[Courgette] Simplify EncodedProgram Label addition code; removed "1.01 x" memory fix.

This CL simplifies how Labels get flattened to a list of RVAs. In the past
EncodedProgram used DefineAbs32Label() / DefineRel32Label(), which let callers
add one Label at a time. Complexity arose from:
- Function pointer usage to avoid duplicate code for abs32 and rel32.
- Need for EncodedProgram to dynamically adjust size of RVA list. This led to
  inefficient array resizing, which was fixed by the "1.01 x" memory growth.

Change: We now pass the collection of abs32 and rel32 Labels to EncodedProgram.
This simplifies the interface, and allows EncodedProgram to find the max indexes
and preallocated buffers. The trade-off is increased test code complexity, since
we'd need to create Label collection.

Other changes:
- Update namespace{} for EncodedProgram and its tests.
- Add more Label constructors (for testing).
- Add LabelManager::GetIndexBound(), for LabelVector and RVAToLabel.
- Add kUnassignedRVA in image_utils.h, with checks for its absence in images.

Review URL: https://codereview.chromium.org/1571913003

Cr-Commit-Position: refs/heads/master@{#370200}

1 files changed, 22 insertions, 7 deletions

diff --git a/courgette/label_manager.cc b/courgette/label_manager.cc
index 268bda2..bd568b0 100644
--- a/courgette/label_manager.cc
+++ b/courgette/label_manager.cc
@@ -20,21 +20,34 @@ LabelManager::LabelManager() {}
 
 LabelManager::~LabelManager() {}
 
-LabelManagerImpl::RvaVisitor::~RvaVisitor() {}
+// static
+int LabelManager::GetIndexBound(const LabelVector& labels) {
+  int max_index = -1;
+  for (const Label& label : labels) {
+    if (label.index_ != Label::kNoIndex)
+      max_index = std::max(max_index, label.index_);
+  }
+  return max_index + 1;
+}
 
-LabelManagerImpl::SimpleIndexAssigner::SimpleIndexAssigner(LabelVector* labels)
-    : labels_(labels) {
-  // Find the maximum assigned index. Not bounded by |labels_| size.
+// static
+int LabelManager::GetIndexBound(const RVAToLabel& labels_map) {
   int max_index = -1;
-  for (const Label& label : *labels_) {
+  for (const auto& rva_and_label : labels_map) {
+    const Label& label = *rva_and_label.second;
     if (label.index_ != Label::kNoIndex)
       max_index = std::max(max_index, label.index_);
   }
+  return max_index + 1;
+}
+
+LabelManagerImpl::RvaVisitor::~RvaVisitor() {}
 
+LabelManagerImpl::SimpleIndexAssigner::SimpleIndexAssigner(LabelVector* labels)
+    : labels_(labels) {
   // Initialize |num_index_| and |available_|.
-  CHECK_GE(max_index + 1, 0);
   num_index_ = std::max(base::checked_cast<int>(labels_->size()),
-                        max_index + 1);
+                        LabelManager::GetIndexBound(*labels_));
   available_.resize(num_index_, true);
   size_t used = 0;
   for (const Label& label : *labels_) {
@@ -129,6 +142,8 @@ void LabelManagerImpl::Read(RvaVisitor* rva_visitor) {
   // Sort |rvas|, then count the number of distinct values.
   using CRV = ConsecutiveRangeVisitor<std::vector<RVA>::iterator>;
   std::sort(rvas.begin(), rvas.end());
+  DCHECK(rvas.empty() || rvas.back() != kUnassignedRVA);
+
   size_t num_distinct_rva = 0;
   for (CRV it(rvas.begin(), rvas.end()); it.has_more(); it.advance())
     ++num_distinct_rva;