Commit 354119b4 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r310604: 

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r310604 | niravd | 2017-08-10 08:12:32 -0700 (Thu, 10 Aug 2017) | 13 lines

[X86] Keep dependencies when constructing loads in combineStore

Summary:
Preserve chain dependecies between old and new loads constructed to
prevent loads from reordering below later stores.

Fixes PR34088.

Reviewers: craig.topper, spatel, RKSimon, efriedma

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D36528
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llvm-svn: 310678
parent 6257aa2a

llvm/include/llvm/CodeGen/SelectionDAG.h

+3 −2
Original line number Diff line number Diff line
@@ -1220,8 +1220,9 @@ public: 
  /// If an existing load has uses of its chain, create a token factor node with

  /// that chain and the new memory node's chain and update users of the old

  /// chain to the token factor. This ensures that the new memory node will have

  /// the same relative memory dependency position as the old load.

  void makeEquivalentMemoryOrdering(LoadSDNode *Old, SDValue New);

  /// the same relative memory dependency position as the old load. Returns the

  /// new merged load chain.

  SDValue makeEquivalentMemoryOrdering(LoadSDNode *Old, SDValue New);



  /// Topological-sort the AllNodes list and a

  /// assign a unique node id for each node in the DAG based on their

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

+6 −5
Original line number Diff line number Diff line
@@ -7262,22 +7262,23 @@ void SelectionDAG::TransferDbgValues(SDValue From, SDValue To) { 
    AddDbgValue(I, ToNode, false);

}



void SelectionDAG::makeEquivalentMemoryOrdering(LoadSDNode *OldLoad,

SDValue SelectionDAG::makeEquivalentMemoryOrdering(LoadSDNode *OldLoad,

                                                   SDValue NewMemOp) {

  assert(isa<MemSDNode>(NewMemOp.getNode()) && "Expected a memop node");

  if (!OldLoad->hasAnyUseOfValue(1))

    return;



  // The new memory operation must have the same position as the old load in

  // terms of memory dependency. Create a TokenFactor for the old load and new

  // memory operation and update uses of the old load's output chain to use that

  // TokenFactor.

  SDValue OldChain = SDValue(OldLoad, 1);

  SDValue NewChain = SDValue(NewMemOp.getNode(), 1);

  if (!OldLoad->hasAnyUseOfValue(1))

    return NewChain;



  SDValue TokenFactor =

      getNode(ISD::TokenFactor, SDLoc(OldLoad), MVT::Other, OldChain, NewChain);

  ReplaceAllUsesOfValueWith(OldChain, TokenFactor);

  UpdateNodeOperands(TokenFactor.getNode(), OldChain, NewChain);

  return TokenFactor;

}



//===----------------------------------------------------------------------===//

llvm/lib/Target/X86/X86ISelLowering.cpp

+6 −4
Original line number Diff line number Diff line
@@ -33386,7 +33386,8 @@ static SDValue combineStore(SDNode *N, SelectionDAG &DAG, 
      SDValue NewLd = DAG.getLoad(LdVT, LdDL, Ld->getChain(), Ld->getBasePtr(),

                                  Ld->getPointerInfo(), Ld->getAlignment(),

                                  Ld->getMemOperand()->getFlags());

      SDValue NewChain = NewLd.getValue(1);

      // Make sure new load is placed in same chain order.

      SDValue NewChain = DAG.makeEquivalentMemoryOrdering(Ld, NewLd);

      if (TokenFactorIndex >= 0) {

        Ops.push_back(NewChain);

        NewChain = DAG.getNode(ISD::TokenFactor, LdDL, MVT::Other, Ops);
@@ -33407,11 +33408,12 @@ static SDValue combineStore(SDNode *N, SelectionDAG &DAG, 
                               Ld->getPointerInfo().getWithOffset(4),

                               MinAlign(Ld->getAlignment(), 4),

                               Ld->getMemOperand()->getFlags());

    // Make sure new loads are placed in same chain order.

    SDValue NewChain = DAG.makeEquivalentMemoryOrdering(Ld, LoLd);

    NewChain = DAG.makeEquivalentMemoryOrdering(Ld, HiLd);













    SDValue NewChain = LoLd.getValue(1);















    if (TokenFactorIndex >= 0) {













      Ops.push_back(LoLd);













      Ops.push_back(HiLd);













      Ops.push_back(NewChain);















      NewChain = DAG.getNode(ISD::TokenFactor, LdDL, MVT::Other, Ops);















    }







































llvm/test/CodeGen/X86/pr34088.ll
0 → 100644



+46
−0






























Original line number
Diff line number
Diff line













; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py













; RUN: llc < %s -mtriple=i686-unknown -mcpu=pentium4 | FileCheck %s



























%struct.Foo = type { i32, %struct.Bar }













%struct.Bar = type { i32, %struct.Buffer, i32 }













%struct.Buffer = type { i8*, i32 }



























; This test checks that the load of store %2 is not dropped.













; 













define i32 @pr34088() local_unnamed_addr {













; CHECK-LABEL: pr34088:













; CHECK:       # BB#0: # %entry













; CHECK-NEXT:    pushl %ebp













; CHECK-NEXT:  .Lcfi0:













; CHECK-NEXT:    .cfi_def_cfa_offset 8













; CHECK-NEXT:  .Lcfi1:













; CHECK-NEXT:    .cfi_offset %ebp, -8













; CHECK-NEXT:    movl %esp, %ebp













; CHECK-NEXT:  .Lcfi2:













; CHECK-NEXT:    .cfi_def_cfa_register %ebp













; CHECK-NEXT:    andl $-16, %esp













; CHECK-NEXT:    subl $32, %esp













; CHECK-NEXT:    xorps %xmm0, %xmm0













; CHECK-NEXT:    movaps {{.*#+}} xmm1 = [205,205,205,205,205,205,205,205,205,205,205,205,205,205,205,205]













; CHECK-NEXT:    xorl %eax, %eax













; CHECK-NEXT:    movaps %xmm0, (%esp)













; CHECK-NEXT:    movsd {{.*#+}} xmm0 = mem[0],zero













; CHECK-NEXT:    movaps %xmm1, (%esp)













; CHECK-NEXT:    movl $-842150451, {{[0-9]+}}(%esp) # imm = 0xCDCDCDCD













; CHECK-NEXT:    movsd %xmm0, {{[0-9]+}}(%esp)













; CHECK-NEXT:    movl %ebp, %esp













; CHECK-NEXT:    popl %ebp













; CHECK-NEXT:    retl













entry:













  %foo = alloca %struct.Foo, align 4













  %0 = bitcast %struct.Foo* %foo to i8*













  call void @llvm.memset.p0i8.i32(i8* nonnull %0, i8 0, i32 20, i32 4, i1 false)













  %buffer1 = getelementptr inbounds %struct.Foo, %struct.Foo* %foo, i32 0, i32 1, i32 1













  %1 = bitcast %struct.Buffer* %buffer1 to i64*













  %2 = load i64, i64* %1, align 4













  call void @llvm.memset.p0i8.i32(i8* nonnull %0, i8 -51, i32 20, i32 4, i1 false)













  store i64 %2, i64* %1, align 4













  ret i32 0













}



























declare void @llvm.memset.p0i8.i32(i8* nocapture writeonly, i8, i32, i32, i1)