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

To easily compare with the SH4 manual, rename:

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

Mention how overflow is calculated.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Message-Id: <20240430163125.77430-4-philmd@linaro.org>

diff --git a/target/sh4/translate.c b/target/sh4/translate.c
index 3e013b7c7c5b5cdbdf8baea1ca941bb0eee67619..47c0f3404e8eea14d5070282d7b378dfd6500399 100644 (file)
--- a/target/sh4/translate.c
+++ b/target/sh4/translate.c
@@ -705,16 +705,20 @@ static void _decode_opc(DisasContext * ctx)
         return;
     case 0x300f: /* addv Rm,Rn */
         {
-            TCGv t0, t1, t2;
-            t0 = tcg_temp_new();
-            tcg_gen_add_i32(t0, REG(B7_4), REG(B11_8));
+            TCGv Rn = REG(B11_8);
+            TCGv Rm = REG(B7_4);
+            TCGv result, t1, t2;
+
+            result = tcg_temp_new();
             t1 = tcg_temp_new();
-            tcg_gen_xor_i32(t1, t0, REG(B11_8));
             t2 = tcg_temp_new();
-            tcg_gen_xor_i32(t2, REG(B7_4), REG(B11_8));
+            tcg_gen_add_i32(result, Rm, Rn);
+            /* T = ((Rn ^ Rm) & (Result ^ Rn)) >> 31 */
+            tcg_gen_xor_i32(t1, result, Rn);
+            tcg_gen_xor_i32(t2, Rm, Rn);
             tcg_gen_andc_i32(cpu_sr_t, t1, t2);
             tcg_gen_shri_i32(cpu_sr_t, cpu_sr_t, 31);
-            tcg_gen_mov_i32(REG(B11_8), t0);
+            tcg_gen_mov_i32(Rn, result);
         }
         return;
     case 0x2009: /* and Rm,Rn */