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[Dominators] Visit affected node candidates found at different root levels

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Summary:
This patch attempts to fix the DomTree incremental insertion bug found here [[ https://bugs.llvm.org/show_bug.cgi?id=35969 | PR35969 ]] .

When performing an insertion into a piece of unreachable CFG, we may find the same not at different levels. When this happens, the node can turn out to be affected when we find it starting from a node with a lower level in the tree. The level at which we start visitation affects if we consider a node affected or not.

This patch tracks the lowest level at which each node was visited during insertion and allows it to be visited multiple times, if it can cause it to be considered affected.

Reviewers: brzycki, davide, dberlin, grosser

Reviewed By: brzycki

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D42231

llvm-svn: 322993
This commit is contained in:
Jakub Kuderski 2018-01-19 21:27:24 +00:00
parent 2a4afe839c
commit ff611e1c1f
4 changed files with 172 additions and 9 deletions
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38
include/llvm/Support/GenericDomTreeConstruction.h
View File

@ -628,7 +628,7 @@ struct SemiNCAInfo {
DecreasingLevel>
Bucket; // Queue of tree nodes sorted by level in descending order.
SmallDenseSet<TreeNodePtr, 8> Affected;
SmallDenseSet<TreeNodePtr, 8> Visited;
SmallDenseMap<TreeNodePtr, unsigned, 8> Visited;
SmallVector<TreeNodePtr, 8> AffectedQueue;
SmallVector<TreeNodePtr, 8> VisitedNotAffectedQueue;
};
@ -753,14 +753,16 @@ struct SemiNCAInfo {
while (!II.Bucket.empty()) {
const TreeNodePtr CurrentNode = II.Bucket.top().second;
const unsigned CurrentLevel = CurrentNode->getLevel();
II.Bucket.pop();
DEBUG(dbgs() << "\tAdding to Visited and AffectedQueue: "
<< BlockNamePrinter(CurrentNode) << "\n");
II.Visited.insert(CurrentNode);
II.Visited.insert({CurrentNode, CurrentLevel});
II.AffectedQueue.push_back(CurrentNode);
// Discover and collect affected successors of the current node.
VisitInsertion(DT, BUI, CurrentNode, CurrentNode->getLevel(), NCD, II);
VisitInsertion(DT, BUI, CurrentNode, CurrentLevel, NCD, II);
}
// Finish by updating immediate dominators and levels.
@ -772,13 +774,17 @@ struct SemiNCAInfo {
const TreeNodePtr TN, const unsigned RootLevel,
const TreeNodePtr NCD, InsertionInfo &II) {
const unsigned NCDLevel = NCD->getLevel();
DEBUG(dbgs() << "Visiting " << BlockNamePrinter(TN) << "\n");
DEBUG(dbgs() << "Visiting " << BlockNamePrinter(TN) << ", RootLevel "
<< RootLevel << "\n");
SmallVector<TreeNodePtr, 8> Stack = {TN};
assert(TN->getBlock() && II.Visited.count(TN) && "Preconditions!");
SmallPtrSet<TreeNodePtr, 8> Processed;
do {
TreeNodePtr Next = Stack.pop_back_val();
DEBUG(dbgs() << " Next: " << BlockNamePrinter(Next) << "\n");
for (const NodePtr Succ :
ChildrenGetter<IsPostDom>::Get(Next->getBlock(), BUI)) {
@ -786,19 +792,31 @@ struct SemiNCAInfo {
assert(SuccTN && "Unreachable successor found at reachable insertion");
const unsigned SuccLevel = SuccTN->getLevel();
DEBUG(dbgs() << "\tSuccessor " << BlockNamePrinter(Succ)
<< ", level = " << SuccLevel << "\n");
DEBUG(dbgs() << "\tSuccessor " << BlockNamePrinter(Succ) << ", level = "
<< SuccLevel << "\n");
// Do not process the same node multiple times.
if (Processed.count(Next) > 0)
continue;
// Succ dominated by subtree From -- not affected.
// (Based on the lemma 2.5 from the second paper.)
if (SuccLevel > RootLevel) {
DEBUG(dbgs() << "\t\tDominated by subtree From\n");
if (II.Visited.count(SuccTN) != 0)
continue;
if (II.Visited.count(SuccTN) != 0) {
DEBUG(dbgs() << "\t\t\talready visited at level "
<< II.Visited[SuccTN] << "\n\t\t\tcurrent level "
<< RootLevel << ")\n");
// A node can be necessary to visit again if we see it again at
// a lower level than before.
if (II.Visited[SuccTN] >= RootLevel)
continue;
}
DEBUG(dbgs() << "\t\tMarking visited not affected "
<< BlockNamePrinter(Succ) << "\n");
II.Visited.insert(SuccTN);
II.Visited.insert({SuccTN, RootLevel});
II.VisitedNotAffectedQueue.push_back(SuccTN);
Stack.push_back(SuccTN);
} else if ((SuccLevel > NCDLevel + 1) &&
@ -809,6 +827,8 @@ struct SemiNCAInfo {
II.Bucket.push({SuccLevel, SuccTN});
}
}
Processed.insert(Next);
} while (!Stack.empty());
}

43
test/Transforms/JumpThreading/ddt-crash3.ll Normal file
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@ -0,0 +1,43 @@
; RUN: opt < %s -jump-threading -disable-output -verify-dom-info
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@global = external local_unnamed_addr global i64, align 8
@global.1 = external local_unnamed_addr global i64, align 8
@global.2 = external local_unnamed_addr global i64, align 8
; Function Attrs: norecurse noreturn nounwind uwtable
define void @hoge() local_unnamed_addr #0 {
bb:
br label %bb1
bb1: ; preds = %bb26, %bb
%tmp = load i64, i64* @global, align 8, !tbaa !1
%tmp2 = icmp eq i64 %tmp, 0
br i1 %tmp2, label %bb27, label %bb3
bb3: ; preds = %bb1
%tmp4 = load i64, i64* @global.1, align 8, !tbaa !1
%tmp5 = icmp eq i64 %tmp4, 0
br i1 %tmp5, label %bb23, label %bb23
bb23: ; preds = %bb3, %bb3
br label %bb26
bb26: ; preds = %bb27, %bb23
br label %bb1
bb27: ; preds = %bb1
br label %bb26
}
attributes #0 = { norecurse noreturn nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.ident = !{!0}
!0 = !{!"clang version 7.0.0 "}
!1 = !{!2, !2, i64 0}
!2 = !{!"long", !3, i64 0}
!3 = !{!"omnipotent char", !4, i64 0}
!4 = !{!"Simple C/C++ TBAA"}

75
test/Transforms/JumpThreading/ddt-crash4.ll Normal file
View File

@ -0,0 +1,75 @@
; RUN: opt < %s -jump-threading -disable-output -verify-dom-info
@global = external global i64, align 8
define void @f() {
bb:
br label %bb1
bb1:
%tmp = load i64, i64* @global, align 8
%tmp2 = icmp eq i64 %tmp, 0
br i1 %tmp2, label %bb27, label %bb3
bb3:
%tmp4 = load i64, i64* @global, align 8
%tmp5 = icmp eq i64 %tmp4, 0
br i1 %tmp5, label %bb6, label %bb7
bb6:
br label %bb7
bb7:
%tmp8 = phi i1 [ true, %bb3 ], [ undef, %bb6 ]
%tmp9 = select i1 %tmp8, i64 %tmp4, i64 0
br i1 false, label %bb10, label %bb23
bb10:
%tmp11 = load i64, i64* @global, align 8
%tmp12 = icmp slt i64 %tmp11, 5
br i1 %tmp12, label %bb13, label %bb17
bb13:
br label %bb14
bb14:
br i1 undef, label %bb15, label %bb16
bb15:
unreachable
bb16:
br label %bb10
bb17:
br label %bb18
bb18:
br i1 undef, label %bb22, label %bb13
bb19:
br i1 undef, label %bb20, label %bb21
bb20:
unreachable
bb21:
br label %bb18
bb22:
br label %bb23
bb23:
br i1 undef, label %bb24, label %bb13
bb24:
br i1 undef, label %bb26, label %bb25
bb25:
br label %bb19
bb26:
br label %bb1
bb27:
br label %bb24
}

25
unittests/IR/DominatorTreeTest.cpp
View File

@ -925,3 +925,28 @@ TEST(DominatorTree, InsertDeleteExhaustive) {
}
}
}
TEST(DominatorTree, InsertIntoIrreducible) {
std::vector<CFGBuilder::Arc> Arcs = {
{"0", "1"},
{"1", "27"}, {"1", "7"},
{"10", "18"},
{"13", "10"},
{"18", "13"}, {"18", "23"},
{"23", "13"}, {"23", "24"},
{"24", "1"}, {"24", "18"},
{"27", "24"}};
CFGHolder Holder;
CFGBuilder B(Holder.F, Arcs, {{Insert, {"7", "23"}}});
DominatorTree DT(*Holder.F);
EXPECT_TRUE(DT.verify());
B.applyUpdate();
BasicBlock *From = B.getOrAddBlock("7");
BasicBlock *To = B.getOrAddBlock("23");
DT.insertEdge(From, To);
EXPECT_TRUE(DT.verify());
}