[llvm-commits] [126488] Fix PR1352 and CFrontend/2007-04-24-VolatileStructCopy.c

[Chris Lattner]

On Apr 24, 2007, at 11:48 PM, Duncan Sands wrote:

> Hi Chris,
>
>>      // Non-bitfield aggregate value.
>> -    Emit(TREE_OPERAND(exp, 1), LV.Ptr);
>> -    if (DestLoc)
>> +    if (DestLoc) {
>> +      Emit(TREE_OPERAND(exp, 1), LV.Ptr);
>>        EmitAggregateCopy(DestLoc, LV.Ptr, TREE_TYPE(exp),  
>> isVolatile, false);
>
> why is this ^^^ right?

Possibly not, I was trying to preserve current behavior, because I  
don't have a testcase.

> Doesn't a non-null DestLoc mean you are doing something
> like: A = (B = C), where DestLoc represents A, and the current  
> MODIFY_EXPR
> represents B=C?

Yes, something like that.

> If so, then the above is bogus: isVolatile says whether writes
> to B are volatile, not writes to A: if isVolatile is true, then you  
> are doing
> a volatile write to A, which may or may not need it, and a non- 
> volatile write
> to B when a volatile write is needed!

Right,

-Chris