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target/sh4: Rename TCGv variables as manual for SUBV opcode 

To easily compare with the SH4 manual, rename:

  REG(B11_8) -> Rn
  REG(B7_4) -> Rm
  t0 -> result

Mention how underflow is calculated.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20240430163125.77430-5-philmd@linaro.org>
This commit is contained in:
Philippe Mathieu-Daudé 2024-04-30 16:43:09 +02:00
parent 40ed073f89
commit 942ba09d7c
1 changed files with 10 additions and 6 deletions
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16
target/sh4/translate.c
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@ -933,16 +933,20 @@ static void _decode_opc(DisasContext * ctx)
return; return;
case 0x300b: /* subv Rm,Rn */ case 0x300b: /* subv Rm,Rn */
{ {
TCGv t0, t1, t2; TCGv Rn = REG(B11_8);
t0 = tcg_temp_new(); TCGv Rm = REG(B7_4);
tcg_gen_sub_i32(t0, REG(B11_8), REG(B7_4)); TCGv result, t1, t2;
result = tcg_temp_new();
t1 = tcg_temp_new(); t1 = tcg_temp_new();
tcg_gen_xor_i32(t1, t0, REG(B11_8));
t2 = tcg_temp_new(); t2 = tcg_temp_new();
tcg_gen_xor_i32(t2, REG(B11_8), REG(B7_4)); tcg_gen_sub_i32(result, Rn, Rm);
/* T = ((Rn ^ Rm) & (Result ^ Rn)) >> 31 */
tcg_gen_xor_i32(t1, result, Rn);
tcg_gen_xor_i32(t2, Rn, Rm);
tcg_gen_and_i32(t1, t1, t2); tcg_gen_and_i32(t1, t1, t2);
tcg_gen_shri_i32(cpu_sr_t, t1, 31); tcg_gen_shri_i32(cpu_sr_t, t1, 31);
tcg_gen_mov_i32(REG(B11_8), t0); tcg_gen_mov_i32(Rn, result);
} }
return; return;
case 0x2008: /* tst Rm,Rn */ case 0x2008: /* tst Rm,Rn */