r337275 - [ASTImporter] Fix poisonous structural equivalence cache
Gabor Marton via cfe-commits
cfe-commits at lists.llvm.org
Tue Jul 17 05:39:27 PDT 2018
Author: martong
Date: Tue Jul 17 05:39:27 2018
New Revision: 337275
URL: http://llvm.org/viewvc/llvm-project?rev=337275&view=rev
Log:
[ASTImporter] Fix poisonous structural equivalence cache
Summary:
Implementation functions call into the member functions of
ASTStructuralEquivalence, thus they can falsely alter the DeclsToCheck state
(they add decls). This results that some leaf declarations can be stated as
inequivalent as a side effect of one inequivalent element in the DeclsToCheck
list. And since we store the non-equivalencies, any (otherwise independent)
decls will be rendered as non-equivalent. Solution: I tried to clearly
separate the implementation functions (the static ones) and the public
interface. From now on, the implementation functions do not call any public
member functions, only other implementation functions.
Reviewers: a.sidorin, a_sidorin, r.stahl
Subscribers: rnkovacs, dkrupp, cfe-commits
Differential Revision: https://reviews.llvm.org/D49300
Modified:
cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h
cfe/trunk/lib/AST/ASTImporter.cpp
cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
cfe/trunk/lib/Sema/SemaType.cpp
cfe/trunk/unittests/AST/StructuralEquivalenceTest.cpp
Modified: cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h?rev=337275&r1=337274&r2=337275&view=diff
==============================================================================
--- cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h (original)
+++ cfe/trunk/include/clang/AST/ASTStructuralEquivalence.h Tue Jul 17 05:39:27 2018
@@ -85,10 +85,18 @@ struct StructuralEquivalenceContext {
/// Determine whether the two declarations are structurally
/// equivalent.
- bool IsStructurallyEquivalent(Decl *D1, Decl *D2);
+ /// Implementation functions (all static functions in
+ /// ASTStructuralEquivalence.cpp) must never call this function because that
+ /// will wreak havoc the internal state (\c DeclsToCheck and
+ /// \c TentativeEquivalences members) and can cause faulty equivalent results.
+ bool IsEquivalent(Decl *D1, Decl *D2);
/// Determine whether the two types are structurally equivalent.
- bool IsStructurallyEquivalent(QualType T1, QualType T2);
+ /// Implementation functions (all static functions in
+ /// ASTStructuralEquivalence.cpp) must never call this function because that
+ /// will wreak havoc the internal state (\c DeclsToCheck and
+ /// \c TentativeEquivalences members) and can cause faulty equivalent results.
+ bool IsEquivalent(QualType T1, QualType T2);
/// Find the index of the given anonymous struct/union within its
/// context.
Modified: cfe/trunk/lib/AST/ASTImporter.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ASTImporter.cpp?rev=337275&r1=337274&r2=337275&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ASTImporter.cpp (original)
+++ cfe/trunk/lib/AST/ASTImporter.cpp Tue Jul 17 05:39:27 2018
@@ -295,6 +295,7 @@ namespace clang {
bool ImportTemplateInformation(FunctionDecl *FromFD, FunctionDecl *ToFD);
+ bool IsStructuralMatch(Decl *From, Decl *To, bool Complain);
bool IsStructuralMatch(RecordDecl *FromRecord, RecordDecl *ToRecord,
bool Complain = true);
bool IsStructuralMatch(VarDecl *FromVar, VarDecl *ToVar,
@@ -1592,7 +1593,15 @@ getStructuralEquivalenceKind(const ASTIm
: StructuralEquivalenceKind::Default;
}
-bool ASTNodeImporter::IsStructuralMatch(RecordDecl *FromRecord,
+bool ASTNodeImporter::IsStructuralMatch(Decl *From, Decl *To, bool Complain) {
+ StructuralEquivalenceContext Ctx(
+ Importer.getFromContext(), Importer.getToContext(),
+ Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
+ false, Complain);
+ return Ctx.IsEquivalent(From, To);
+}
+
+bool ASTNodeImporter::IsStructuralMatch(RecordDecl *FromRecord,
RecordDecl *ToRecord, bool Complain) {
// Eliminate a potential failure point where we attempt to re-import
// something we're trying to import while completing ToRecord.
@@ -1608,7 +1617,7 @@ bool ASTNodeImporter::IsStructuralMatch(
Importer.getNonEquivalentDecls(),
getStructuralEquivalenceKind(Importer),
false, Complain);
- return Ctx.IsStructurallyEquivalent(FromRecord, ToRecord);
+ return Ctx.IsEquivalent(FromRecord, ToRecord);
}
bool ASTNodeImporter::IsStructuralMatch(VarDecl *FromVar, VarDecl *ToVar,
@@ -1617,14 +1626,14 @@ bool ASTNodeImporter::IsStructuralMatch(
Importer.getFromContext(), Importer.getToContext(),
Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
false, Complain);
- return Ctx.IsStructurallyEquivalent(FromVar, ToVar);
+ return Ctx.IsEquivalent(FromVar, ToVar);
}
bool ASTNodeImporter::IsStructuralMatch(EnumDecl *FromEnum, EnumDecl *ToEnum) {
StructuralEquivalenceContext Ctx(
Importer.getFromContext(), Importer.getToContext(),
Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer));
- return Ctx.IsStructurallyEquivalent(FromEnum, ToEnum);
+ return Ctx.IsEquivalent(FromEnum, ToEnum);
}
bool ASTNodeImporter::IsStructuralMatch(FunctionTemplateDecl *From,
@@ -1633,7 +1642,7 @@ bool ASTNodeImporter::IsStructuralMatch(
Importer.getFromContext(), Importer.getToContext(),
Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
false, false);
- return Ctx.IsStructurallyEquivalent(From, To);
+ return Ctx.IsEquivalent(From, To);
}
bool ASTNodeImporter::IsStructuralMatch(FunctionDecl *From, FunctionDecl *To) {
@@ -1641,7 +1650,7 @@ bool ASTNodeImporter::IsStructuralMatch(
Importer.getFromContext(), Importer.getToContext(),
Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
false, false);
- return Ctx.IsStructurallyEquivalent(From, To);
+ return Ctx.IsEquivalent(From, To);
}
bool ASTNodeImporter::IsStructuralMatch(EnumConstantDecl *FromEC,
@@ -1660,7 +1669,7 @@ bool ASTNodeImporter::IsStructuralMatch(
Importer.getToContext(),
Importer.getNonEquivalentDecls(),
getStructuralEquivalenceKind(Importer));
- return Ctx.IsStructurallyEquivalent(From, To);
+ return Ctx.IsEquivalent(From, To);
}
bool ASTNodeImporter::IsStructuralMatch(VarTemplateDecl *From,
@@ -1669,7 +1678,7 @@ bool ASTNodeImporter::IsStructuralMatch(
Importer.getToContext(),
Importer.getNonEquivalentDecls(),
getStructuralEquivalenceKind(Importer));
- return Ctx.IsStructurallyEquivalent(From, To);
+ return Ctx.IsEquivalent(From, To);
}
Decl *ASTNodeImporter::VisitDecl(Decl *D) {
@@ -2978,15 +2987,11 @@ Decl *ASTNodeImporter::VisitFriendDecl(F
// FriendDecl is not a NamedDecl so we cannot use localUncachedLookup.
auto *RD = cast<CXXRecordDecl>(DC);
FriendDecl *ImportedFriend = RD->getFirstFriend();
- StructuralEquivalenceContext Context(
- Importer.getFromContext(), Importer.getToContext(),
- Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
- false, false);
while (ImportedFriend) {
if (D->getFriendDecl() && ImportedFriend->getFriendDecl()) {
- if (Context.IsStructurallyEquivalent(D->getFriendDecl(),
- ImportedFriend->getFriendDecl()))
+ if (IsStructuralMatch(D->getFriendDecl(), ImportedFriend->getFriendDecl(),
+ /*Complain=*/false))
return Importer.MapImported(D, ImportedFriend);
} else if (D->getFriendType() && ImportedFriend->getFriendType()) {
@@ -7621,5 +7626,5 @@ bool ASTImporter::IsStructurallyEquivale
StructuralEquivalenceContext Ctx(FromContext, ToContext, NonEquivalentDecls,
getStructuralEquivalenceKind(*this), false,
Complain);
- return Ctx.IsStructurallyEquivalent(From, To);
+ return Ctx.IsEquivalent(From, To);
}
Modified: cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp?rev=337275&r1=337274&r2=337275&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp (original)
+++ cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp Tue Jul 17 05:39:27 2018
@@ -10,6 +10,59 @@
// This file implement StructuralEquivalenceContext class and helper functions
// for layout matching.
//
+// The structural equivalence check could have been implemented as a parallel
+// BFS on a pair of graphs. That must have been the original approach at the
+// beginning.
+// Let's consider this simple BFS algorithm from the `s` source:
+// ```
+// void bfs(Graph G, int s)
+// {
+// Queue<Integer> queue = new Queue<Integer>();
+// marked[s] = true; // Mark the source
+// queue.enqueue(s); // and put it on the queue.
+// while (!q.isEmpty()) {
+// int v = queue.dequeue(); // Remove next vertex from the queue.
+// for (int w : G.adj(v))
+// if (!marked[w]) // For every unmarked adjacent vertex,
+// {
+// marked[w] = true;
+// queue.enqueue(w);
+// }
+// }
+// }
+// ```
+// Indeed, it has it's queue, which holds pairs of nodes, one from each graph,
+// this is the `DeclsToCheck` and it's pair is in `TentativeEquivalences`.
+// `TentativeEquivalences` also plays the role of the marking (`marked`)
+// functionality above, we use it to check whether we've already seen a pair of
+// nodes.
+//
+// We put in the elements into the queue only in the toplevel decl check
+// function:
+// ```
+// static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+// Decl *D1, Decl *D2);
+// ```
+// The `while` loop where we iterate over the children is implemented in
+// `Finish()`. And `Finish` is called only from the two **member** functions
+// which check the equivalency of two Decls or two Types. ASTImporter (and
+// other clients) call only these functions.
+//
+// The `static` implementation functions are called from `Finish`, these push
+// the children nodes to the queue via `static bool
+// IsStructurallyEquivalent(StructuralEquivalenceContext &Context, Decl *D1,
+// Decl *D2)`. So far so good, this is almost like the BFS. However, if we
+// let a static implementation function to call `Finish` via another **member**
+// function that means we end up with two nested while loops each of them
+// working on the same queue. This is wrong and nobody can reason about it's
+// doing. Thus, static implementation functions must not call the **member**
+// functions.
+//
+// So, now `TentativeEquivalences` plays two roles. It is used to store the
+// second half of the decls which we want to compare, plus it plays a role in
+// closing the recursion. On a long term, we could refactor structural
+// equivalency to be more alike to the traditional BFS.
+//
//===----------------------------------------------------------------------===//
#include "clang/AST/ASTStructuralEquivalence.h"
@@ -184,10 +237,10 @@ static bool IsStructurallyEquivalent(Str
return true;
case TemplateArgument::Type:
- return Context.IsStructurallyEquivalent(Arg1.getAsType(), Arg2.getAsType());
+ return IsStructurallyEquivalent(Context, Arg1.getAsType(), Arg2.getAsType());
case TemplateArgument::Integral:
- if (!Context.IsStructurallyEquivalent(Arg1.getIntegralType(),
+ if (!IsStructurallyEquivalent(Context, Arg1.getIntegralType(),
Arg2.getIntegralType()))
return false;
@@ -195,7 +248,7 @@ static bool IsStructurallyEquivalent(Str
Arg2.getAsIntegral());
case TemplateArgument::Declaration:
- return Context.IsStructurallyEquivalent(Arg1.getAsDecl(), Arg2.getAsDecl());
+ return IsStructurallyEquivalent(Context, Arg1.getAsDecl(), Arg2.getAsDecl());
case TemplateArgument::NullPtr:
return true; // FIXME: Is this correct?
@@ -1205,8 +1258,8 @@ static bool IsStructurallyEquivalent(Str
return false;
}
- if (!Context.IsStructurallyEquivalent(Params1->getParam(I),
- Params2->getParam(I)))
+ if (!IsStructurallyEquivalent(Context, Params1->getParam(I),
+ Params2->getParam(I)))
return false;
}
@@ -1243,7 +1296,7 @@ static bool IsStructurallyEquivalent(Str
}
// Check types.
- if (!Context.IsStructurallyEquivalent(D1->getType(), D2->getType())) {
+ if (!IsStructurallyEquivalent(Context, D1->getType(), D2->getType())) {
if (Context.Complain) {
Context.Diag2(D2->getLocation(),
diag::err_odr_non_type_parameter_type_inconsistent)
@@ -1294,8 +1347,8 @@ static bool IsStructurallyEquivalent(Str
return false;
// Check the templated declaration.
- return Context.IsStructurallyEquivalent(D1->getTemplatedDecl(),
- D2->getTemplatedDecl());
+ return IsStructurallyEquivalent(Context, D1->getTemplatedDecl(),
+ D2->getTemplatedDecl());
}
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
@@ -1306,8 +1359,8 @@ static bool IsStructurallyEquivalent(Str
return false;
// Check the templated declaration.
- return Context.IsStructurallyEquivalent(D1->getTemplatedDecl()->getType(),
- D2->getTemplatedDecl()->getType());
+ return IsStructurallyEquivalent(Context, D1->getTemplatedDecl()->getType(),
+ D2->getTemplatedDecl()->getType());
}
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
@@ -1418,16 +1471,26 @@ StructuralEquivalenceContext::findUntagg
return Index;
}
-bool StructuralEquivalenceContext::IsStructurallyEquivalent(Decl *D1,
- Decl *D2) {
+bool StructuralEquivalenceContext::IsEquivalent(Decl *D1, Decl *D2) {
+
+ // Ensure that the implementation functions (all static functions in this TU)
+ // never call the public ASTStructuralEquivalence::IsEquivalent() functions,
+ // because that will wreak havoc the internal state (DeclsToCheck and
+ // TentativeEquivalences members) and can cause faulty behaviour. For
+ // instance, some leaf declarations can be stated and cached as inequivalent
+ // as a side effect of one inequivalent element in the DeclsToCheck list.
+ assert(DeclsToCheck.empty());
+ assert(TentativeEquivalences.empty());
+
if (!::IsStructurallyEquivalent(*this, D1, D2))
return false;
return !Finish();
}
-bool StructuralEquivalenceContext::IsStructurallyEquivalent(QualType T1,
- QualType T2) {
+bool StructuralEquivalenceContext::IsEquivalent(QualType T1, QualType T2) {
+ assert(DeclsToCheck.empty());
+ assert(TentativeEquivalences.empty());
if (!::IsStructurallyEquivalent(*this, T1, T2))
return false;
Modified: cfe/trunk/lib/Sema/SemaType.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaType.cpp?rev=337275&r1=337274&r2=337275&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaType.cpp (original)
+++ cfe/trunk/lib/Sema/SemaType.cpp Tue Jul 17 05:39:27 2018
@@ -7498,7 +7498,7 @@ bool Sema::hasStructuralCompatLayout(Dec
StructuralEquivalenceKind::Default,
false /*StrictTypeSpelling*/, true /*Complain*/,
true /*ErrorOnTagTypeMismatch*/);
- return Ctx.IsStructurallyEquivalent(D, Suggested);
+ return Ctx.IsEquivalent(D, Suggested);
}
/// Determine whether there is any declaration of \p D that was ever a
Modified: cfe/trunk/unittests/AST/StructuralEquivalenceTest.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/unittests/AST/StructuralEquivalenceTest.cpp?rev=337275&r1=337274&r2=337275&view=diff
==============================================================================
--- cfe/trunk/unittests/AST/StructuralEquivalenceTest.cpp (original)
+++ cfe/trunk/unittests/AST/StructuralEquivalenceTest.cpp Tue Jul 17 05:39:27 2018
@@ -82,7 +82,7 @@ struct StructuralEquivalenceTest : ::tes
StructuralEquivalenceContext Ctx(
D0->getASTContext(), D1->getASTContext(), NonEquivalentDecls,
StructuralEquivalenceKind::Default, false, false);
- return Ctx.IsStructurallyEquivalent(D0, D1);
+ return Ctx.IsEquivalent(D0, D1);
}
bool testStructuralMatch(std::tuple<Decl *, Decl *> t) {
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