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[DAG] Prevent Stale nodes from entering worklist 

Add check that deleted nodes do not get added to worklist. This can
occur when a node's operand is simplified to an existing node.

This fixes PR32108.

Reviewers: jyknight, hfinkel, chandlerc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D30506

llvm-svn: 296668
This commit is contained in:
Nirav Dave 2017-03-01 20:19:38 +00:00
parent 3de7fce3ac
commit 0a4703b5ec
2 changed files with 30 additions and 4 deletions
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14
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -129,6 +129,9 @@ namespace {
/// Add to the worklist making sure its instance is at the back (next to be
/// processed.)
void AddToWorklist(SDNode *N) {
assert(N->getOpcode() != ISD::DELETED_NODE &&
"Deleted Node added to Worklist");
// Skip handle nodes as they can't usefully be combined and confuse the
// zero-use deletion strategy.
if (N->getOpcode() == ISD::HANDLENODE)
@ -12619,10 +12622,13 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
Value,
APInt::getLowBitsSet(Value.getScalarValueSizeInBits(),
ST->getMemoryVT().getScalarSizeInBits()))) {
// Re-visit the store if anything changed; SimplifyDemandedBits
// will add Value's node back to the worklist if necessary, but
// we also need to re-visit the Store node itself.
AddToWorklist(N);
// Re-visit the store if anything changed and the store hasn't
// been merged with another node (N is deleted);
// SimplifyDemandedBits will add Value's node back to the
// worklist if necessary, but we also need to re-visit the Store
// node itself.
if (N->getOpcode() != ISD::DELETED_NODE)
AddToWorklist(N);
return SDValue(N, 0);
}
}

20
llvm/test/CodeGen/X86/pr32108.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: llc -march=x86-64 %s -o -
target triple = "x86_64-unknown-linux-gnu"
define void @autogen_SD1794() {
BB:
%Cmp45 = icmp slt <4 x i32> undef, undef
br label %CF243
CF243: ; preds = %CF243, %BB
br i1 undef, label %CF243, label %CF257
CF257: ; preds = %CF243
%Shuff144 = shufflevector <4 x i1> undef, <4 x i1> %Cmp45, <4 x i32> <i32 undef, i32 undef, i32 5, i32 undef>
br label %CF244
CF244: ; preds = %CF244, %CF257
%Shuff182 = shufflevector <4 x i1> %Shuff144, <4 x i1> zeroinitializer, <4 x i32> <i32 3, i32 5, i32 7, i32 undef>
br label %CF244
}