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LowerBitSets: Fix non-determinism bug.

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Visit disjoint sets in a deterministic order based on the maximum BitSetNM
index, otherwise the order in which we visit them will depend on pointer
comparisons. This was being exposed by MSan.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247201 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne 2015-09-09 22:30:32 +00:00
parent 69d051c87d
commit d77a329d71
3 changed files with 30 additions and 12 deletions
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26
lib/Transforms/IPO/LowerBitSets.cpp
View File

@ -938,7 +938,7 @@ bool LowerBitSets::buildBitSets() {
for (unsigned I = 0, E = BitSetNM->getNumOperands(); I != E; ++I) {
MDNode *Op = BitSetNM->getOperand(I);
verifyBitSetMDNode(Op);
BitSetIdIndices[Op] = I;
BitSetIdIndices[Op->getOperand(0)] = I;
}
}
@ -988,18 +988,36 @@ bool LowerBitSets::buildBitSets() {
if (GlobalClasses.empty())
return false;
// For each disjoint set we found...
// Build a list of disjoint sets ordered by their maximum BitSetNM index
// for determinism.
std::vector<std::pair<GlobalClassesTy::iterator, unsigned>> Sets;
for (GlobalClassesTy::iterator I = GlobalClasses.begin(),
E = GlobalClasses.end();
I != E; ++I) {
if (!I->isLeader()) continue;
++NumBitSetDisjointSets;
unsigned MaxIndex = 0;
for (GlobalClassesTy::member_iterator MI = GlobalClasses.member_begin(I);
MI != GlobalClasses.member_end(); ++MI) {
if ((*MI).is<Metadata *>())
MaxIndex = std::max(MaxIndex, BitSetIdIndices[MI->get<Metadata *>()]);
}
Sets.emplace_back(I, MaxIndex);
}
std::sort(Sets.begin(), Sets.end(),
[](const std::pair<GlobalClassesTy::iterator, unsigned> &S1,
const std::pair<GlobalClassesTy::iterator, unsigned> &S2) {
return S1.second < S2.second;
});
// For each disjoint set we found...
for (const auto &S : Sets) {
// Build the list of bitsets in this disjoint set.
std::vector<Metadata *> BitSets;
std::vector<GlobalObject *> Globals;
for (GlobalClassesTy::member_iterator MI = GlobalClasses.member_begin(I);
for (GlobalClassesTy::member_iterator MI =
GlobalClasses.member_begin(S.first);
MI != GlobalClasses.member_end(); ++MI) {
if ((*MI).is<Metadata *>())
BitSets.push_back(MI->get<Metadata *>());

2
test/Transforms/LowerBitSets/nonstring.ll
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@ -4,8 +4,8 @@
target datalayout = "e-p:32:32"
; CHECK: @[[BNAME:.*]] = private constant { [2 x i32] }
; CHECK: @[[ANAME:.*]] = private constant { i32 }
; CHECK: @[[BNAME:.*]] = private constant { [2 x i32] }
@a = constant i32 1
@b = constant [2 x i32] [i32 2, i32 3]

14
test/Transforms/LowerBitSets/simple.ll
View File

@ -26,15 +26,15 @@ target datalayout = "e-p:32:32"
!4 = !{!"bitset2", i32* @c, i32 0}
; CHECK-NODISCARD-DAG: !{!"bitset2", i32* @c, i32 0}
; Offset 0, 4 byte alignment
!5 = !{!"bitset3", i32* @a, i32 0}
; CHECK-NODISCARD-DAG: !{!"bitset3", i32* @a, i32 0}
!6 = !{!"bitset3", i32* @c, i32 0}
; CHECK-NODISCARD-DAG: !{!"bitset3", i32* @c, i32 0}
; Entries whose second operand is null (the result of a global being DCE'd)
; should be ignored.
!7 = !{!"bitset2", null, i32 0}
!5 = !{!"bitset2", null, i32 0}
; Offset 0, 4 byte alignment
!6 = !{!"bitset3", i32* @a, i32 0}
; CHECK-NODISCARD-DAG: !{!"bitset3", i32* @a, i32 0}
!7 = !{!"bitset3", i32* @c, i32 0}
; CHECK-NODISCARD-DAG: !{!"bitset3", i32* @c, i32 0}
!llvm.bitsets = !{ !0, !1, !2, !3, !4, !5, !6, !7 }