Reapply "[ARM] Combine base-updating/post-incrementing vector load/stores."

r223862 tried to also combine base-updating load/stores.
r224198 reverted it, as "it created a regression on the test-suite
on test MultiSource/Benchmarks/Ptrdist/anagram by scrambling the order
in which the words are shown."
Reapply, with a fix to ignore non-normal load/stores.
Truncstores are handled elsewhere (you can actually write a pattern for
those, whereas for postinc loads you can't, since they return two values),
but it should be possible to also combine extloads base updates, by checking
that the memory (rather than result) type is of the same size as the addend.

Original commit message:
We used to only combine intrinsics, and turn them into VLD1_UPD/VST1_UPD
when the base pointer is incremented after the load/store.

We can do the same thing for generic load/stores.

Note that we can only combine the first load/store+adds pair in
a sequence (as might be generated for a v16f32 load for instance),
because other combines turn the base pointer addition chain (each
computing the address of the next load, from the address of the last
load) into independent additions (common base pointer + this load's
offset).

Differential Revision: http://reviews.llvm.org/D6585

llvm-svn: 224203

1 files changed, 40 insertions, 6 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 8c893e34164..8208c125374 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -567,6 +567,7 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM)
     setTargetDAGCombine(ISD::FP_TO_SINT);
     setTargetDAGCombine(ISD::FP_TO_UINT);
     setTargetDAGCombine(ISD::FDIV);
+    setTargetDAGCombine(ISD::LOAD);
 
     // It is legal to extload from v4i8 to v4i16 or v4i32.
     MVT Tys[6] = {MVT::v8i8, MVT::v4i8, MVT::v2i8,
@@ -8868,15 +8869,18 @@ static SDValue PerformVECTOR_SHUFFLECombine(SDNode *N, SelectionDAG &DAG) {
                               DAG.getUNDEF(VT), NewMask.data());
 }
 
-/// CombineBaseUpdate - Target-specific DAG combine function for VLDDUP and
-/// NEON load/store intrinsics to merge base address updates.
+/// CombineBaseUpdate - Target-specific DAG combine function for VLDDUP,
+/// NEON load/store intrinsics, and generic vector load/stores, to merge
+/// base address updates.
+/// For generic load/stores, the memory type is assumed to be a vector.
 /// The caller is assumed to have checked legality.
 static SDValue CombineBaseUpdate(SDNode *N,
                                  TargetLowering::DAGCombinerInfo &DCI) {
   SelectionDAG &DAG = DCI.DAG;
   bool isIntrinsic = (N->getOpcode() == ISD::INTRINSIC_VOID ||
                       N->getOpcode() == ISD::INTRINSIC_W_CHAIN);
-  unsigned AddrOpIdx = (isIntrinsic ? 2 : 1);
+  bool isStore = N->getOpcode() == ISD::STORE;
+  unsigned AddrOpIdx = ((isIntrinsic || isStore) ? 2 : 1);
   SDValue Addr = N->getOperand(AddrOpIdx);
 
   // Search for a use of the address operand that is an increment.
@@ -8937,6 +8941,10 @@ static SDValue CombineBaseUpdate(SDNode *N,
       case ARMISD::VLD2DUP: NewOpc = ARMISD::VLD2DUP_UPD; NumVecs = 2; break;
       case ARMISD::VLD3DUP: NewOpc = ARMISD::VLD3DUP_UPD; NumVecs = 3; break;
       case ARMISD::VLD4DUP: NewOpc = ARMISD::VLD4DUP_UPD; NumVecs = 4; break;
+      case ISD::LOAD:       NewOpc = ARMISD::VLD1_UPD;
+        NumVecs = 1; isLaneOp = false; break;
+      case ISD::STORE:      NewOpc = ARMISD::VST1_UPD;
+        NumVecs = 1; isLoad = false; isLaneOp = false; break;
       }
     }
 
@@ -8944,8 +8952,11 @@ static SDValue CombineBaseUpdate(SDNode *N,
     EVT VecTy;
     if (isLoad)
       VecTy = N->getValueType(0);
-    else
+    else if (isIntrinsic)
       VecTy = N->getOperand(AddrOpIdx+1).getValueType();
+    else
+      VecTy = N->getOperand(1).getValueType();
+
     unsigned NumBytes = NumVecs * VecTy.getSizeInBits() / 8;
     if (isLaneOp)
       NumBytes /= VecTy.getVectorNumElements();
@@ -8978,8 +8989,13 @@ static SDValue CombineBaseUpdate(SDNode *N,
     Ops.push_back(N->getOperand(0)); // incoming chain
     Ops.push_back(N->getOperand(AddrOpIdx));
     Ops.push_back(Inc);
-    for (unsigned i = AddrOpIdx + 1; i < N->getNumOperands(); ++i) {
-      Ops.push_back(N->getOperand(i));
+    if (StoreSDNode *StN = dyn_cast<StoreSDNode>(N)) {
+      // Try to match the intrinsic's signature
+      Ops.push_back(StN->getValue());
+      Ops.push_back(DAG.getConstant(StN->getAlignment(), MVT::i32));
+    } else {
+      for (unsigned i = AddrOpIdx + 1; i < N->getNumOperands(); ++i)
+        Ops.push_back(N->getOperand(i));
     }
     MemSDNode *MemInt = cast<MemSDNode>(N);
     SDValue UpdN = DAG.getMemIntrinsicNode(NewOpc, SDLoc(N), SDTys,
@@ -9121,6 +9137,18 @@ static SDValue PerformVDUPLANECombine(SDNode *N,
   return DCI.DAG.getNode(ISD::BITCAST, SDLoc(N), VT, Op);
 }
 
+static SDValue PerformLOADCombine(SDNode *N,
+                                  TargetLowering::DAGCombinerInfo &DCI) {
+  EVT VT = N->getValueType(0);
+
+  // If this is a legal vector load, try to combine it into a VLD1_UPD.
+  if (ISD::isNormalLoad(N) && VT.isVector() &&
+      DCI.DAG.getTargetLoweringInfo().isTypeLegal(VT))
+    return CombineBaseUpdate(N, DCI);
+
+  return SDValue();
+}
+
 /// PerformSTORECombine - Target-specific dag combine xforms for
 /// ISD::STORE.
 static SDValue PerformSTORECombine(SDNode *N,
@@ -9261,6 +9289,11 @@ static SDValue PerformSTORECombine(SDNode *N,
                         St->getAAInfo());
   }
 
+  // If this is a legal vector store, try to combine it into a VST1_UPD.
+  if (ISD::isNormalStore(N) && VT.isVector() &&
+      DCI.DAG.getTargetLoweringInfo().isTypeLegal(VT))
+    return CombineBaseUpdate(N, DCI);
+
   return SDValue();
 }
 
@@ -9852,6 +9885,7 @@ SDValue ARMTargetLowering::PerformDAGCombine(SDNode *N,
   case ISD::ANY_EXTEND: return PerformExtendCombine(N, DCI.DAG, Subtarget);
   case ISD::SELECT_CC:  return PerformSELECT_CCCombine(N, DCI.DAG, Subtarget);
   case ARMISD::CMOV: return PerformCMOVCombine(N, DCI.DAG);
+  case ISD::LOAD:       return PerformLOADCombine(N, DCI);
   case ARMISD::VLD2DUP:
   case ARMISD::VLD3DUP:
   case ARMISD::VLD4DUP: