Re: [Qemu-devel] [PATCH v5 1/9] tcg: pass down TranslationBlock to tcg_code_gen

[Alex Bennée]

Richard Henderson <address@hidden> writes:

> On 02/05/2016 01:56 AM, Alex Bennée wrote:
>> diff --git a/translate-all.c b/translate-all.c
>> index ab61fac..dce00d5 100644
>> --- a/translate-all.c
>> +++ b/translate-all.c
>> @@ -1055,7 +1055,6 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>>       TranslationBlock *tb;
>>       tb_page_addr_t phys_pc, phys_page2;
>>       target_ulong virt_page2;
>> -    tcg_insn_unit *gen_code_buf;
>>       int gen_code_size, search_size;
>>   #ifdef CONFIG_PROFILER
>>       int64_t ti;
>> @@ -1078,8 +1077,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>>           tcg_ctx.tb_ctx.tb_invalidated_flag = 1;
>>       }
>>
>> -    gen_code_buf = tcg_ctx.code_gen_ptr;
>> -    tb->tc_ptr = gen_code_buf;
>> +    tb->tc_ptr = tcg_ctx.code_gen_ptr;
>
> Why get rid of the gen_code_buf variable?  You're forcing the compiler to keep
> reloading the value from memory.
>
> Certainly that's not relevant to passing down TB to tcg_gen_code, and is a
> separate change that ought to be separately defended.

Fixed. Thanks.

>
>
> r~
>
>>       tb->cs_base = cs_base;
>>       tb->flags = flags;
>>       tb->cflags = cflags;
>> @@ -1119,11 +1117,11 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>>          the tcg optimization currently hidden inside tcg_gen_code.  All
>>          that should be required is to flush the TBs, allocate a new TB,
>>          re-initialize it per above, and re-do the actual code generation.  
>> */
>> -    gen_code_size = tcg_gen_code(&tcg_ctx, gen_code_buf);
>> +    gen_code_size = tcg_gen_code(&tcg_ctx, tb);
>>       if (unlikely(gen_code_size < 0)) {
>>           goto buffer_overflow;
>>       }
>> -    search_size = encode_search(tb, (void *)gen_code_buf + gen_code_size);
>> +    search_size = encode_search(tb, (void *)tb->tc_ptr + gen_code_size);
>>       if (unlikely(search_size < 0)) {
>>           goto buffer_overflow;
>>       }
>> @@ -1145,7 +1143,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>>   #endif
>>
>>       tcg_ctx.code_gen_ptr = (void *)
>> -        ROUND_UP((uintptr_t)gen_code_buf + gen_code_size + search_size,
>> +        ROUND_UP((uintptr_t)tb->tc_ptr + gen_code_size + search_size,
>>                    CODE_GEN_ALIGN);
>>
>>       /* check next page if needed */
>>


--
Alex Bennée