On Sun, Jan 14, 2018 at 5:41 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
> On Sun, Jan 14, 2018 at 8:39 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
>> On Sun, Jan 14, 2018 at 5:35 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>>> On Sun, Jan 14, 2018 at 8:19 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
>>>> On Fri, Jan 12, 2018 at 9:01 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
>>>>> On Thu, Jan 11, 2018 at 2:28 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
>>>>>
>>>>>> Hi Uros,
>>>>>>
>>>>>> Can you take a look at my x86 backend changes so that they are ready
>>>>>> to check in once we have consensus.
>>>>>
>>>>> Please finish the talks about the correct approach first. Once the
>>>>> consensus is reached, please post the final version of the patches for
>>>>> review.
>>>>>
>>>>> BTW: I have no detailed insight in these issues, so I'll look mostly
>>>>> at the implementation details, probably early next week.
>>>>
>>>> One general remark is on the usage of -1 as an invalid register
>>>
>>> This has been rewritten. The checked in patch no longer does that.
>>
>> Another issue:
>>
>> +static void
>> +indirect_thunk_name (char name[32], int regno, bool need_bnd_p)
>> +{
>> + if (USE_HIDDEN_LINKONCE)
>> + {
>> + const char *bnd = need_bnd_p ? "_bnd" : "";
>> + if (regno >= 0)
>> + {
>> + const char *reg_prefix;
>> + if (LEGACY_INT_REGNO_P (regno))
>> + reg_prefix = TARGET_64BIT ? "r" : "e";
>> + else
>> + reg_prefix = "";
>> + sprintf (name, "__x86_indirect_thunk%s_%s%s",
>> + bnd, reg_prefix, reg_names[regno]);
>> + }
>> + else
>> + sprintf (name, "__x86_indirect_thunk%s", bnd);
>> + }
>>
>> What is the benefit of reg_prefix? Can't we just live with e.g.:
>>
>> __x86_indirect_thunk_ax
>>
>> which is the true register name and is valid for 32bit and 64bit targets.
>
> They are used in asm statements in kernel:
>
> extern void (*func_p) (void);
>
> void
> foo (void)
> {
> asm ("call __x86_indirect_thunk_%V0" : : "a" (func_p));
> }
>
> it generates:
>
> foo:
> movq func_p(%rip), %rax
> call __x86_indirect_thunk_rax
> ret
Please fix %V to output reg_name instead.
Uros.
