From 206a357684ec4f9159905eb7293bfb2221af0e14 Mon Sep 17 00:00:00 2001 From: Nate Begeman Date: Wed, 16 Sep 2009 03:20:46 +0000 Subject: [PATCH] Do not try and sink a load whose chain result has more than one use, when trying to create RMW opportunities in the x86 backend. This can cause a cycle to appear in the graph, since the other uses may eventually feed into the TokenFactor we are sinking the load below. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81996 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/X86/X86ISelDAGToDAG.cpp | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp index a900a69ba71..21681f9c4d0 100644 --- a/lib/Target/X86/X86ISelDAGToDAG.cpp +++ b/lib/Target/X86/X86ISelDAGToDAG.cpp @@ -364,7 +364,9 @@ static void MoveBelowTokenFactor(SelectionDAG *CurDAG, SDValue Load, Store.getOperand(2), Store.getOperand(3)); } -/// isRMWLoad - Return true if N is a load that's part of RMW sub-DAG. +/// isRMWLoad - Return true if N is a load that's part of RMW sub-DAG. The +/// chain produced by the load must only be used by the store's chain operand, +/// otherwise this may produce a cycle in the DAG. /// static bool isRMWLoad(SDValue N, SDValue Chain, SDValue Address, SDValue &Load) { @@ -382,8 +384,9 @@ static bool isRMWLoad(SDValue N, SDValue Chain, SDValue Address, return false; if (N.hasOneUse() && + LD->hasNUsesOfValue(1, 1) && N.getOperand(1) == Address && - N.getNode()->isOperandOf(Chain.getNode())) { + LD->isOperandOf(Chain.getNode())) { Load = N; return true; } -- 2.34.1