Reorder full code for while loops to better reflect statement positions.

R=jkummerow@chromium.org
BUG=v8:2047
LOG=N

Review URL: https://codereview.chromium.org/353823002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22013 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/full-codegen.cc

@@ -854,11 +854,6 @@ void FullCodeGenerator::SetExpressionPosition(Expression* expr) {
 }
 
 
-void FullCodeGenerator::SetStatementPosition(int pos) {
-  CodeGenerator::RecordPositions(masm_, pos);
-}
-
-
 void FullCodeGenerator::SetSourcePosition(int pos) {
   if (pos != RelocInfo::kNoPosition) {
     masm_->positions_recorder()->RecordPosition(pos);
@@ -1283,31 +1278,28 @@ void FullCodeGenerator::VisitDoWhileStatement(DoWhileStatement* stmt) {
 
 void FullCodeGenerator::VisitWhileStatement(WhileStatement* stmt) {
   Comment cmnt(masm_, "[ WhileStatement");
-  Label test, body;
+  Label loop, body;
 
   Iteration loop_statement(this, stmt);
   increment_loop_depth();
 
-  // Emit the test at the bottom of the loop.
-  __ jmp(&test);
+  __ bind(&loop);
+
+  SetExpressionPosition(stmt->cond());
+  VisitForControl(stmt->cond(),
+                  &body,
+                  loop_statement.break_label(),
+                  &body);
 
   PrepareForBailoutForId(stmt->BodyId(), NO_REGISTERS);
   __ bind(&body);
   Visit(stmt->body());
 
-  // Emit the statement position here as this is where the while
-  // statement code starts.
   __ bind(loop_statement.continue_label());
-  SetStatementPosition(stmt);
 
   // Check stack before looping.
-  EmitBackEdgeBookkeeping(stmt, &body);
-
-  __ bind(&test);
-  VisitForControl(stmt->cond(),
-                  &body,
-                  loop_statement.break_label(),
-                  loop_statement.break_label());
+  EmitBackEdgeBookkeeping(stmt, &loop);
+  __ jmp(&loop);
 
   PrepareForBailoutForId(stmt->ExitId(), NO_REGISTERS);
   __ bind(loop_statement.break_label());

src/full-codegen.h

@@ -562,7 +562,6 @@ class FullCodeGenerator: public AstVisitor {
   void SetReturnPosition(FunctionLiteral* fun);
   void SetStatementPosition(Statement* stmt);
   void SetExpressionPosition(Expression* expr);
-  void SetStatementPosition(int pos);
   void SetSourcePosition(int pos);
 
   // Non-local control flow support.

test/cctest/test-debug.cc

@@ -3193,19 +3193,26 @@ TEST(DebugStepWhile) {
   v8::Local<v8::Function> foo = CompileFunction(&env, src, "foo");
   SetBreakPoint(foo, 8);  // "var a = 0;"
 
+  // Looping 0 times.  We still should break at the while-condition once.
+  step_action = StepIn;
+  break_point_hit_count = 0;
+  v8::Handle<v8::Value> argv_0[argc] = { v8::Number::New(isolate, 0) };
+  foo->Call(env->Global(), argc, argv_0);
+  CHECK_EQ(3, break_point_hit_count);
+
   // Looping 10 times.
   step_action = StepIn;
   break_point_hit_count = 0;
   v8::Handle<v8::Value> argv_10[argc] = { v8::Number::New(isolate, 10) };
   foo->Call(env->Global(), argc, argv_10);
-  CHECK_EQ(22, break_point_hit_count);
+  CHECK_EQ(23, break_point_hit_count);
 
   // Looping 100 times.
   step_action = StepIn;
   break_point_hit_count = 0;
   v8::Handle<v8::Value> argv_100[argc] = { v8::Number::New(isolate, 100) };
   foo->Call(env->Global(), argc, argv_100);
-  CHECK_EQ(202, break_point_hit_count);
+  CHECK_EQ(203, break_point_hit_count);
 
   // Get rid of the debug event listener.
   v8::Debug::SetDebugEventListener(NULL);
@@ -5123,10 +5130,7 @@ static void ThreadedMessageHandler(const v8::Debug::Message& message) {
   if (IsBreakEventMessage(print_buffer)) {
     // Check that we are inside the while loop.
     int source_line = GetSourceLineFromBreakEventMessage(print_buffer);
-    // TODO(2047): This should really be 8 <= source_line <= 13; but we
-    // currently have an off-by-one error when calculating the source
-    // position corresponding to the program counter at the debug break.
-    CHECK(7 <= source_line && source_line <= 13);
+    CHECK(8 <= source_line && source_line <= 13);
     threaded_debugging_barriers.barrier_2.Wait();
   }
 }