<div dir="ltr"><div>There's probably something we can do there. We'd need a scalar pointer in IR to refer to though right? We likely have a vector GEP and none of the underlying APIs know what to do with that. Or we need to change those APIs to refer to a specific element of the vector?</div><div><br></div><div>We'd also need a new base class for the gather and scatter nodes in SelectionDAG other than MemSDNode or we'd need to change MemSDNode to have more than just a single MemOperand pointer.</div><br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">~Craig</div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Mar 18, 2020 at 4:16 PM Philip Reames via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org">llvm-commits@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Just curious, we have the ability to describe multiple memory locations <br>
for a single instruction. Why not simply track each lane independently <br>
and keep the right locations on each half?<br>
<br>
Philip<br>
<br>
On 3/18/20 4:12 PM, Craig Topper via llvm-commits wrote:<br>
> Author: Craig Topper<br>
> Date: 2020-03-18T16:07:15-07:00<br>
> New Revision: c69a4d6bef0a1350f509f35beb450dccc2a6c5e2<br>
><br>
> URL: <a href="https://github.com/llvm/llvm-project/commit/c69a4d6bef0a1350f509f35beb450dccc2a6c5e2" rel="noreferrer" target="_blank">https://github.com/llvm/llvm-project/commit/c69a4d6bef0a1350f509f35beb450dccc2a6c5e2</a><br>
> DIFF: <a href="https://github.com/llvm/llvm-project/commit/c69a4d6bef0a1350f509f35beb450dccc2a6c5e2.diff" rel="noreferrer" target="_blank">https://github.com/llvm/llvm-project/commit/c69a4d6bef0a1350f509f35beb450dccc2a6c5e2.diff</a><br>
><br>
> LOG: [SelectionDAG] When splitting gathers/scatters in type legalization, set MMO size to UnknownSize<br>
><br>
> Gather/scatter don't access one memory location, they access multiple disjoint locations. So using a fixed size isn't accurate. But we don't have a way to represent the true behavior so just use UnknownSize.<br>
><br>
> Previously we "split" the memory VT and use that size for the MMO of each half. But the memory VT is scalar so splitting usually just returned the original scalar VT, but on 32-bit X86 if the scalar VT was i64 it probably returned i32?<br>
><br>
> Differential Revision: <a href="https://reviews.llvm.org/D76388" rel="noreferrer" target="_blank">https://reviews.llvm.org/D76388</a><br>
><br>
> Added:<br>
> <br>
><br>
> Modified:<br>
> llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp<br>
><br>
> Removed:<br>
> <br>
><br>
><br>
> ################################################################################<br>
> diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp<br>
> index 5a4b4c615bc0..09934bbb29fe 100644<br>
> --- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp<br>
> +++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp<br>
> @@ -20,10 +20,11 @@<br>
> //===----------------------------------------------------------------------===//<br>
> <br>
> #include "LegalizeTypes.h"<br>
> +#include "llvm/Analysis/MemoryLocation.h"<br>
> #include "llvm/IR/DataLayout.h"<br>
> #include "llvm/Support/ErrorHandling.h"<br>
> -#include "llvm/Support/raw_ostream.h"<br>
> #include "llvm/Support/TypeSize.h"<br>
> +#include "llvm/Support/raw_ostream.h"<br>
> using namespace llvm;<br>
> <br>
> #define DEBUG_TYPE "legalize-types"<br>
> @@ -1627,11 +1628,6 @@ void DAGTypeLegalizer::SplitVecRes_MGATHER(MaskedGatherSDNode *MGT,<br>
> std::tie(MaskLo, MaskHi) = DAG.SplitVector(Mask, dl);<br>
> }<br>
> <br>
> - EVT MemoryVT = MGT->getMemoryVT();<br>
> - EVT LoMemVT, HiMemVT;<br>
> - // Split MemoryVT<br>
> - std::tie(LoMemVT, HiMemVT) = DAG.GetSplitDestVTs(MemoryVT);<br>
> -<br>
> SDValue PassThruLo, PassThruHi;<br>
> if (getTypeAction(PassThru.getValueType()) == TargetLowering::TypeSplitVector)<br>
> GetSplitVector(PassThru, PassThruLo, PassThruHi);<br>
> @@ -1644,10 +1640,10 @@ void DAGTypeLegalizer::SplitVecRes_MGATHER(MaskedGatherSDNode *MGT,<br>
> else<br>
> std::tie(IndexLo, IndexHi) = DAG.SplitVector(Index, dl);<br>
> <br>
> - MachineMemOperand *MMO = DAG.getMachineFunction().<br>
> - getMachineMemOperand(MGT->getPointerInfo(),<br>
> - MachineMemOperand::MOLoad, LoMemVT.getStoreSize(),<br>
> - Alignment, MGT->getAAInfo(), MGT->getRanges());<br>
> + MachineMemOperand *MMO = DAG.getMachineFunction().getMachineMemOperand(<br>
> + MGT->getPointerInfo(), MachineMemOperand::MOLoad,<br>
> + MemoryLocation::UnknownSize, Alignment, MGT->getAAInfo(),<br>
> + MGT->getRanges());<br>
> <br>
> SDValue OpsLo[] = {Ch, PassThruLo, MaskLo, Ptr, IndexLo, Scale};<br>
> Lo = DAG.getMaskedGather(DAG.getVTList(LoVT, MVT::Other), LoVT, dl, OpsLo,<br>
> @@ -2376,13 +2372,10 @@ SDValue DAGTypeLegalizer::SplitVecOp_MSCATTER(MaskedScatterSDNode *N,<br>
> SDValue Index = N->getIndex();<br>
> SDValue Scale = N->getScale();<br>
> SDValue Data = N->getValue();<br>
> - EVT MemoryVT = N->getMemoryVT();<br>
> unsigned Alignment = N->getOriginalAlignment();<br>
> SDLoc DL(N);<br>
> <br>
> // Split all operands<br>
> - EVT LoMemVT, HiMemVT;<br>
> - std::tie(LoMemVT, HiMemVT) = DAG.GetSplitDestVTs(MemoryVT);<br>
> <br>
> SDValue DataLo, DataHi;<br>
> if (getTypeAction(Data.getValueType()) == TargetLowering::TypeSplitVector)<br>
> @@ -2409,20 +2402,14 @@ SDValue DAGTypeLegalizer::SplitVecOp_MSCATTER(MaskedScatterSDNode *N,<br>
> std::tie(IndexLo, IndexHi) = DAG.SplitVector(Index, DL);<br>
> <br>
> SDValue Lo;<br>
> - MachineMemOperand *MMO = DAG.getMachineFunction().<br>
> - getMachineMemOperand(N->getPointerInfo(),<br>
> - MachineMemOperand::MOStore, LoMemVT.getStoreSize(),<br>
> - Alignment, N->getAAInfo(), N->getRanges());<br>
> + MachineMemOperand *MMO = DAG.getMachineFunction().getMachineMemOperand(<br>
> + N->getPointerInfo(), MachineMemOperand::MOStore,<br>
> + MemoryLocation::UnknownSize, Alignment, N->getAAInfo(), N->getRanges());<br>
> <br>
> SDValue OpsLo[] = {Ch, DataLo, MaskLo, Ptr, IndexLo, Scale};<br>
> Lo = DAG.getMaskedScatter(DAG.getVTList(MVT::Other), DataLo.getValueType(),<br>
> DL, OpsLo, MMO, N->getIndexType());<br>
> <br>
> - MMO = DAG.getMachineFunction().<br>
> - getMachineMemOperand(N->getPointerInfo(),<br>
> - MachineMemOperand::MOStore, HiMemVT.getStoreSize(),<br>
> - Alignment, N->getAAInfo(), N->getRanges());<br>
> -<br>
> // The order of the Scatter operation after split is well defined. The "Hi"<br>
> // part comes after the "Lo". So these two operations should be chained one<br>
> // after another.<br>
><br>
><br>
> <br>
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</blockquote></div>