Pattern match on generated code to find edge counters.

runtime/vm/intermediate_language_arm.cc

Index: runtime/vm/intermediate_language_arm.cc
diff --git a/runtime/vm/intermediate_language_arm.cc b/runtime/vm/intermediate_language_arm.cc
index 00df26bf9fafd3e72a4b6daabbfb796444a8335f..a7e75b810704132e2ba4e1866dafef3e26c58100 100644
--- a/runtime/vm/intermediate_language_arm.cc
+++ b/runtime/vm/intermediate_language_arm.cc
@@ -4444,9 +4444,6 @@ void GraphEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 void TargetEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ Bind(compiler->GetJumpLabel(this));
   if (!compiler->is_optimizing()) {
-    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)));
@@ -4456,6 +4453,12 @@ void TargetEntryInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     __ adds(IP, IP, ShifterOperand(Smi::RawValue(1)));
     __ LoadImmediate(IP, Smi::RawValue(Smi::kMaxValue), VS);  // If overflow.
     __ str(IP, FieldAddress(R0, Array::element_offset(0)));
+    // On ARM the deoptimization descriptor points after the edge counter
+    // code so that we can reuse the same pattern matching code as at call
+    // sites, which matches backwards from the end of the pattern.
+    compiler->AddCurrentDescriptor(PcDescriptors::kDeopt,
+                                   deopt_id_,
+                                   Scanner::kDummyTokenIndex);
   }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
@@ -4469,6 +4472,25 @@ LocationSummary* GotoInstr::MakeLocationSummary() const {
 
 
 void GotoInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  if (!compiler->is_optimizing()) {
+    // Add an edge counter.
+    const Array& counter = Array::ZoneHandle(Array::New(1, Heap::kOld));
+    counter.SetAt(0, Smi::Handle(Smi::New(0)));
+    __ Comment("Edge counter");
+    __ LoadObject(R0, counter);
+    __ ldr(IP, FieldAddress(R0, Array::element_offset(0)));
+    __ adds(IP, IP, ShifterOperand(Smi::RawValue(1)));
+    __ LoadImmediate(IP, Smi::RawValue(Smi::kMaxValue), VS);  // If overflow.
+    __ str(IP, FieldAddress(R0, Array::element_offset(0)));
+    // Add a deoptimization descriptor for deoptimizing instructions that
+    // may be inserted before this instruction.  On ARM this descriptor
+    // points after the edge counter code so that we can reuse the same
+    // pattern matching code as at call sites, which matches backwards from
+    // the end of the pattern.
+    compiler->AddCurrentDescriptor(PcDescriptors::kDeopt,
+                                   GetDeoptId(),
+                                   0);  // No token position.
+  }
   if (HasParallelMove()) {
     compiler->parallel_move_resolver()->EmitNativeCode(parallel_move());
   }