Zouqiong,
LIR is very lowlevel representation and you are allowed to use only x86
commands. See "Pentium4. Instruction reference set" for instructions details
every time you are not sure in results.
The problem is that you can't encode mov [mem], [mem] in a single
instruction and have to use 2 instructions and intermediate value here.
Did I understand your problem right?
On 2/1/07, zouqiong <[EMAIL PROTECTED]> wrote:
2007/2/1, Mikhail Fursov <[EMAIL PROTECTED]>:
>
> Hi Zouqiong,
> here are answers:
>
> On 1/31/07, zouqiong <[EMAIL PROTECTED]> wrote:
> >
> > Sorry, I still have two questions.
> > 1.
> >
> > What is the difference between newOpnd, newImmOpnd and newMemOpnd?
>
>
> Here is an extraction from sources that describes the difference:
> Opnd * IRManager::newImmOpnd(Type * type, int64 immediate)
> {
> Opnd * opnd = newOpnd(type);
> opnd->assignImmValue(immediate);
> return opnd;
> }
>
> Opnd * IRManager::newMemOpnd(Type * type, MemOpndKind k, Opnd * base,
Opnd
> *
> index, Opnd * scale, Opnd * displacement, RegName segReg)
> {
> Opnd * opnd = newOpnd(type);
> opnd->assignMemLocation(k,base,index,scale,displacement);
> if (segReg != RegName_Null)
> opnd->setSegReg(segReg);
> return opnd;
> }
>
>
> So newImmOpnd and newMemOpnd are simple wrappers for newOpnd
>
>
>
> Opnd* baseOpnd= irManager.newImmOpnd(typeManager.getUnmanagedPtrType(
> > typeManager.getUIntPtrType()),
> > (POINTER_SIZE_INT)¤t_obj_acc_record_pointer);
> > Opnd* RefOpnd = irManager.newMemOpnd(typeManager.getUIntPtrType(),
> > MemOpndKind_Heap,
> > baseOpnd_current_obj_acc_record_pointer, NULL, NULL, NULL);
> > appendInsts(irManager.newCopyPseudoInst(Mnemonic_MOV, RefOpnd,
> > (Opnd*)elemBase));
> >
> >
> > Opnd* memOpnd = irManager.newMemOpnd(typeManager.getUIntPtrType(),
> > MemOpndKind_Heap,
> > baseOpnd_current_obj_acc_record_pointer, NULL, NULL, NULL);
> > appendInsts(irManager.newInst(Mnemonic_SUB,memOpnd,
irManager.newImmOpnd
> (
> > typeManager.getUInt32Type(), 16)));
> >
> >
> > What's the difference between memOpnd and baseOpnd?
>
>
> Mem-opnd contains up to 4 opnds: base,index,scale,and displacement. So
> mem-opnd is used to support complex address form in LIR.
>
>
> I look the code emitted as below, It seems that they have no
difference.
> >
> > mov 0xb40534, %esi
> > mov %ebp, (%esi)
> >
> > mov 0xb40534, %ebp
> > subl 0x10, 0x0(%ebp)
> >
> > 2. If I want to generate such code:
> > mov 0xb400534, %esi
> > mov (%esi), %esi
> >
> > How should I write the LIR?
>
>
> If you want to preserve register, use newRegOpnd with the register name.
> It
> will add additional constraint to opnd.
> If you want save value by address, create new mem-opnd with a base opnd
> contains address and use newCopyPseudoInst to put new value to the
address
> represented by mem-opnd.
>
>
> Feel free to ask more if you have questions..
> --
> Mikhail Fursov
>
Thanks, Mikhail, you are very very very kind! :-)
I want to use value load from some address to index the memory.
Opnd* baseOpnd = irManager.newImmOpnd(typeManager.getUnmanagedPtrType(
typeManager.getUIntPtrType()), (POINTER_SIZE_INT)&Address);
Opnd* memOpnd = irManager.newMemOpnd(typeManager.getUIntPtrType
(),MemOpndKind_Heap,baseOpnd,NULL, NULL, NULL);
memOpnd means Address, right?
I want to write to the memory pointed by Address. But I can't use the
memOpnd as a base opnd of a mem opnd.
In fact
Opnd* RefOpnd =
irManager.newMemOpnd(typeManager.getUIntPtrType(),MemOpndKind_Heap,
memOpnd, NULL, NULL, NULL);
will cause error.
I don't know whether I have expressed myself rightly.
Thanks
Qiong
--
Best Regards,
Qiong,Zou
--
Mikhail Fursov
