Improve loop convert's variable aliasing

Loop convert's variable name aliasing may cause issues if the variable is
declared as a value (copy). The converted loop will declare the variable as a
reference which may inadvertently cause modifications to the container if it
were used and modified as a temporary copy.

This is fixed by preserving the reference or value qualifiers of the aliased
variable. That is, if the variable was declared as a value the loop variable
will also be declared as a value and similarly for references.

Fixes: PR15600
Author: Jack Yang <jack.yang@intel.com>
llvm-svn: 178485

1 files changed, 37 insertions, 0 deletions

diff --git a/clang-tools-extra/test/cpp11-migrate/LoopConvert/naming-alias.cpp b/clang-tools-extra/test/cpp11-migrate/LoopConvert/naming-alias.cpp
index 89485059f76..0373d2b7473 100644
--- a/clang-tools-extra/test/cpp11-migrate/LoopConvert/naming-alias.cpp
+++ b/clang-tools-extra/test/cpp11-migrate/LoopConvert/naming-alias.cpp
@@ -57,3 +57,40 @@ void aliasing() {
   // CHECK-NEXT: Val &t = func(elem);
   // CHECK-NEXT: int y = t.x;
 }
+
+void refs_and_vals() {
+  // The following tests check that the transform correctly preserves the
+  // reference or value qualifiers of the aliased variable. That is, if the
+  // variable was declared as a value, the loop variable will be declared as a
+  // value and vice versa for references.
+
+  S s;
+  const S s_const = s;
+
+  for (S::const_iterator it = s_const.begin(); it != s_const.end(); ++it) {
+    MutableVal alias = *it; { }
+    alias.x = 0;
+  }
+  // CHECK: for (auto alias : s_const)
+  // CHECK-NOT: MutableVal {{[a-z_]+}} =
+  // CHECK-NEXT: { }
+  // CHECK-NEXT: alias.x = 0;
+
+  for (S::iterator it = s.begin(), e = s.end(); it != e; ++it) {
+    MutableVal alias = *it; { }
+    alias.x = 0;
+  }
+  // CHECK: for (auto alias : s)
+  // CHECK-NOT: MutableVal {{[a-z_]+}} =
+  // CHECK-NEXT: { }
+  // CHECK-NEXT: alias.x = 0;
+
+  for (S::iterator it = s.begin(), e = s.end(); it != e; ++it) {
+    MutableVal &alias = *it; { }
+    alias.x = 0;
+  }
+  // CHECK: for (auto & alias : s)
+  // CHECK-NOT: MutableVal &{{[a-z_]+}} =
+  // CHECK-NEXT: { }
+  // CHECK-NEXT: alias.x = 0;
+}