[PATCH] D59795: [DAGCombine] Improve Lifetime node chains.

[Nirav Dave via Phabricator via llvm-commits]

niravd updated this revision to Diff 192682.
niravd added a comment.

Now that lifetime node hashing and TokenFactor cleanup has happened, factor out Dead Store improvements as they are no longer needed to prevent regressions.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59795/new/

https://reviews.llvm.org/D59795

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/X86/swap.ll


Index: llvm/test/CodeGen/X86/swap.ll
===================================================================
--- llvm/test/CodeGen/X86/swap.ll
+++ llvm/test/CodeGen/X86/swap.ll
@@ -94,7 +94,6 @@
 ; AA-LABEL: twoallocs:
 ; AA:       # %bb.0: # %entry
 ; AA-NEXT:    vmovups (%rdi), %xmm0
-; AA-NEXT:    vmovaps %xmm0, -{{[0-9]+}}(%rsp)
 ; AA-NEXT:    vmovups %xmm0, (%rsi)
 ; AA-NEXT:    retq
 entry:
@@ -125,7 +124,6 @@
 ; AA-LABEL: onealloc_readback_1:
 ; AA:       # %bb.0: # %entry
 ; AA-NEXT:    vmovups (%rsi), %xmm0
-; AA-NEXT:    vmovaps %xmm0, -{{[0-9]+}}(%rsp)
 ; AA-NEXT:    vmovups %xmm0, (%rdi)
 ; AA-NEXT:    retq
 entry:
@@ -155,7 +153,6 @@
 ; AA-LABEL: onealloc_readback_2:
 ; AA:       # %bb.0: # %entry
 ; AA-NEXT:    vmovups (%rsi), %xmm0
-; AA-NEXT:    vmovaps %xmm0, -{{[0-9]+}}(%rsp)
 ; AA-NEXT:    vmovups %xmm0, (%rdi)
 ; AA-NEXT:    retq
 entry:
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -384,6 +384,10 @@
     SDValue replaceStoreOfFPConstant(StoreSDNode *ST);
 
     SDValue visitSTORE(SDNode *N);
+
+    SDValue ImproveLifetimeNodeChain(SDNode *N);
+
+    SDValue visitLIFETIME_START(SDNode *N);
     SDValue visitLIFETIME_END(SDNode *N);
     SDValue visitINSERT_VECTOR_ELT(SDNode *N);
     SDValue visitEXTRACT_VECTOR_ELT(SDNode *N);
@@ -1604,6 +1608,7 @@
   case ISD::MLOAD:              return visitMLOAD(N);
   case ISD::MSCATTER:           return visitMSCATTER(N);
   case ISD::MSTORE:             return visitMSTORE(N);
+  case ISD::LIFETIME_START:     return visitLIFETIME_START(N);
   case ISD::LIFETIME_END:       return visitLIFETIME_END(N);
   case ISD::FP_TO_FP16:         return visitFP_TO_FP16(N);
   case ISD::FP16_TO_FP:         return visitFP16_TO_FP(N);
@@ -15645,7 +15650,32 @@
   return ReduceLoadOpStoreWidth(N);
 }
 
+SDValue DAGCombiner::ImproveLifetimeNodeChain(SDNode *N) {
+  auto Chain = N->getOperand(0);
+  auto NewChain = FindBetterChain(N, Chain);
+  if (NewChain != Chain) {
+    SDNode *N2 = DAG.UpdateNodeOperands(N, NewChain, N->getOperand(1));
+    // Make sure users of new N still depend on Chain
+    auto TF = DAG.getNode(ISD::TokenFactor, SDLoc(N2), MVT::Other, Chain,
+                          SDValue(N2, 0));
+    DAG.ReplaceAllUsesOfValueWith(SDValue(N2, 0), TF);
+    AddToWorklist(DAG.UpdateNodeOperands(TF.getNode(), Chain, SDValue(N2, 0)));
+    AddToWorklist(N2);
+    return SDValue(N, 0);
+  }
+  return SDValue();
+}
+
+SDValue DAGCombiner::visitLIFETIME_START(SDNode *N) {
+  if (SDValue V = ImproveLifetimeNodeChain(N))
+    return V;
+  return SDValue();
+}
+
 SDValue DAGCombiner::visitLIFETIME_END(SDNode *N) {
+  if (SDValue V = ImproveLifetimeNodeChain(N))
+    return V;
+
   const auto *LifetimeEnd = cast<LifetimeSDNode>(N);
   if (!LifetimeEnd->hasOffset())
     return SDValue();


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