[{"id":3688669,"web_url":"http://patchwork.ozlabs.org/comment/3688669/","msgid":"","list_archive_url":null,"date":"2026-05-08T18:24:33","subject":"Re: [PATCH v3 15/32] target/mips: add Octeon MTM0 instruction","submitter":{"id":72104,"url":"http://patchwork.ozlabs.org/api/people/72104/","name":"Richard Henderson","email":"richard.henderson@linaro.org"},"content":"On 5/8/26 10:12, James Hilliard wrote:\n> MTM0 loads the low multiplier operand pair from rs/rt, starts a new\n> multiplier chain, clears the upper multiplier limbs, and resets partial\n> products.\n> \n> Add the decode and translator path that writes MPL[0] and MPL[3].\n> \n> Signed-off-by: James Hilliard \n> ---\n> Changes v2 -> v3:\n> - Split MTM0 out of the combined Octeon arithmetic and memory\n> instruction patch. (requested by Richard Henderson)\n> ---\n> target/mips/tcg/octeon.decode | 2 ++\n> target/mips/tcg/octeon_translate.c | 55 ++++++++++++++++++++++++++++++++++++++\n> 2 files changed, 57 insertions(+)\n> \n> diff --git a/target/mips/tcg/octeon.decode b/target/mips/tcg/octeon.decode\n> index 56c54e0973..2dadb13845 100644\n> --- a/target/mips/tcg/octeon.decode\n> +++ b/target/mips/tcg/octeon.decode\n> @@ -43,6 +43,8 @@ SEQ 011100 ..... ..... ..... 00000 101010 @r3\n> SNE 011100 ..... ..... ..... 00000 101011 @r3\n> SEQI 011100 rs:5 rt:5 imm:s10 101110 &cmpi\n> SNEI 011100 rs:5 rt:5 imm:s10 101111 &cmpi\n> +&r2 rs rt\n> +MTM0 011100 rs:5 rt:5 00000 00000 001000 &r2\n> \n> &saa base rt\n> @saa ...... base:5 rt:5 ................ &saa\n> diff --git a/target/mips/tcg/octeon_translate.c b/target/mips/tcg/octeon_translate.c\n> index f94f765055..186200036e 100644\n> --- a/target/mips/tcg/octeon_translate.c\n> +++ b/target/mips/tcg/octeon_translate.c\n> @@ -216,6 +216,60 @@ static bool trans_ZCBT(DisasContext *ctx, arg_zcb *a)\n> return trans_ZCB(ctx, a);\n> }\n> \n> +static ptrdiff_t octeon_tc_mpl_offset(unsigned int index)\n> +{\n> + return offsetof(CPUMIPSState, active_tc.octeon.MPL[index]);\n> +}\n> +\n> +static ptrdiff_t octeon_tc_p_offset(unsigned int index)\n> +{\n> + return offsetof(CPUMIPSState, active_tc.octeon.P[index]);\n> +}\n> +\n> +static void octeon_store_tc_field(ptrdiff_t offset, TCGv_i64 value)\n> +{\n> + tcg_gen_st_i64(value, tcg_env, offset);\n> +}\n\nAre these really helpful?\n\n> +static void octeon_zero_partial_product_state(void)\n> +{\n> + TCGv_i64 zero = tcg_constant_i64(0);\n> +\n> + for (int i = 0; i < 2 * 3; i++) {\n> + octeon_store_tc_field(octeon_tc_p_offset(i), zero);\n> + }\n> +}\n\nYou probably want to use ARRAY_SIZE instead of \"2 * 3\".\n\n> +static bool trans_mtm(DisasContext *ctx, arg_r2 *a, unsigned int index)\n> +{\n> + TCGv_i64 value = tcg_temp_new_i64();\n> +\n> + gen_load_gpr(value, a->rs);\n> + octeon_store_tc_field(octeon_tc_mpl_offset(index), value);\n> + gen_load_gpr(value, a->rt);\n> + octeon_store_tc_field(octeon_tc_mpl_offset(index + 3), value);\n> + if (index == 0) {\n> + octeon_clear_upper_multiplier_state();\n> + }\n\nThis does not correspond to my documentation.\n\n MPL0<63:0> = GPR[rs]\n P0 = 0\n P1 = 0\n P2 = 0\n\nSo: where's that + 3 copy come from, and where does the clear come from?\n\n\nr~","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=erAregxc;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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