VM(RegExp): Allow OSR optimization of RegExp :matcher functions.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index f5a702a4b622834bf5e2607a3194e15aef3ed489..09f67c56e73ed114b5d3ecfee167a127cb4efaff 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -168,17 +168,20 @@ FlowGraph* IrregexpCompilationPipeline::BuildFlowGraph(
     const ZoneGrowableArray<const ICData*>& ic_data_array,
     intptr_t osr_id) {
   // Compile to the dart IR.
-  RegExpEngine::CompilationResult result = RegExpEngine::CompileIR(
-      parsed_function->regexp_compile_data(), parsed_function, ic_data_array);
+  RegExpEngine::CompilationResult result =
+      RegExpEngine::CompileIR(parsed_function->regexp_compile_data(),
+                              parsed_function, ic_data_array, osr_id);
   backtrack_goto_ = result.backtrack_goto;
 
   // Allocate variables now that we know the number of locals.
   parsed_function->AllocateIrregexpVariables(result.num_stack_locals);
 
-  // Build the flow graph.
-  FlowGraphBuilder builder(*parsed_function, ic_data_array,
-                           /* not building var desc */ NULL,
-                           /* not inlining */ NULL, osr_id);
+  // When compiling for OSR, use a depth first search to prune instructions

[erikcorry, 2017/06/22 13:08:06]

Actually "use a depth first search to find the entry point.  Later, the
instructions not reachable from the entry point will be pruned by
DiscoverBlocks.

Is this the right understanding.  I think this method should be called "Attach
OSR Entry Point" since it doesn't actually prune anything, if I've understood it
right.

[Vyacheslav Egorov (Google), 2017/06/22 14:58:48]

Renamed to RelinkToOsrEntry()

+  // unreachable from the OSR entry. Catch entries are always considered
+  // reachable, even if they become unreachable after OSR.
+  if (osr_id != Compiler::kNoOSRDeoptId) {
+    result.graph_entry->PruneUnreachableForOSR(zone, result.num_blocks);
+  }
 
   return new (zone)
       FlowGraph(*parsed_function, result.graph_entry, result.num_blocks);