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[MemProf] Avoid duplicate edges between nodes (#113337)
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The recent change to add support for cloning indirect calls
inadvertantly caused duplicate edges to be created between the same
caller/callee pair. This is due to the new moveCalleeEdgeToNewCaller
not properly guarding the addition of a new edge (ironically I was
testing for that in an assertion, but failed to handle that case
specially otherwise). Now simply move the context ids over to any
existing edge.

This issue in turn led to some assumptions in cloning being violated,
resulting in a later crash.

Add a test for this case to checkNode.
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@teresajohnson
teresajohnson authored Oct 25, 2024
1 parent 843c2fb commit 144ddca
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Showing 2 changed files with 48 additions and 7 deletions.
21 changes: 20 additions & 1 deletion llvm/lib/Transforms/IPO/MemProfContextDisambiguation.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1352,6 +1352,17 @@ static void checkNode(const ContextNode<DerivedCCG, FuncTy, CallTy> *Node,
}
assert(NodeContextIds == CalleeEdgeContextIds);
}
// FIXME: Since this checking is only invoked under an option, we should
// change the error checking from using assert to something that will trigger
// an error on a release build.
#ifndef NDEBUG
// Make sure we don't end up with duplicate edges between the same caller and
// callee.
DenseSet<ContextNode<DerivedCCG, FuncTy, CallTy> *> NodeSet;
for (const auto &E : Node->CalleeEdges)
NodeSet.insert(E->Callee);
assert(NodeSet.size() == Node->CalleeEdges.size());
#endif
}

template <typename DerivedCCG, typename FuncTy, typename CallTy>
Expand Down Expand Up @@ -3125,7 +3136,15 @@ void CallsiteContextGraph<DerivedCCG, FuncTy, CallTy>::
// from the same callers as the old node. That should be true in the current
// use case, where we will remove None-type edges after copying over all
// caller edges from the callee.
assert(IsNewNode || NewCaller->findEdgeFromCaller(OldCallerEdge->Caller));
auto *ExistingCallerEdge =
NewCaller->findEdgeFromCaller(OldCallerEdge->Caller);
assert(IsNewNode || ExistingCallerEdge);
if (ExistingCallerEdge) {
ExistingCallerEdge->getContextIds().insert(EdgeContextIdsToMove.begin(),
EdgeContextIdsToMove.end());
ExistingCallerEdge->AllocTypes |= computeAllocType(EdgeContextIdsToMove);
continue;
}
auto NewEdge = std::make_shared<ContextEdge>(
NewCaller, OldCallerEdge->Caller,
computeAllocType(EdgeContextIdsToMove), EdgeContextIdsToMove);
Expand Down
34 changes: 28 additions & 6 deletions llvm/test/ThinLTO/X86/memprof-icp.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -186,9 +186,13 @@
; REMARKS-MAIN: created clone _ZN2B03barEj.memprof.1
; REMARKS-MAIN: call in clone _ZN2B03barEj marked with memprof allocation attribute notcold
; REMARKS-MAIN: call in clone _ZN2B03barEj.memprof.1 marked with memprof allocation attribute cold
; REMARKS-MAIN: call in clone _ZN2B03barEj marked with memprof allocation attribute notcold
; REMARKS-MAIN: call in clone _ZN2B03barEj.memprof.1 marked with memprof allocation attribute cold
; REMARKS-MAIN: created clone _ZN1B3barEj.memprof.1
; REMARKS-MAIN: call in clone _ZN1B3barEj marked with memprof allocation attribute notcold
; REMARKS-MAIN: call in clone _ZN1B3barEj.memprof.1 marked with memprof allocation attribute cold
; REMARKS-MAIN: call in clone _ZN1B3barEj marked with memprof allocation attribute notcold
; REMARKS-MAIN: call in clone _ZN1B3barEj.memprof.1 marked with memprof allocation attribute cold
; REMARKS-FOO: created clone _Z3fooR2B0j.memprof.1
;; In each version of foo we should have promoted the indirect call to two conditional
;; direct calls, one to B::bar and one to B0::bar. The cloned version of foo should call
Expand All @@ -208,10 +212,10 @@
; REMARKS-FOO: call in clone _ZN1B3barEj marked with memprof allocation attribute notcold
; REMARKS-FOO: call in clone _ZN1B3barEj.memprof.1 marked with memprof allocation attribute cold

; STATS: 2 memprof-context-disambiguation - Number of cold static allocations (possibly cloned) during whole program analysis
; STATS-BE: 4 memprof-context-disambiguation - Number of cold static allocations (possibly cloned) during ThinLTO backend
; STATS: 2 memprof-context-disambiguation - Number of not cold static allocations (possibly cloned) during whole program analysis
; STATS-BE: 4 memprof-context-disambiguation - Number of not cold static allocations (possibly cloned) during ThinLTO backend
; STATS: 4 memprof-context-disambiguation - Number of cold static allocations (possibly cloned) during whole program analysis
; STATS-BE: 8 memprof-context-disambiguation - Number of cold static allocations (possibly cloned) during ThinLTO backend
; STATS: 4 memprof-context-disambiguation - Number of not cold static allocations (possibly cloned) during whole program analysis
; STATS-BE: 8 memprof-context-disambiguation - Number of not cold static allocations (possibly cloned) during ThinLTO backend
; STATS: 3 memprof-context-disambiguation - Number of function clones created during whole program analysis
; STATS-BE: 5 memprof-context-disambiguation - Number of function clones created during ThinLTO backend

Expand Down Expand Up @@ -247,8 +251,8 @@
; IR: attributes #[[NOTCOLD]] = {{.*}} "memprof"="notcold"
; IR: attributes #[[COLD]] = {{.*}} "memprof"="cold"

; STATS-BE-DISTRIB: 2 memprof-context-disambiguation - Number of cold static allocations (possibly cloned) during ThinLTO backend
; STATS-BE-DISTRIB: 2 memprof-context-disambiguation - Number of not cold static allocations (possibly cloned) during ThinLTO backend
; STATS-BE-DISTRIB: 4 memprof-context-disambiguation - Number of cold static allocations (possibly cloned) during ThinLTO backend
; STATS-BE-DISTRIB: 4 memprof-context-disambiguation - Number of not cold static allocations (possibly cloned) during ThinLTO backend
; STATS-BE-DISTRIB: 3 memprof-context-disambiguation - Number of function clones created during ThinLTO backend

;--- foo.ll
Expand Down Expand Up @@ -298,6 +302,9 @@ declare i32 @_Z3fooR2B0j(ptr, i32)
define i32 @_ZN2B03barEj(ptr %this, i32 %s) {
entry:
%call = tail call ptr @_Znwm(i64 noundef 4) #0, !memprof !33, !callsite !38
;; Second allocation in this function, to ensure that indirect edges to the
;; same callee are partitioned correctly.
%call2 = tail call ptr @_Znwm(i64 noundef 4) #0, !memprof !45, !callsite !50
store volatile i32 0, ptr %call, align 4
ret i32 0
}
Expand All @@ -311,6 +318,9 @@ declare void @_ZdlPvm()
define i32 @_ZN1B3barEj(ptr %this, i32 %s) {
entry:
%call = tail call ptr @_Znwm(i64 noundef 4) #0, !memprof !39, !callsite !44
;; Second allocation in this function, to ensure that indirect edges to the
;; same callee are partitioned correctly.
%call2 = tail call ptr @_Znwm(i64 noundef 4) #0, !memprof !51, !callsite !56
store volatile i32 0, ptr %call, align 4
ret i32 0
}
Expand Down Expand Up @@ -367,3 +377,15 @@ attributes #0 = { builtin allocsize(0) }
!42 = !{!43, !"cold"}
!43 = !{i64 4457553070050523782, i64 -2101080423462424381, i64 -6490791336773930154}
!44 = !{i64 4457553070050523782}
!45 = !{!46, !48}
!46 = !{!47, !"notcold"}
!47 = !{i64 456, i64 -2101080423462424381, i64 5188446645037944434}
!48 = !{!49, !"cold"}
!49 = !{i64 456, i64 -2101080423462424381, i64 5583420417449503557}
!50 = !{i64 456}
!51 = !{!52, !54}
!52 = !{!53, !"notcold"}
!53 = !{i64 789, i64 -2101080423462424381, i64 132626519179914298}
!54 = !{!55, !"cold"}
!55 = !{i64 789, i64 -2101080423462424381, i64 -6490791336773930154}
!56 = !{i64 789}

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