[clang-tools-extra] r289912 - [clang-tidy] Do not move parameter if only DeclRefExpr occurs inside of a loop

[Felix Berger via cfe-commits]

Author: flx
Date: Thu Dec 15 20:47:56 2016
New Revision: 289912

URL: http://llvm.org/viewvc/llvm-project?rev=289912&view=rev
Log:
[clang-tidy] Do not move parameter if only DeclRefExpr occurs inside of a loop

Summary: This fixes a bug where the performance-unnecessary-value-param check suggests a fix to move the parameter inside of a loop which could be invoked multiple times.

Reviewers: sbenza, aaron.ballman, alexfh

Subscribers: JDevlieghere, cfe-commits

Differential Revision: https://reviews.llvm.org/D27187

Modified:
    clang-tools-extra/trunk/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
    clang-tools-extra/trunk/test/clang-tidy/performance-unnecessary-value-param.cpp

Modified: clang-tools-extra/trunk/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clang-tidy/performance/UnnecessaryValueParamCheck.cpp?rev=289912&r1=289911&r2=289912&view=diff
==============================================================================
--- clang-tools-extra/trunk/clang-tidy/performance/UnnecessaryValueParamCheck.cpp (original)
+++ clang-tools-extra/trunk/clang-tidy/performance/UnnecessaryValueParamCheck.cpp Thu Dec 15 20:47:56 2016
@@ -47,6 +47,17 @@ bool isReferencedOutsideOfCallExpr(const
   return !Matches.empty();
 }
 
+bool hasLoopStmtAncestor(const DeclRefExpr &DeclRef, const Stmt &Stmt,
+                         ASTContext &Context) {
+  auto Matches =
+      match(findAll(declRefExpr(
+                equalsNode(&DeclRef),
+                unless(hasAncestor(stmt(anyOf(forStmt(), cxxForRangeStmt(),
+                                              whileStmt(), doStmt())))))),
+            Stmt, Context);
+  return Matches.empty();
+}
+
 } // namespace
 
 UnnecessaryValueParamCheck::UnnecessaryValueParamCheck(
@@ -105,6 +116,8 @@ void UnnecessaryValueParamCheck::check(c
   if (!IsConstQualified) {
     auto CanonicalType = Param->getType().getCanonicalType();
     if (AllDeclRefExprs.size() == 1 &&
+        !hasLoopStmtAncestor(**AllDeclRefExprs.begin(), *Function->getBody(),
+                             *Result.Context) &&
         ((utils::type_traits::hasNonTrivialMoveConstructor(CanonicalType) &&
           utils::decl_ref_expr::isCopyConstructorArgument(
               **AllDeclRefExprs.begin(), *Function->getBody(),

Modified: clang-tools-extra/trunk/test/clang-tidy/performance-unnecessary-value-param.cpp
URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/test/clang-tidy/performance-unnecessary-value-param.cpp?rev=289912&r1=289911&r2=289912&view=diff
==============================================================================
--- clang-tools-extra/trunk/test/clang-tidy/performance-unnecessary-value-param.cpp (original)
+++ clang-tools-extra/trunk/test/clang-tidy/performance-unnecessary-value-param.cpp Thu Dec 15 20:47:56 2016
@@ -225,6 +225,15 @@ void PositiveMoveOnCopyAssignment(Expens
   // CHECK-FIXES: F = std::move(E);
 }
 
+// The argument could be moved but is not since copy statement is inside a loop.
+void PositiveNoMoveInsideLoop(ExpensiveMovableType E) {
+  // CHECK-MESSAGES: [[@LINE-1]]:52: warning: the parameter 'E' is copied
+  // CHECK-FIXES: void PositiveNoMoveInsideLoop(const ExpensiveMovableType& E) {
+  for (;;) {
+    auto F = E;
+  }
+}
+
 void PositiveConstRefNotMoveConstructible(ExpensiveToCopyType T) {
   // CHECK-MESSAGES: [[@LINE-1]]:63: warning: the parameter 'T' is copied
   // CHECK-FIXES: void PositiveConstRefNotMoveConstructible(const ExpensiveToCopyType& T) {