Add stream helper to output any iterable collection

{PrintCollection} can print any collection which is iterable via a
standard for-each loop in C++. The output format of {4, 7, 11} is:
[4, 7, 11]

This helper avoids a few repetitions of manually outputting such
collections.

R=titzer@chromium.org

Bug: v8:7754
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Iaa91e5465968a029815b3aa2b35948f711956cdb
Reviewed-on: https://chromium-review.googlesource.com/1112005
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54048}

src/heap/object-stats.cc

@@ -150,12 +150,7 @@ V8_NOINLINE static void PrintJSONArray(size_t* array, const int len) {
 
 V8_NOINLINE static void DumpJSONArray(std::stringstream& stream, size_t* array,
                                       const int len) {
-  stream << "[";
-  for (int i = 0; i < len; i++) {
-    stream << array[i];
-    if (i != (len - 1)) stream << ",";
-  }
-  stream << "]";
+  stream << PrintCollection(Vector<size_t>(array, len));
 }
 
 void ObjectStats::PrintKeyAndId(const char* key, int gc_count) {

src/ostreams.h

@@ -115,6 +115,23 @@ struct AsHexBytes {
   ByteOrder byte_order;
 };
 
+template <typename T>
+struct PrintIteratorRange {
+  T start;
+  T end;
+  PrintIteratorRange(T start, T end) : start(start), end(end) {}
+};
+
+// Print any collection which can be iterated via std::begin and std::end.
+// {Iterator} is the common type of {std::begin} and {std::end} called on a
+// {const T&}. This function is only instantiable if that type exists.
+template <typename T, typename Iterator = typename std::common_type<
+                          decltype(std::begin(std::declval<const T&>())),
+                          decltype(std::end(std::declval<const T&>()))>::type>
+PrintIteratorRange<Iterator> PrintCollection(const T& collection) {
+  return {std::begin(collection), std::end(collection)};
+}
+
 // Writes the given character to the output escaping everything outside of
 // printable/space ASCII range. Additionally escapes '\' making escaping
 // reversible.
@@ -136,6 +153,17 @@ V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& os, const AsHex& v);
 V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& os,
                                            const AsHexBytes& v);
 
+template <typename T>
+std::ostream& operator<<(std::ostream& os, const PrintIteratorRange<T>& range) {
+  const char* comma = "";
+  os << "[";
+  for (T it = range.start; it != range.end; ++it, comma = ", ") {
+    os << comma << *it;
+  }
+  os << "]";
+  return os;
+}
+
 }  // namespace internal
 }  // namespace v8
 

src/wasm/baseline/liftoff-assembler.cc

@@ -614,17 +614,11 @@ bool LiftoffAssembler::ValidateCacheState() const {
   if (valid) return true;
   std::ostringstream os;
   os << "Error in LiftoffAssembler::ValidateCacheState().\n";
-  os << "expected: used_regs " << used_regs << ", counts [";
-  for (int reg = 0; reg < kAfterMaxLiftoffRegCode; ++reg) {
-    os << (reg == 0 ? "" : ", ") << register_use_count[reg];
-  }
-  os << "]\n";
-  os << "found:    used_regs " << cache_state_.used_registers << ", counts [";
-  for (int reg = 0; reg < kAfterMaxLiftoffRegCode; ++reg) {
-    os << (reg == 0 ? "" : ", ") << cache_state_.register_use_count[reg];
-  }
-  os << "]\n";
-  os << "Use --trace-liftoff to debug.\n";
+  os << "expected: used_regs " << used_regs << ", counts "
+     << PrintCollection(register_use_count) << "\n";
+  os << "found:    used_regs " << cache_state_.used_registers << ", counts "
+     << PrintCollection(cache_state_.register_use_count) << "\n";
+  os << "Use --trace-liftoff to debug.";
   FATAL("%s", os.str().c_str());
 }
 

src/wasm/baseline/liftoff-compiler.cc

@@ -1807,11 +1807,7 @@ class LiftoffCompiler {
           control_depth == -1
               ? asm_->cache_state()
               : &decoder->control_at(control_depth)->label_state;
-      bool first = true;
-      for (LiftoffAssembler::VarState& slot : cache_state->stack_state) {
-        os << (first ? "" : "-") << slot;
-        first = false;
-      }
+      os << PrintCollection(cache_state->stack_state);
       if (control_depth != -1) PrintF("; ");
     }
     os << "\n";

test/cctest/test-intl.cc

@@ -18,17 +18,6 @@ namespace internal {
 bool operator==(const NumberFormatSpan& lhs, const NumberFormatSpan& rhs) {
   return memcmp(&lhs, &rhs, sizeof(lhs)) == 0;
 }
-template <typename _CharT, typename _Traits, typename T>
-std::basic_ostream<_CharT, _Traits>& operator<<(
-    std::basic_ostream<_CharT, _Traits>& self, const std::vector<T>& v) {
-  self << "[";
-  for (auto it = v.begin(); it < v.end();) {
-    self << *it;
-    it++;
-    if (it < v.end()) self << ", ";
-  }
-  return self << "]";
-}
 template <typename _CharT, typename _Traits>
 std::basic_ostream<_CharT, _Traits>& operator<<(
     std::basic_ostream<_CharT, _Traits>& self, const NumberFormatSpan& part) {