Added flag --inline_smi_string_hashcode and --inline_smi_string_hashcode_ratio to decide when/if sh…

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index 6632df81ee0d88310c547462cd99173c52346506..4a1f51a7895ce1eaa51d4186d46e603ca75e2cc0 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -32,6 +32,10 @@ namespace dart {
 
 DEFINE_FLAG(bool, enable_simd_inline, true,
     "Enable inlining of SIMD related method calls.");
+DEFINE_FLAG(bool, inline_smi_string_hashcode, true,
+    "Inline hashcode for Smi and one-byte strings in case of megamorphic call");
+DEFINE_FLAG(int, inline_smi_string_hashcode_ratio, 50,
+    "Minimal hotness (0..100) of one-byte-string before inlining its hashcode");
 DEFINE_FLAG(int, min_optimization_counter_threshold, 5000,
     "The minimum invocation count for a function.");
 DEFINE_FLAG(int, optimization_counter_scale, 2000,
@@ -157,6 +161,21 @@ void CompilerDeoptInfo::EmitMaterializations(Environment* env,
 }
 
 
+bool FlowGraphCompiler::ShouldInlineSmiStringHashCode(const ICData& ic_data) {
+  if (!FLAG_inline_smi_string_hashcode) return false;

[zra, 2016/04/27 16:28:17]

Please add curly braces. Maybe also merge with the if below that also returns
false.

[srdjan, 2016/04/27 18:10:22]

Done.

+  if (ic_data.target_name() != Symbols::hashCode().raw()) return false;
+  // Precompiled code has no ICData, optimistically inline it.
+  if (ic_data.IsNull() || (ic_data.NumberOfChecks() == 0)) return true;

[zra, 2016/04/27 16:28:17]

ditto.

[srdjan, 2016/04/27 18:10:22]

Done.

+  // Check if OneByteString is hot enough.

[zra, 2016/04/27 16:28:17]

Sorry if I'm confused. So Smi hashcode will only be inlined if OneByteString is
hot?

[srdjan, 2016/04/27 18:10:22]

Yes, because Smi test must be done anyway.  Added comment TODO.

Also added 'lost' check that the hottest class is OnebyteString,

+  const ICData& ic_data_sorted =
+      ICData::Handle(ic_data.AsUnaryClassChecksSortedByCount());
+  ASSERT(ic_data_sorted.NumberOfChecks() > 0);
+  const intptr_t total_count = ic_data_sorted.AggregateCount();
+  const intptr_t ratio = ic_data_sorted.GetCountAt(0) * 100 / total_count;

[zra, 2016/04/27 16:28:17]

Maybe add parens around the multiply.

[srdjan, 2016/04/27 18:10:22]

Done.

+  return ratio > FLAG_inline_smi_string_hashcode_ratio;
+}
+
+
 FlowGraphCompiler::FlowGraphCompiler(
     Assembler* assembler,
     FlowGraph* flow_graph,