自作CPUの分岐予測器(Gshare)をちゃんとデバッグしたいため、モデルとの比較環境を構築している。
まずはGHR(Global History Table)の比較をしたいため、RTLとの比較環境を構築した。
もう少し進めて、モデル側にも同様なgshareの予測器を追加して、予測が一致するかを検証するようにした。
if (is_cond_branch_inst(iss_insn.bits())) { const size_t iss_bhr_mask = (1 << iss_bhr_length) - 1; size_t bim_array_index = (iss_pc >> 1) / iss_cache_block_byte_size; size_t bim_block_internal_index = (iss_pc & (iss_cache_block_byte_size -1)) >> 1; bim_array_index = (bim_array_index ^ iss_bhr) & iss_bhr_mask; // fprintf (gshare_log_fp, "bim_array_index = %d, bim_block_internal_index = %d\n", // bim_array_index, // bim_block_internal_index); uint8_t bim_counter = bim_array.at(bim_array_index)->bim[bim_block_internal_index]; bool iss_predict_taken = (bim_counter >> 1) & 1; bool is_branch_taken = iss_next_pc != iss_pc + cond_inst_size(iss_insn.bits()); fprintf (gshare_log_fp, "GSHARE MODEL : PC = %08lx (%02d,%02d), index = (%4x, %2x), MODEL_BHR = %s, predict = %s, result = %s, %s ", iss_pc, rtl_cmt_id, rtl_grp_id, static_cast<unsigned int>(bim_array_index), static_cast<unsigned int>(bim_block_internal_index), to_binString(iss_bhr & ((1 << iss_bhr_length)-1), iss_bhr_length).c_str(), iss_predict_taken ? " TAKEN" : "NOT TAKEN", is_branch_taken ? " TAKEN" : "NOT TAKEN", iss_predict_taken == is_branch_taken ? "MATCH" : "FAIL ");
いろんな情報を比較できるようにした。これで、デバッグがもうちょっとやりやすくなるかな？ モデル側の分岐予測のヒット率を確認すると、マイクロベンチマークであったとしてもかなり高くなっている(90%以上)。 ちゃんとデバッグできるかな？
GSHARE MODEL : PC = 80002578 (48,04), index = ( 3b5, 1c), MODEL_BHR = 1111111111, predict = TAKEN, result = TAKEN, MATCH // BHR RTL = 1111111111 GSHARE MODEL : PC = 80002578 (49,04), index = ( 3b5, 1c), MODEL_BHR = 1111111111, predict = TAKEN, result = TAKEN, MATCH // BHR RTL = 1111111111 GSHARE MODEL : PC = 80002578 (50,04), index = ( 3b5, 1c), MODEL_BHR = 1111111111, predict = TAKEN, result = TAKEN, MATCH // BHR RTL = 1111111111 GSHARE MODEL : PC = 80002578 (51,04), index = ( 3b5, 1c), MODEL_BHR = 1111111111, predict = TAKEN, result = TAKEN, MATCH // BHR RTL = 1111111111 GSHARE MODEL : PC = 80002578 (52,04), index = ( 3b5, 1c), MODEL_BHR = 1111111111, predict = TAKEN, result = NOT TAKEN, FAIL // BHR RTL = 1111111110 GSHARE MODEL : PC = 8000241e (58,01), index = ( 3b6, f), MODEL_BHR = 1111111110, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1111111110, ISS = 1111111100 GSHARE MODEL : PC = 80002002 (01,02), index = ( 3bc, 1), MODEL_BHR = 1111111100, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1111111111, ISS = 1111111001 GSHARE MODEL : PC = 8000200c (07,04), index = ( 3b9, 6), MODEL_BHR = 1111111001, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1111111111, ISS = 1111110011 GSHARE MODEL : PC = 80002014 (11,02), index = ( 3b3, a), MODEL_BHR = 1111110011, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1111111111, ISS = 1111100110 GSHARE MODEL : PC = 80002760 (13,02), index = ( 3a8, 10), MODEL_BHR = 1111100110, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1111111111, ISS = 1111001100 GSHARE MODEL : PC = 8000276c (14,08), index = ( 382, 16), MODEL_BHR = 1111001100, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1111111111, ISS = 1110011001 GSHARE MODEL : PC = 80002002 (19,02), index = ( 3d9, 1), MODEL_BHR = 1110011001, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1111111111, ISS = 1100110011 GSHARE MODEL : PC = 8000200c (20,04), index = ( 373, 6), MODEL_BHR = 1100110011, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1111111110, ISS = 1001100110 GSHARE MODEL : PC = 80002014 (27,01), index = ( 226, a), MODEL_BHR = 1001100110, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1111101111, ISS = 0011001101 GSHARE MODEL : PC = 80002760 (31,02), index = ( 83, 10), MODEL_BHR = 0011001101, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1111011110, ISS = 0110011010 GSHARE MODEL : PC = 8000276c (34,08), index = ( 1d4, 16), MODEL_BHR = 0110011010, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1111011111, ISS = 1100110101 GSHARE MODEL : PC = 80002002 (36,02), index = ( 375, 1), MODEL_BHR = 1100110101, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1110111111, ISS = 1001101011 GSHARE MODEL : PC = 8000200c (37,04), index = ( 22b, 6), MODEL_BHR = 1001101011, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 0111101111, ISS = 0011010111 GSHARE MODEL : PC = 80002014 (40,02), index = ( 97, a), MODEL_BHR = 0011010111, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1111011110, ISS = 0110101110 GSHARE MODEL : PC = 80002760 (44,02), index = ( 1e0, 10), MODEL_BHR = 0110101110, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1110111100, ISS = 1101011100 GSHARE MODEL : PC = 8000276c (47,08), index = ( 312, 16), MODEL_BHR = 1101011100, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1110011111, ISS = 1010111001 GSHARE MODEL : PC = 80002002 (49,02), index = ( 2f9, 1), MODEL_BHR = 1010111001, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1100111111, ISS = 0101110011 GSHARE MODEL : PC = 8000200c (50,04), index = ( 133, 6), MODEL_BHR = 0101110011, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1111001110, ISS = 1011100110 GSHARE MODEL : PC = 80002014 (54,01), index = ( 2a6, a), MODEL_BHR = 1011100110, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1100111011, ISS = 0111001101 GSHARE MODEL : PC = 80002760 (58,02), index = ( 183, 10), MODEL_BHR = 0111001101, predict = TAKEN, result = NOT TAKEN, FAIL // Warning : BHR different: RTL = 1001110110, ISS = 1110011010 GSHARE MODEL : PC = 8000276c (61,08), index = ( 3d4, 16), MODEL_BHR = 1110011010, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 1011011111, ISS = 1100110101 GSHARE MODEL : PC = 80002002 (63,02), index = ( 375, 1), MODEL_BHR = 1100110101, predict = TAKEN, result = TAKEN, MATCH // Warning : BHR different: RTL = 0110111111, ISS = 1001101011
