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
diff --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h
index 55a23c3..d6851f7 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAG.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -1220,8 +1220,9 @@
/// 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
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 823e778..0ff1547 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -7262,22 +7262,23 @@
AddDbgValue(I, ToNode, false);
}
-void SelectionDAG::makeEquivalentMemoryOrdering(LoadSDNode *OldLoad,
- SDValue NewMemOp) {
+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;
}
//===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index ced551b..a4770e7 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -33386,7 +33386,8 @@
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 @@
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);
}
diff --git a/llvm/test/CodeGen/X86/pr34088.ll b/llvm/test/CodeGen/X86/pr34088.ll
new file mode 100644
index 0000000..d3667e3
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pr34088.ll
@@ -0,0 +1,46 @@
+; 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)
