On 19 April 2016 at 19:07, Sergey Sorokin <afaral...@yandex.ru> wrote:
> There is a duplicating code in AArch32 exception return implementation.
> The patch rearranges the code to avoid this.
>
> Signed-off-by: Sergey Sorokin <afaral...@yandex.ru>
> ---
> target-arm/translate.c | 36 +++++++++++++++++++++---------------
> 1 file changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/target-arm/translate.c b/target-arm/translate.c
> index 940ec8d..68671b7 100644
> --- a/target-arm/translate.c
> +++ b/target-arm/translate.c
> @@ -4349,24 +4349,27 @@ static void gen_mrs_banked(DisasContext *s, int r,
> int sysm, int rn)
> s->is_jmp = DISAS_UPDATE;
> }
>
> -/* Generate an old-style exception return. Marks pc as dead. */
> -static void gen_exception_return(DisasContext *s, TCGv_i32 pc)
> +/* Generate an exception return. Marks both values as dead. */
> +static void gen_exception_return_internal(DisasContext *s, TCGv_i32 pc,
> + TCGv_i32 cpsr)
> {
> - TCGv_i32 tmp;
> + gen_helper_cpsr_write_eret(cpu_env, cpsr);
> + tcg_temp_free_i32(cpsr);
> store_reg(s, 15, pc);
> - tmp = load_cpu_field(spsr);
> - gen_helper_cpsr_write_eret(cpu_env, tmp);
> - tcg_temp_free_i32(tmp);
> s->is_jmp = DISAS_JUMP;
> }
>
> +/* Generate an old-style exception return. Marks pc as dead. */
> +static void gen_exception_return(DisasContext *s, TCGv_i32 pc)
> +{
> + TCGv_i32 tmp = load_cpu_field(spsr);
> + gen_exception_return_internal(s, pc, tmp);
> +}
> +
> /* Generate a v6 exception return. Marks both values as dead. */
> static void gen_rfe(DisasContext *s, TCGv_i32 pc, TCGv_i32 cpsr)
> {
> - gen_helper_cpsr_write_eret(cpu_env, cpsr);
> - tcg_temp_free_i32(cpsr);
> - store_reg(s, 15, pc);
> - s->is_jmp = DISAS_JUMP;
> + gen_exception_return_internal(s, pc, cpsr);
> }
This rearrangement of code is OK.
> static void gen_nop_hint(DisasContext *s, int val)
> @@ -9378,11 +9381,14 @@ static void disas_arm_insn(DisasContext *s, unsigned
> int insn)
> store_reg(s, rn, loaded_var);
> }
> if (exc_return) {
> - /* Restore CPSR from SPSR. */
> - tmp = load_cpu_field(spsr);
> - gen_helper_cpsr_write_eret(cpu_env, tmp);
> - tcg_temp_free_i32(tmp);
> - s->is_jmp = DISAS_JUMP;
> + /* Restore CPSR from SPSR.
> + * Since gen_exception_return() function updates r15
> + * we need just pass current r15 value into it.
> + */
> + tmp = tcg_temp_new_i32();
> + tcg_gen_mov_i32(tmp, cpu_R[15]);
> + /* It marks tmp as dead. */
> + gen_exception_return(s, tmp);
Won't this now emit TCG ops to load the PC from the state struct,
AND it with ~1, and then write it back again ? That seebms worse than the
current code.
> }
> }
> break;
thanks
-- PMM
