Re: [Qemu-devel] [PATCH v3 2/7] target/m68k: add fmovecr - Philippe Mathieu-Daudé

From: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
To: Laurent Vivier <laurent@vivier.eu>, qemu-devel@nongnu.org
Cc: Aurelien Jarno <aurelien@aurel32.net>,
	Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH v3 2/7] target/m68k: add fmovecr
Date: Tue, 27 Jun 2017 18:04:15 -0300	[thread overview]
Message-ID: <9fa0ca46-7751-bad7-a18a-c74d9b33c996@amsat.org> (raw)
In-Reply-To: <20170627191221.31650-3-laurent@vivier.eu>

On 06/27/2017 04:12 PM, Laurent Vivier wrote:
> fmovecr moves a floating point constant from the
> FPU ROM to a floating point register.
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> Reviewed-by: Richard Henderson <rth@twiddle.net>
> ---
>   target/m68k/fpu_helper.c | 30 ++++++++++++++++++++++++++++++
>   target/m68k/helper.h     |  1 +
>   target/m68k/translate.c  | 13 ++++++++++++-
>   3 files changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/target/m68k/fpu_helper.c b/target/m68k/fpu_helper.c
> index a9e17f5..912c0b7 100644
> --- a/target/m68k/fpu_helper.c
> +++ b/target/m68k/fpu_helper.c
> @@ -23,6 +23,31 @@
>   #include "exec/helper-proto.h"
>   #include "exec/exec-all.h"
>   
> +static const floatx80 fpu_rom[128] = {

"The values contained at offsets other than those defined above are
reserved for the use of Motorola and may be different on various mask
sets of the floating-point coprocessor. These undefined values yield the
value 0.0 [ floatx80_zero ] in the M68040FPSP."

^ with a such comment around:

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> +    [0x00] = floatx80_pi,                                   /* Pi */
> +    [0x0b] = make_floatx80(0x3ffd, 0x9a209a84fbcff798ULL),  /* Log10(2) */
> +    [0x0c] = make_floatx80(0x4000, 0xadf85458a2bb4a9aULL),  /* e        */
> +    [0x0d] = make_floatx80(0x3fff, 0xb8aa3b295c17f0bcULL),  /* Log2(e)  */
> +    [0x0e] = make_floatx80(0x3ffd, 0xde5bd8a937287195ULL),  /* Log10(e) */
> +    [0x0f] = floatx80_zero,                                 /* Zero     */
> +    [0x30] = floatx80_ln2,                                  /* ln(2)    */
> +    [0x31] = make_floatx80(0x4000, 0x935d8dddaaa8ac17ULL),  /* ln(10)   */
> +    [0x32] = floatx80_one,                                  /* 10^0     */
> +    [0x33] = make_floatx80(0x4002, 0xa000000000000000ULL),  /* 10^1     */
> +    [0x34] = make_floatx80(0x4005, 0xc800000000000000ULL),  /* 10^2     */
> +    [0x35] = make_floatx80(0x400c, 0x9c40000000000000ULL),  /* 10^4     */
> +    [0x36] = make_floatx80(0x4019, 0xbebc200000000000ULL),  /* 10^8     */
> +    [0x37] = make_floatx80(0x4034, 0x8e1bc9bf04000000ULL),  /* 10^16    */
> +    [0x38] = make_floatx80(0x4069, 0x9dc5ada82b70b59eULL),  /* 10^32    */
> +    [0x39] = make_floatx80(0x40d3, 0xc2781f49ffcfa6d5ULL),  /* 10^64    */
> +    [0x3a] = make_floatx80(0x41a8, 0x93ba47c980e98ce0ULL),  /* 10^128   */
> +    [0x3b] = make_floatx80(0x4351, 0xaa7eebfb9df9de8eULL),  /* 10^256   */
> +    [0x3c] = make_floatx80(0x46a3, 0xe319a0aea60e91c7ULL),  /* 10^512   */
> +    [0x3d] = make_floatx80(0x4d48, 0xc976758681750c17ULL),  /* 10^1024  */
> +    [0x3e] = make_floatx80(0x5a92, 0x9e8b3b5dc53d5de5ULL),  /* 10^2048  */
> +    [0x3f] = make_floatx80(0x7525, 0xc46052028a20979bULL),  /* 10^4096  */
> +};
> +
>   int32_t HELPER(reds32)(CPUM68KState *env, FPReg *val)
>   {
>       return floatx80_to_int32(val->d, &env->fp_status);
> @@ -204,3 +229,8 @@ void HELPER(ftst)(CPUM68KState *env, FPReg *val)
>       }
>       env->fpsr = (env->fpsr & ~FPSR_CC_MASK) | cc;
>   }
> +
> +void HELPER(fconst)(CPUM68KState *env, FPReg *val, uint32_t offset)
> +{
> +    val->d = fpu_rom[offset];
> +}
> diff --git a/target/m68k/helper.h b/target/m68k/helper.h
> index 98cbf18..d6e80e4 100644
> --- a/target/m68k/helper.h
> +++ b/target/m68k/helper.h
> @@ -35,6 +35,7 @@ DEF_HELPER_4(fdiv, void, env, fp, fp, fp)
>   DEF_HELPER_FLAGS_3(fcmp, TCG_CALL_NO_RWG, void, env, fp, fp)
>   DEF_HELPER_FLAGS_2(set_fpcr, TCG_CALL_NO_RWG, void, env, i32)
>   DEF_HELPER_FLAGS_2(ftst, TCG_CALL_NO_RWG, void, env, fp)
> +DEF_HELPER_3(fconst, void, env, fp, i32)
>   
>   DEF_HELPER_3(mac_move, void, env, i32, i32)
>   DEF_HELPER_3(macmulf, i64, env, i32, i32)
> diff --git a/target/m68k/translate.c b/target/m68k/translate.c
> index dff604c..0bb3300 100644
> --- a/target/m68k/translate.c
> +++ b/target/m68k/translate.c
> @@ -4518,10 +4518,21 @@ DISAS_INSN(fpu)
>       ext = read_im16(env, s);
>       opmode = ext & 0x7f;
>       switch ((ext >> 13) & 7) {
> -    case 0: case 2:
> +    case 0:
>           break;
>       case 1:
>           goto undef;
> +    case 2:
> +        if (insn == 0xf200 && (ext & 0xfc00) == 0x5c00) {
> +            /* fmovecr */
> +            TCGv rom_offset = tcg_const_i32(opmode);

you could reuse tmp32:

tmp32 = tcg_const_i32(opmode); /* rom offset */

but it's good like that ;)

> +            cpu_dest = gen_fp_ptr(REG(ext, 7));
> +            gen_helper_fconst(cpu_env, cpu_dest, rom_offset);
> +            tcg_temp_free_ptr(cpu_dest);
> +            tcg_temp_free(rom_offset);

Oh this was a leak in v2? I didn't notice.

> +            return;
> +        }
> +        break;
>       case 3: /* fmove out */
>           cpu_src = gen_fp_ptr(REG(ext, 7));
>           opsize = ext_opsize(ext, 10);
> 