On 5/23/2023 8:45 AM, Richard Henderson wrote:
> On 5/18/23 06:57, Fei Wu wrote:
>> +void HELPER(inc_exec_freq)(void *ptr)
>> +{
>> + TBStatistics *stats = (TBStatistics *) ptr;
>> + tcg_debug_assert(stats);
>> + ++stats->executions.normal;
>> +}
> ...
>> +static inline void gen_tb_exec_count(TranslationBlock *tb)
>> +{
>> + if (tb_stats_enabled(tb, TB_EXEC_STATS)) {
>> + TCGv_ptr ptr = tcg_temp_new_ptr();
>> + tcg_gen_movi_ptr(ptr, (intptr_t)tb->tb_stats);
>> + gen_helper_inc_exec_freq(ptr);
>> + }
>> +}
>
> This is 3 host instructions, easily expanded inline:
>
> --- a/accel/tcg/translator.c
> +++ b/accel/tcg/translator.c
> @@ -11,6 +11,7 @@
> #include "qemu/error-report.h"
> #include "tcg/tcg.h"
> #include "tcg/tcg-op.h"
> +#include "tcg/tcg-temp-internal.h"
> #include "exec/exec-all.h"
> #include "exec/gen-icount.h"
> #include "exec/log.h"
> @@ -18,6 +19,30 @@
> #include "exec/plugin-gen.h"
> #include "exec/replay-core.h"
>
> +
> +static void gen_tb_exec_count(TranslationBlock *tb)
> +{
> + if (tb_stats_enabled(tb, TB_EXEC_STATS)) {
> + TCGv_ptr ptr = tcg_temp_ebb_new_ptr();
> +
> + tcg_gen_movi_ptr(ptr, (intptr_t)&tb->tb_stats->executions.normal);
> + if (sizeof(tb->tb_stats->executions.normal) == 4) {
> + TCGv_i32 t = tcg_temp_ebb_new_i32();
> + tcg_gen_ld_i32(t, ptr, 0);
> + tcg_gen_addi_i32(t, t, 1);
> + tcg_gen_st_i32(t, ptr, 0);
> + tcg_temp_free_i32(t);
> + } else {
> + TCGv_i64 t = tcg_temp_ebb_new_i64();
> + tcg_gen_ld_i64(t, ptr, 0);
> + tcg_gen_addi_i64(t, t, 1);
> + tcg_gen_st_i64(t, ptr, 0);
> + tcg_temp_free_i64(t);
> + }
> + tcg_temp_free_ptr(ptr);
> + }
> +}
> +
> bool translator_use_goto_tb(DisasContextBase *db, target_ulong dest)
> {
> /* Suppress goto_tb if requested. */
>
>
> I'm not expecially keen on embedding the TBStatistics pointer directly
> like this; for most hosts we will have to put this constant into the
> constant pool. Whereas the pointer already exists at tb->tb_stats, and
> tb is at a constant displacement prior to the code, so we already have
> mechanisms for generating pc-relative addresses.
>
> However, that's premature optimization. Let's get it working first.
>
Here is the coremark results on a 4c qemu-system-riscv64, coremark takes
1cpu in this test.
(tb_stats stop) Iterations/Sec : 5358.012664
(tb_stats start all)
helper - qatomic_inc(normal) Iterations/Sec : 2416.626390
helper - ++normal Iterations/Sec : 4307.559767
no helper - inline add Iterations/Sec : 5168.930031
Also if coremark runs on 4cpu, tb_stats will cost much more even in the
inline case, it's an extreme case though.
Thanks,
Fei.
>
> r~
>
