[llvm-commits] Request for Review - avoid register pressure with read/modify/write instructions

[Joel Jones]

I have made the changes as requested and have attached the diff.

Joel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: X86OISelDAGToDAG.cpp.diff
Type: application/octet-stream
Size: 5889 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20120327/a40eb9ce/attachment.obj>
-------------- next part --------------


On Mar 27, 2012, at 10:58 AM, Evan Cheng wrote:

> Comments:
> 
> I know some of the issues were there before your patch. But please correct them while you are at it.
> 
> Can you add some comments to isLdIncOrDecSt? There should be at least top level comments. Also I think there is a bug in this. Please check if the load is a non-indexed, non-extending load (using isNormalLoad()). Similarly, please  make sure the store is not a truncating store.
> 
> int memSize = StoreNode->getMemOperand()->getSize();
> Please do not depend on memoperand for this. LSBaseSDNode has MemVT field. Or better yet, just use Load's ValueType. So replace
> 
> +    if (!(memSize == 8 || memSize == 4 || memSize == 2 || memSize == 1)) 
> +        return false;
> 
> with something like:
> if (LdVT != MVT::i8 && LdVT != MVT::i16 && LdVT != MVT::i32 && LdVT != MVT::i64)
>  return false;
> 
> newIncDecOpc() has some formatting issues. Indentation width should be 2.
> 
> One more nitpick. The names for these functions look weird. How about isLoadIncDecStore? getFusedLdStOpcode?
> 
> Evan
> 
> On Mar 26, 2012, at 6:01 PM, Joel Jones <joel_k_jones at apple.com> wrote:
> 
>> This is a code change to add support for changing instruction sequences of the form:
>> load
>> inc/dec of 8/16/32/64 bits
>> store
>> into the appropriate X86 inc/dec instruction:
>> inc[qlwb]/dec[qlwb]
>> 
>> The change is in lib/Target/X86/X86ISelDAGToDAG.cpp, an svn diff of which is attached.
>> Also attached is a test case.
>> 
>> Joel Jones
>> 
>> <X86OISelDAGToDAG.cpp.diff><readModWrite.ll>_______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>