Pattern match on generated code to find edge counters.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index 4d2ee9df452a91f832710091b1e2a7f2bae89ad2..4b5562b189f512cbef6133981228a2642667dc98 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -4499,21 +4499,13 @@ void GraphEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 void TargetEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ Bind(compiler->GetJumpLabel(this));
   if (!compiler->is_optimizing()) {
+    compiler->EmitEdgeCounter();
+    // The deoptimization descriptor points after the edge counter code for
+    // uniformity with ARM and MIPS, where we can reuse pattern matching
+    // code that matches backwards from the end of the pattern.
     compiler->AddCurrentDescriptor(PcDescriptors::kDeopt,
                                    deopt_id_,
                                    Scanner::kDummyTokenIndex);
-    // Add an edge counter.
-    const Array& counter = Array::ZoneHandle(Array::New(1, Heap::kOld));
-    counter.SetAt(0, Smi::Handle(Smi::New(0)));
-    Label done;
-    __ Comment("Edge counter");
-    __ LoadObject(RAX, counter, PP);
-    __ AddImmediate(FieldAddress(RAX, Array::element_offset(0)),
-                    Immediate(Smi::RawValue(1)), PP);
-    __ j(NO_OVERFLOW, &done);
-    __ LoadImmediate(FieldAddress(RAX, Array::element_offset(0)),
-                     Immediate(Smi::RawValue(Smi::kMaxValue)), PP);
-    __ Bind(&done);
   }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
@@ -4528,23 +4520,15 @@ LocationSummary* GotoInstr::MakeLocationSummary() const {
 
 void GotoInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   if (!compiler->is_optimizing()) {
-    // Add deoptimization descriptor for deoptimizing instructions that may
-    // be inserted before this instruction.
+    compiler->EmitEdgeCounter();
+    // Add a deoptimization descriptor for deoptimizing instructions that
+    // may be inserted before this instruction.  This descriptor points
+    // after the edge counter for uniformity with ARM and MIPS, where we can
+    // reuse pattern matching that matches backwards from the end of the
+    // pattern.
     compiler->AddCurrentDescriptor(PcDescriptors::kDeopt,
                                    GetDeoptId(),
-                                   0);  // No token position.
-    // Add an edge counter.
-    const Array& counter = Array::ZoneHandle(Array::New(1, Heap::kOld));
-    counter.SetAt(0, Smi::Handle(Smi::New(0)));
-    Label done;
-    __ Comment("Edge counter");
-    __ LoadObject(RAX, counter, PP);
-    __ AddImmediate(FieldAddress(RAX, Array::element_offset(0)),
-                    Immediate(Smi::RawValue(1)), PP);
-    __ j(NO_OVERFLOW, &done);
-    __ LoadImmediate(FieldAddress(RAX, Array::element_offset(0)),
-                     Immediate(Smi::RawValue(Smi::kMaxValue)), PP);
-    __ Bind(&done);
+                                   Scanner::kDummyTokenIndex);
   }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());