Make return statements single steppable

runtime/vm/intermediate_language_arm.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_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 81 matching lines @@
     ASSERT(fp_sp_dist <= 0);
     __ sub(R2, SP, ShifterOperand(FP));
     __ CompareImmediate(R2, fp_sp_dist);
     __ b(&stack_ok, EQ);
     __ bkpt(0);
     __ Bind(&stack_ok);
   }
 #endif
   __ LeaveDartFrame();
   __ Ret();
-
-  // No need to generate NOP instructions so that the debugger can patch the
-  // return pattern (3 instructions) with a call to the debug stub (also 3
-  // instructions).
-  compiler->AddCurrentDescriptor(PcDescriptors::kReturn,
-                                 Isolate::kNoDeoptId,
-                                 token_pos());
 }
 
 
 static Condition NegateCondition(Condition condition) {
   switch (condition) {
     case EQ: return NE;
     case NE: return EQ;
     case LT: return GE;
     case LE: return GT;
     case GT: return LE;
@@ skipping 609 matching lines @@
 
 LocationSummary* StringFromCharCodeInstr::MakeLocationSummary(bool opt) const {
   const intptr_t kNumInputs = 1;
   // TODO(fschneider): Allow immediate operands for the char code.
   return LocationSummary::Make(kNumInputs,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
 
+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;
+  }
+}
+
+
 void StringFromCharCodeInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register char_code = locs()->in(0).reg();
   Register result = locs()->out().reg();
   __ LoadImmediate(result,
                    reinterpret_cast<uword>(Symbols::PredefinedAddress()));
   __ AddImmediate(result, Symbols::kNullCharCodeSymbolOffset * kWordSize);
   __ ldr(result, Address(result, char_code, LSL, 1));  // Char code is a smi.
 }
 
 
@@ skipping 4098 matching lines @@
   compiler->GenerateCall(token_pos(),
                          &label,
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM