_xxxx

         *  - Data-processing (two low registers)

         */

        rd = insn & 7;

        rm = (insn >> 3) & 7;

        op = (insn >> 6) & 0xf;