Deoptimize functions before setting breakpoints

runtime/vm/debugger.cc

Index: runtime/vm/debugger.cc
===================================================================
--- runtime/vm/debugger.cc	(revision 5364)
+++ runtime/vm/debugger.cc	(working copy)
@@ -485,7 +485,24 @@
 }
 
 
-void Debugger::InstrumentForStepping(const Function &target_function) {
+// Deoptimize function if necessary. Does not patch return addresses on the
+// stack. If there are activation frames of this function on the stack,
+// the optimized code will be executed when the callee returns.
+void Debugger::EnsureFunctionIsDeoptimized(const Function& func) {
+  if (func.HasOptimizedCode()) {
+    if (verbose) {
+      printf("Deoptimizing function %s\n",

[srdjan, 2012/03/13 17:11:35]

OS::Print

[hausner, 2012/03/13 20:45:03]

Done.

+          String::Handle(func.name()).ToCString());
+    }
+    func.set_usage_counter(0);
+    func.set_deoptimization_counter(func.deoptimization_counter() + 1);

[srdjan, 2012/03/13 17:11:35]

Don't increase the counter otherwise setting and clearing the breakpoint would
prevent future optimizations. The deopt counter is here to stop endless
deoptimizations of certain bad-behaving methods,

[hausner, 2012/03/13 20:45:03]

Done.

+    Compiler::CompileFunction(func);
+    ASSERT(!func.HasOptimizedCode());
+  }
+}
+
+
+void Debugger::InstrumentForStepping(const Function& target_function) {
   if (!target_function.HasCode()) {
     Compiler::CompileFunction(target_function);
     // If there were any errors, ignore them silently and return without
@@ -493,8 +510,9 @@
     if (!target_function.HasCode()) {
       return;
     }
+  } else {
+    EnsureFunctionIsDeoptimized(target_function);

[srdjan, 2012/03/13 17:11:35]

I rather think positive:

if (target.HasCode()) {
  EnsureFunctionIsDeoptimized(target_function);
} else {
  ...
}

[hausner, 2012/03/13 20:45:03]

The glass is now half full.

On 2012/03/13 17:11:35, srdjan wrote:

   }
-  ASSERT(!target_function.HasOptimizedCode());
   Code& code = Code::Handle(target_function.unoptimized_code());
   ASSERT(!code.IsNull());
   PcDescriptors& desc = PcDescriptors::Handle(code.pc_descriptors());
@@ -563,6 +581,7 @@
     // The given token position is not within the target function.
     return NULL;
   }
+  EnsureFunctionIsDeoptimized(target_function);
   SourceBreakpoint* bpt = GetSourceBreakpoint(target_function, token_index);
   if (bpt != NULL) {
     // A breakpoint for this location already exists, return it.