Make return statements single steppable

runtime/vm/intermediate_language_ia32.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 80 matching lines @@
     __ movl(EDI, ESP);
     __ subl(EDI, EBP);
     __ cmpl(EDI, Immediate(fp_sp_dist));
     __ j(EQUAL, &done, Assembler::kNearJump);
     __ int3();
     __ Bind(&done);
   }
 #endif
   __ LeaveFrame();
   __ ret();
-
-  // Generate 1 byte NOP so that the debugger can patch the
-  // return pattern with a call to the debug stub.
-  __ nop(1);
-  compiler->AddCurrentDescriptor(PcDescriptors::kReturn,
-                                 Isolate::kNoDeoptId,
-                                 token_pos());
 }
 
 
 LocationSummary* LoadLocalInstr::MakeLocationSummary(bool opt) const {
   const intptr_t kNumInputs = 0;
   return LocationSummary::Make(kNumInputs,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
@@ skipping 583 matching lines @@
       (is_bootstrap_native()) ? &StubCode::CallBootstrapCFunctionLabel() :
                                 &StubCode::CallNativeCFunctionLabel();
   compiler->GenerateCall(token_pos(),
                          stub_entry,
                          PcDescriptors::kOther,
                          locs());
   __ popl(result);
 }
 
 
+LocationSummary* DebugStepCheckInstr::MakeLocationSummary(bool opt) const {
+  const intptr_t kNumInputs = 0;
+  const intptr_t kNumTemps = 0;
+  LocationSummary* locs =
+      new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kCall);
+  return locs;
+}
+
+
+void DebugStepCheckInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  if (!compiler->is_optimizing()) {
+    const ExternalLabel label("debug_step_check",
+                              StubCode::DebugStepCheckEntryPoint());
+    compiler->GenerateCall(token_pos(),
+                           &label,
+                           PcDescriptors::kReturn,
+                           locs());
+  }
+}
+
+
+Instruction* DebugStepCheckInstr::Canonicalize(FlowGraph* flow_graph) {
+  if (compiler->is_optimizing()) {
+    return NULL;
+  }
+}
+
+
 static bool CanBeImmediateIndex(Value* value, intptr_t cid) {
   ConstantInstr* constant = value->definition()->AsConstant();
   if ((constant == NULL) || !Assembler::IsSafeSmi(constant->value())) {
     return false;
   }
   const int64_t index = Smi::Cast(constant->value()).AsInt64Value();
   const intptr_t scale = FlowGraphCompiler::ElementSizeFor(cid);
   const intptr_t offset = FlowGraphCompiler::DataOffsetFor(cid);
   const int64_t displacement = index * scale + offset;
   return Utils::IsInt(32, displacement);
@@ skipping 4523 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32