Allow SmallVector to be used as a yaml sequence

[zturner]

Summary

Currently YAML sequences require std::vectors. All of the methods that the YAML parser accesses though are present in SmallVector, so there's no reason we can't support SmallVector inherently. This patch does that.

[majnemer]

include/llvm/Support/YAMLTraits.h

1362–1382

Is this formatted right? it looks funny to me for some reason.

1381

Where is flow used?

1394

Shouldn't this be unsigned to match SmallVector's template?

1412

Ditto.

[zturner]

include/llvm/Support/YAMLTraits.h

1362–1382

It's clang-formatted, so I guess so. Which party looks funny?

1381

It seems to be used to distinguish a flow sequence from a regular sequence. I don't know how it's used, other than to say that it's an optional member that if defined, causes the parser to treat it differently. See line 47 of this file.

That said, FlowSequenceTraitsImpl and SequenceTraitsImpl are identical with the exception of the existence of the flow variable. So I'm going to remove this class and consolidate. New patch incoming shortly.

1394

Yes, good catch.

[majnemer]

LGTM with nits.

include/llvm/Support/YAMLTraits.h

1362

My clang-format would put this on its own line.

[ovyalov]

Looks like this CL broke LLDB cmake buildbot - http://lab.llvm.org:8011/builders/lldb-x86_64-ubuntu-14.04-cmake/builds/17873/steps/ninja%20build%20local/logs/stdio, could you take a look?

include/llvm/Support/YAMLTraits.h

 template <typename T>
 inline
 typename std::enable_if<missingTraits<T>::value, Output &>::type
 operator<<(Output &yout, T &seq) {
   char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
   return yout;
 }
 
+template <typename T> struct SequenceTraitsImpl {
+  typedef typename T::value_type _type;
+  static size_t size(IO &io, T &seq) { return seq.size(); }
+  static _type &element(IO &io, T &seq, size_t index) {
+    if (index >= seq.size())
+      seq.resize(index + 1);
+    return seq[index];
+  }
+};
+
 } // namespace yaml
 } // namespace llvm
 
 /// Utility for declaring that a std::vector of a particular type
 /// should be considered a YAML sequence.
-#define LLVM_YAML_IS_SEQUENCE_VECTOR(_type)                                 \
-  namespace llvm {                                                          \
-  namespace yaml {                                                          \
-    template<>                                                              \
-    struct SequenceTraits< std::vector<_type> > {                           \
-      static size_t size(IO &io, std::vector<_type> &seq) {                 \
-        return seq.size();                                                  \
-      }                                                                     \
-      static _type& element(IO &io, std::vector<_type> &seq, size_t index) {\
-        if ( index >= seq.size() )                                          \
-          seq.resize(index+1);                                              \
-        return seq[index];                                                  \
-      }                                                                     \
-    };                                                                      \
-  }                                                                         \
+#define LLVM_YAML_IS_SEQUENCE_VECTOR(_type)                                    \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <>                                                                  \
+  struct SequenceTraits<std::vector<_type>>                                    \
+      : public SequenceTraitsImpl<std::vector<_type>> {};                      \
+  template <unsigned N>                                                        \
+  struct SequenceTraits<SmallVector<_type, N>>                                 \
+      : public SequenceTraitsImpl<SmallVector<_type, N>> {};                   \
+  }                                                                            \
   }
 
 /// Utility for declaring that a std::vector of a particular type
 /// should be considered a YAML flow sequence.
-#define LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(_type)                            \
-  namespace llvm {                                                          \
-  namespace yaml {                                                          \
-    template<>                                                              \
-    struct SequenceTraits< std::vector<_type> > {                           \
-      static size_t size(IO &io, std::vector<_type> &seq) {                 \
-        return seq.size();                                                  \
-      }                                                                     \
-      static _type& element(IO &io, std::vector<_type> &seq, size_t index) {\
-        (void)flow; /* Remove this workaround after PR17897 is fixed */     \
-        if ( index >= seq.size() )                                          \
-          seq.resize(index+1);                                              \
-        return seq[index];                                                  \
-      }                                                                     \
-      static const bool flow = true;                                        \
-    };                                                                      \
-  }                                                                         \
+#define LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(_type)                               \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <unsigned N>                                                        \
+  struct SequenceTraits<SmallVector<_type, N>>                                 \
+      : public SequenceTraitsImpl<SmallVector<_type, N>> {                     \
+    static const bool flow = true;                                             \
+  };                                                                           \
+  template <>                                                                  \
+  struct SequenceTraits<std::vector<_type>>                                    \
+      : public SequenceTraitsImpl<std::vector<_type>> {                        \
+    static const bool flow = true;                                             \
+  };                                                                           \
+  }                                                                            \
   }
 
 /// Utility for declaring that a std::vector of a particular type
 /// should be considered a YAML document list.
-#define LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(_type)                            \
-  namespace llvm {                                                          \
-  namespace yaml {                                                          \
-    template<>                                                              \
-    struct DocumentListTraits< std::vector<_type> > {                       \
-      static size_t size(IO &io, std::vector<_type> &seq) {                 \
-        return seq.size();                                                  \
-      }                                                                     \
-      static _type& element(IO &io, std::vector<_type> &seq, size_t index) {\
-        if ( index >= seq.size() )                                          \
-          seq.resize(index+1);                                              \
-        return seq[index];                                                  \
-      }                                                                     \
-    };                                                                      \
-  }                                                                         \
+#define LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(_type)                               \
+  namespace llvm {                                                             \
+  namespace yaml {                                                             \
+  template <unsigned N>                                                        \
+  struct DocumentListTraits<SmallVector<_type, N>>                             \
+      : public SequenceTraitsImpl<SmallVector<_type, N>> {};                   \
+  template <>                                                                  \
+  struct DocumentListTraits<std::vector<_type>>                                \
+      : public SequenceTraitsImpl<std::vector<_type>> {};                      \
+  }                                                                            \
   }
 
 #endif // LLVM_SUPPORT_YAMLTRAITS_H