[llvm-commits] [llvm] r159876 - in /llvm/trunk: lib/Transforms/InstCombine/InstructionCombining.cpp test/Transforms/InstCombine/badmalloc.ll test/Transforms/InstCombine/invoke.ll test/Transforms/InstCombine/malloc-free-delete.ll test/Transforms/InstCom

[Duncan Sands]

Hi Nuno,

On 08/07/12 22:01, Nuno Lopes wrote:
>>> --- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Fri Jul  6
>>> 18:09:25 2012
>>> @@ -1137,12 +1137,29 @@
>>>         }
>>>       }
>>>       if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
>>> -      if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
>>> -          II->getIntrinsicID() == Intrinsic::lifetime_end) {
>>> +      switch (II->getIntrinsicID()) {
>>> +      default: return false;
>>> +      case Intrinsic::memmove:
>>> +      case Intrinsic::memcpy:
>>> +      case Intrinsic::memset: {
>>> +        MemIntrinsic *MI = cast<MemIntrinsic>(II);
>>> +        if (MI->isVolatile() || MI->getRawDest() != V)
>>
>> why exclude volatile stores?  If all that is being done to the allocated memory
>> is doing a bunch of volatile stores to it, I don't see why you can't discard
>> them and the allocation too.
>
> I thought about that, but.. I guess it's better not to mess around with
> volatiles. And I don't even think it's legal (C standard wise) to remove it.

we already remove volatile stores to alloca's, so why not to heap allocations
too?

Ciao, Duncan.