Implement ReflectionContext::addImage with section finder

Implement a version of addImage that takes in a closure responsible
for finding the sections of interest. This allows for the registration
of metadata even in situations where the object file is not complete
(for example, when generated by the JIT).

Author: augusto2112

include/swift/ABI/ObjectFile.h

@@ -31,7 +31,7 @@ class SwiftObjectFileFormat {
 };
 
 /// Responsible for providing the Mach-O reflection section identifiers.
-class SwiftObjectFileFormatMachO : SwiftObjectFileFormat {
+class SwiftObjectFileFormatMachO : public SwiftObjectFileFormat {
 public:
   llvm::StringRef getSectionName(ReflectionSectionKind section) override {
     switch (section) {
@@ -53,7 +53,7 @@ class SwiftObjectFileFormatMachO : SwiftObjectFileFormat {
 };
 
 /// Responsible for providing the ELF reflection section identifiers.
-class SwiftObjectFileFormatELF : SwiftObjectFileFormat {
+class SwiftObjectFileFormatELF : public SwiftObjectFileFormat {
 public:
   llvm::StringRef getSectionName(ReflectionSectionKind section) override {
     switch (section) {
@@ -75,7 +75,7 @@ class SwiftObjectFileFormatELF : SwiftObjectFileFormat {
 };
 
 /// Responsible for providing the COFF reflection section identifiers
-class SwiftObjectFileFormatCOFF : SwiftObjectFileFormat {
+class SwiftObjectFileFormatCOFF : public SwiftObjectFileFormat {
 public:
   llvm::StringRef getSectionName(ReflectionSectionKind section) override {
     switch (section) {

include/swift/Reflection/ReflectionContext.h

@@ -23,6 +23,7 @@
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/Memory.h"
+#include "llvm/ADT/STLExtras.h"
 
 #include "swift/ABI/Enum.h"
 #include "swift/ABI/ObjectFile.h"
@@ -644,6 +645,47 @@ class ReflectionContext
     return false;
   }
 
+  /// Adds an image using the FindSection closure to find the swift metadata
+  /// sections. \param FindSection
+  ///     Closure that finds sections by name. ReflectionContext is in charge
+  ///     of freeing the memory buffer in the RemoteRef return value.
+  ///     process.
+  /// \return
+  ///     \b True if any of the reflection sections were registered,
+  ///     \b false otherwise.
+  bool addImage(llvm::function_ref<
+                std::pair<RemoteRef<void>, uint64_t>(ReflectionSectionKind)>
+                    FindSection) {
+    auto Sections = {
+        ReflectionSectionKind::fieldmd, ReflectionSectionKind::assocty,
+        ReflectionSectionKind::builtin, ReflectionSectionKind::capture,
+        ReflectionSectionKind::typeref, ReflectionSectionKind::reflstr};
+
+    llvm::SmallVector<std::pair<RemoteRef<void>, uint64_t>, 6> Pairs;
+    for (auto Section : Sections) {
+      Pairs.push_back(FindSection(Section));
+      auto LatestRemoteRef = std::get<RemoteRef<void>>(Pairs.back());
+      if (LatestRemoteRef) {
+        MemoryReader::ReadBytesResult Buffer(
+            LatestRemoteRef.getLocalBuffer(),
+            [](const void *Ptr) { free(const_cast<void *>(Ptr)); });
+
+        savedBuffers.push_back(std::move(Buffer));
+      }
+    }
+
+    // If we didn't find any sections, return.
+    if (llvm::all_of(Pairs, [](const auto &Pair) { return !Pair.first; }))
+      return false;
+
+    ReflectionInfo Info = {
+        {Pairs[0].first, Pairs[0].second}, {Pairs[1].first, Pairs[1].second},
+        {Pairs[2].first, Pairs[2].second}, {Pairs[3].first, Pairs[3].second},
+        {Pairs[4].first, Pairs[4].second}, {Pairs[5].first, Pairs[5].second}};
+    this->addReflectionInfo(Info);
+    return true;
+  }
+
   void addReflectionInfo(ReflectionInfo I) {
     getBuilder().addReflectionInfo(I);
   }