The documentation says: SUBV Rm, Rn Rn - Rm -> Rn, underflow -> T
While correctly performing the substraction, the underflow is not detected. While we can check the high xored bit for overflow, for underflow we need to check the xored value is not negative. Cc: [email protected] Fixes: ad8d25a11f ("target-sh4: implement addv and subv using TCG") Reported-by: Paul Cercueil <[email protected]> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2318 Signed-off-by: Philippe Mathieu-Daudé <[email protected]> --- target/sh4/translate.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/target/sh4/translate.c b/target/sh4/translate.c index 4a1dd0d1f4..1c48d8ebea 100644 --- a/target/sh4/translate.c +++ b/target/sh4/translate.c @@ -937,7 +937,7 @@ static void _decode_opc(DisasContext * ctx) t2 = tcg_temp_new(); tcg_gen_xor_i32(t2, REG(B11_8), REG(B7_4)); tcg_gen_and_i32(t1, t1, t2); - tcg_gen_shri_i32(cpu_sr_t, t1, 31); + tcg_gen_setcondi_i32(TCG_COND_GE, cpu_sr_t, t1, 0); tcg_gen_mov_i32(REG(B11_8), t0); } return; -- 2.41.0
