[LLVMdev] Address space information dropped

[Ivan Llopard]

Le 08/05/2012 20:44, Eli Friedman a écrit :
> On Tue, May 8, 2012 at 4:59 AM, Ivan Llopard<ivanllopard at gmail.com>  wrote:
>> Hi Eli,
>>
>>
>> On 07/05/2012 18:15, Eli Friedman wrote:
>>> On Mon, May 7, 2012 at 5:15 AM, Ivan Llopard<ivanllopard at gmail.com>
>>>   wrote:
>>>> Hi all,
>>>>
>>>> Tuning my TargetAsmPrinter implementation in the back-end side, I
>>>> discovered that the address space number is not passed down while
>>>> emitting global variables with constant initializers. The information is
>>>> dropped at AsmPrinter::EmitGlobalConstant() function call which defaults
>>>> it to zero.
>>>
>>> This sounds like a bug.
>>
>> The feature added to allow targets emit custom data directives based on the
>> address space seems to be broken. However, it doesn't produce any odd
>> behavior because it's not used.
>> The attached patch is quite small and shows where the address space
>> information is getting lost and it will correctly propagate it. It also
>> avoids existent back-ends to break because of an unimplemented hook in
>> MCAsmInfo.
> @@ -1046,7 +1046,8 @@
>         if (CPE.isMachineConstantPoolEntry())
>           EmitMachineConstantPoolValue(CPE.Val.MachineCPVal);
>         else
> -        EmitGlobalConstant(CPE.Val.ConstVal);
> +        EmitGlobalConstant(CPE.Val.ConstVal, (isa<PointerType>(Ty)) ?
> +            cast<PointerType>(Ty)->getAddressSpace() : 0);
>       }
>     }
>   }
>
> This looks suspicious; how can an entry in the constant pool possibly
> acquire an address space based on the type of the value?

IIUC, global values are also constants, I added that verification just 
in case. But I agree that it's may be unrealistic.

Ivan

>
> -Eli