[ASTImporter] Add support for importing ChooseExpr AST nodes.

Summary:
This allows ASTs to be merged when they contain ChooseExpr (the GNU
__builtin_choose_expr construction). This is needed, for example, for
cross-CTU analysis of C code that makes use of __builtin_choose_expr.

The node is already supported in the AST, but it didn't have a matcher
in ASTMatchers. So, this change adds the matcher and adds support to
ASTImporter.

Reviewers: shafik, a_sidorin, martong, aaron.ballman

Subscribers: aaron.ballman, rnkovacs, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58292

llvm-svn: 354832

clang/docs/LibASTMatchersReference.html

@@ -788,6 +788,11 @@ Example matches 'a', L'a'
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Stmt.html">Stmt</a>&gt;</td><td class="name" onclick="toggle('chooseExpr0')"><a name="chooseExpr0Anchor">chooseExpr</a></td><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1ChooseExpr.html">ChooseExpr</a>&gt;...</td></tr>
+<tr><td colspan="4" class="doc" id="chooseExpr0"><pre>Matches GNU __builtin_choose_expr.
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Stmt.html">Stmt</a>&gt;</td><td class="name" onclick="toggle('compoundLiteralExpr0')"><a name="compoundLiteralExpr0Anchor">compoundLiteralExpr</a></td><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1CompoundLiteralExpr.html">CompoundLiteralExpr</a>&gt;...</td></tr>
 <tr><td colspan="4" class="doc" id="compoundLiteralExpr0"><pre>Matches compound (i.e. non-scalar) literals
 

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -2158,6 +2158,10 @@ extern const internal::VariadicDynCastAllOfMatcher<Stmt, CompoundLiteralExpr>
 extern const internal::VariadicDynCastAllOfMatcher<Stmt, CXXNullPtrLiteralExpr>
     cxxNullPtrLiteralExpr;
 
+/// Matches GNU __builtin_choose_expr.
+extern const internal::VariadicDynCastAllOfMatcher<Stmt, ChooseExpr>
+    chooseExpr;
+
 /// Matches GNU __null expression.
 extern const internal::VariadicDynCastAllOfMatcher<Stmt, GNUNullExpr>
     gnuNullExpr;

clang/lib/AST/ASTImporter.cpp

@@ -552,6 +552,7 @@ namespace clang {
     // Importing expressions
     ExpectedStmt VisitExpr(Expr *E);
     ExpectedStmt VisitVAArgExpr(VAArgExpr *E);
+    ExpectedStmt VisitChooseExpr(ChooseExpr *E);
     ExpectedStmt VisitGNUNullExpr(GNUNullExpr *E);
     ExpectedStmt VisitPredefinedExpr(PredefinedExpr *E);
     ExpectedStmt VisitDeclRefExpr(DeclRefExpr *E);
@@ -6135,6 +6136,33 @@ ExpectedStmt ASTNodeImporter::VisitVAArgExpr(VAArgExpr *E) {
       E->isMicrosoftABI());
 }
 
+ExpectedStmt ASTNodeImporter::VisitChooseExpr(ChooseExpr *E) {
+  auto Imp = importSeq(E->getCond(), E->getLHS(), E->getRHS(),
+                       E->getBuiltinLoc(), E->getRParenLoc(), E->getType());
+  if (!Imp)
+    return Imp.takeError();
+
+  Expr *ToCond;
+  Expr *ToLHS;
+  Expr *ToRHS;
+  SourceLocation ToBuiltinLoc, ToRParenLoc;
+  QualType ToType;
+  std::tie(ToCond, ToLHS, ToRHS, ToBuiltinLoc, ToRParenLoc, ToType) = *Imp;
+
+  ExprValueKind VK = E->getValueKind();
+  ExprObjectKind OK = E->getObjectKind();
+
+  bool TypeDependent = ToCond->isTypeDependent();
+  bool ValueDependent = ToCond->isValueDependent();
+
+  // The value of CondIsTrue only matters if the value is not
+  // condition-dependent.
+  bool CondIsTrue = !E->isConditionDependent() && E->isConditionTrue();
+
+  return new (Importer.getToContext())
+      ChooseExpr(ToBuiltinLoc, ToCond, ToLHS, ToRHS, ToType, VK, OK,
+                 ToRParenLoc, CondIsTrue, TypeDependent, ValueDependent);
+}
 
 ExpectedStmt ASTNodeImporter::VisitGNUNullExpr(GNUNullExpr *E) {
   ExpectedType TypeOrErr = import(E->getType());

clang/lib/ASTMatchers/ASTMatchersInternal.cpp

@@ -727,6 +727,7 @@ const internal::VariadicDynCastAllOfMatcher<Stmt, CompoundLiteralExpr>
     compoundLiteralExpr;
 const internal::VariadicDynCastAllOfMatcher<Stmt, CXXNullPtrLiteralExpr>
     cxxNullPtrLiteralExpr;
+const internal::VariadicDynCastAllOfMatcher<Stmt, ChooseExpr> chooseExpr;
 const internal::VariadicDynCastAllOfMatcher<Stmt, GNUNullExpr> gnuNullExpr;
 const internal::VariadicDynCastAllOfMatcher<Stmt, AtomicExpr> atomicExpr;
 const internal::VariadicDynCastAllOfMatcher<Stmt, StmtExpr> stmtExpr;

clang/lib/ASTMatchers/Dynamic/Registry.cpp

@@ -147,6 +147,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(caseStmt);
   REGISTER_MATCHER(castExpr);
   REGISTER_MATCHER(characterLiteral);
+  REGISTER_MATCHER(chooseExpr);
   REGISTER_MATCHER(classTemplateDecl);
   REGISTER_MATCHER(classTemplateSpecializationDecl);
   REGISTER_MATCHER(complexType);

clang/test/ASTMerge/choose-expr/Inputs/choose.c

@@ -0,0 +1,2 @@
+_Static_assert(__builtin_choose_expr(1, 1, 0), "Incorrect semantics of __builtin_choose_expr");
+_Static_assert(__builtin_choose_expr(0, 0, 1), "Incorrect semantics of __builtin_choose_expr");

clang/test/ASTMerge/choose-expr/test.c

@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -std=c11 -emit-pch -o %t.ast %S/Inputs/choose.c
+// RUN: %clang_cc1 -std=c11 -ast-merge %t.ast -fsyntax-only -verify %s
+// expected-no-diagnostics
+

clang/unittests/AST/ASTImporterTest.cpp

@@ -563,6 +563,34 @@ TEST_P(ImportExpr, ImportStringLiteral) {
           stringLiteral(hasType(asString("const char [7]"))))));
 }
 
+TEST_P(ImportExpr, ImportChooseExpr) {
+  MatchVerifier<Decl> Verifier;
+
+  // This case tests C code that is not condition-dependent and has a true
+  // condition.
+  testImport(
+    "void declToImport() { (void)__builtin_choose_expr(1, 2, 3); }",
+    Lang_C, "", Lang_C, Verifier,
+    functionDecl(hasDescendant(chooseExpr())));
+
+  ArgVector Args = getExtraArgs();
+  BindableMatcher<Decl> Matcher =
+      functionTemplateDecl(hasDescendant(chooseExpr()));
+
+  // Don't try to match the template contents if template parsing is delayed.
+  if (llvm::find(Args, "-fdelayed-template-parsing") != Args.end()) {
+    Matcher = functionTemplateDecl();
+  }
+
+  // Make sure that uses of (void)__builtin_choose_expr with dependent types in
+  // the condition are handled properly. This test triggers an assertion if the
+  // ASTImporter incorrectly tries to access isConditionTrue() when
+  // isConditionDependent() is true.
+  testImport("template<int N> void declToImport() { "
+             "(void)__builtin_choose_expr(N, 1, 0); }",
+             Lang_CXX, "", Lang_CXX, Verifier, Matcher);
+}
+
 TEST_P(ImportExpr, ImportGNUNullExpr) {
   MatchVerifier<Decl> Verifier;
   testImport(
@@ -1312,6 +1340,27 @@ TEST_P(ASTImporterOptionSpecificTestBase, ImportCorrectTemplatedDecl) {
   ASSERT_EQ(ToTemplated1, ToTemplated);
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase, ImportChooseExpr) {
+  // This tests the import of isConditionTrue directly to make sure the importer
+  // gets it right.
+  Decl *From, *To;
+  std::tie(From, To) = getImportedDecl(
+    "void declToImport() { (void)__builtin_choose_expr(1, 0, 1); }",
+    Lang_C, "", Lang_C);
+
+  auto ToResults = match(chooseExpr().bind("choose"), To->getASTContext());
+  auto FromResults = match(chooseExpr().bind("choose"), From->getASTContext());
+
+  const ChooseExpr *FromChooseExpr =
+      selectFirst<ChooseExpr>("choose", FromResults);
+  ASSERT_TRUE(FromChooseExpr);
+
+  const ChooseExpr *ToChooseExpr = selectFirst<ChooseExpr>("choose", ToResults);
+  ASSERT_TRUE(ToChooseExpr);
+
+  EXPECT_EQ(FromChooseExpr->isConditionTrue(), ToChooseExpr->isConditionTrue());
+}
+
 TEST_P(ASTImporterOptionSpecificTestBase,
        ImportFunctionWithBackReferringParameter) {
   Decl *From, *To;

clang/unittests/ASTMatchers/ASTMatchersNodeTest.cpp

@@ -754,6 +754,11 @@ TEST(Matcher, NullPtrLiteral) {
   EXPECT_TRUE(matches("int* i = nullptr;", cxxNullPtrLiteralExpr()));
 }
 
+TEST(Matcher, ChooseExpr) {
+  EXPECT_TRUE(matchesC("void f() { (void)__builtin_choose_expr(1, 2, 3); }",
+                       chooseExpr()));
+}
+
 TEST(Matcher, GNUNullExpr) {
   EXPECT_TRUE(matches("int* i = __null;", gnuNullExpr()));
 }