Debugger: use debug break slots to break at function exit.

src/arm/debug-arm.cc

Index: src/arm/debug-arm.cc
diff --git a/src/arm/debug-arm.cc b/src/arm/debug-arm.cc
index c09e17e85901aa4c3e78c697c8528c65733fcc74..05b22e74aa3fea004be7b81c4204be713aac3aeb 100644
--- a/src/arm/debug-arm.cc
+++ b/src/arm/debug-arm.cc
@@ -12,49 +12,62 @@
 namespace v8 {
 namespace internal {
 
-void BreakLocation::SetDebugBreakAtReturn() {
-  // Patch the code changing the return from JS function sequence from
-  //   mov sp, fp
-  //   ldmia sp!, {fp, lr}
-  //   add sp, sp, #4
-  //   bx lr
-  // to a call to the debug break return code.
-  //   ldr ip, [pc, #0]
-  //   blx ip
-  //   <debug break return code entry point address>
-  //   bkpt 0
-  CodePatcher patcher(pc(), Assembler::kJSReturnSequenceInstructions);
-  patcher.masm()->ldr(v8::internal::ip, MemOperand(v8::internal::pc, 0));
-  patcher.masm()->blx(v8::internal::ip);
-  patcher.Emit(
-      debug_info_->GetIsolate()->builtins()->Return_DebugBreak()->entry());
-  patcher.masm()->bkpt(0);
+#define __ ACCESS_MASM(masm)
+
+
+void EmitDebugBreakSlot(MacroAssembler* masm) {
+  Label check_size;
+  __ bind(&check_size);
+  for (int i = 0; i < Assembler::kDebugBreakSlotInstructions; i++) {
+    __ nop(MacroAssembler::DEBUG_BREAK_NOP);
+  }
+  DCHECK_EQ(Assembler::kDebugBreakSlotInstructions,
+            masm->InstructionsGeneratedSince(&check_size));
 }
 
 
-void BreakLocation::SetDebugBreakAtSlot() {
-  DCHECK(IsDebugBreakSlot());
+void DebugCodegen::GenerateSlot(MacroAssembler* masm, RelocInfo::Mode mode,
+                                int call_argc) {
+  // Generate enough nop's to make space for a call instruction. Avoid emitting
+  // the constant pool in the debug break slot code.
+  Assembler::BlockConstPoolScope block_const_pool(masm);
+  masm->RecordDebugBreakSlot(mode, call_argc);
+  EmitDebugBreakSlot(masm);
+}
+
+
+void DebugCodegen::ClearDebugBreakSlot(Address pc) {
+  CodePatcher patcher(pc, Assembler::kDebugBreakSlotInstructions);
+  EmitDebugBreakSlot(patcher.masm());
+}
+
+
+void DebugCodegen::PatchDebugBreakSlot(Address pc, Handle<Code> code) {
+  DCHECK_EQ(Code::BUILTIN, code->kind());
+  CodePatcher patcher(pc, Assembler::kDebugBreakSlotInstructions);
   // Patch the code changing the debug break slot code from
   //   mov r2, r2
   //   mov r2, r2
   //   mov r2, r2
+  //   mov r2, r2
   // to a call to the debug break slot code.
   //   ldr ip, [pc, #0]
-  //   blx ip
+  //   b skip
   //   <debug break slot code entry point address>
-  CodePatcher patcher(pc(), Assembler::kDebugBreakSlotInstructions);
-  patcher.masm()->ldr(v8::internal::ip, MemOperand(v8::internal::pc, 0));
-  patcher.masm()->blx(v8::internal::ip);
-  patcher.Emit(
-      debug_info_->GetIsolate()->builtins()->Slot_DebugBreak()->entry());
+  //   skip:
+  //   blx ip
+  Label skip_constant;
+  patcher.masm()->ldr(ip, MemOperand(v8::internal::pc, 0));
+  patcher.masm()->b(&skip_constant);
+  patcher.Emit(code->entry());
+  patcher.masm()->bind(&skip_constant);
+  patcher.masm()->blx(ip);
 }
 
 
-#define __ ACCESS_MASM(masm)
-
-
-static void Generate_DebugBreakCallHelper(MacroAssembler* masm,
-                                          RegList object_regs) {
+void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
+                                          DebugBreakCallHelperMode mode) {
+  __ RecordComment("Debug break");
   {
     FrameAndConstantPoolScope scope(masm, StackFrame::INTERNAL);
 
@@ -66,36 +79,23 @@ static void Generate_DebugBreakCallHelper(MacroAssembler* masm,
     __ mov(ip, Operand(Smi::FromInt(LiveEdit::kFramePaddingInitialSize)));
     __ push(ip);
 
-    // Store the registers containing live values on the expression stack to
-    // make sure that these are correctly updated during GC. Non object values
-    // are stored as a smi causing it to be untouched by GC.
-    DCHECK((object_regs & ~kJSCallerSaved) == 0);
-    if (object_regs != 0) {
-      __ stm(db_w, sp, object_regs);
-    }
+    if (mode == SAVE_RESULT_REGISTER) __ push(r0);
 
-#ifdef DEBUG
-    __ RecordComment("// Calling from debug break to runtime - come in - over");
-#endif
     __ mov(r0, Operand::Zero());  // no arguments
     __ mov(r1, Operand(ExternalReference::debug_break(masm->isolate())));
 
     CEntryStub ceb(masm->isolate(), 1);
     __ CallStub(&ceb);
 
-    // Restore the register values from the expression stack.
-    if (object_regs != 0) {
-      __ ldm(ia_w, sp, object_regs);
-    }
-
-    for (int i = 0; i < kNumJSCallerSaved; i++) {
-      int r = JSCallerSavedCode(i);
-      Register reg = {r};
-      if (FLAG_debug_code && ((object_regs & (1 << r)) == 0)) {
+    if (FLAG_debug_code) {
+      for (int i = 0; i < kNumJSCallerSaved; i++) {
+        Register reg = {JSCallerSavedCode(i)};
         __ mov(reg, Operand(kDebugZapValue));
       }
     }
 
+    if (mode == SAVE_RESULT_REGISTER) __ pop(r0);
+
     // Don't bother removing padding bytes pushed on the stack
     // as the frame is going to be restored right away.
 
@@ -113,38 +113,6 @@ static void Generate_DebugBreakCallHelper(MacroAssembler* masm,
 }
 
 
-void DebugCodegen::GenerateReturnDebugBreak(MacroAssembler* masm) {
-  // In places other than IC call sites it is expected that r0 is TOS which
-  // is an object - this is not generally the case so this should be used with
-  // care.
-  Generate_DebugBreakCallHelper(masm, r0.bit());
-}
-
-
-void DebugCodegen::GenerateSlot(MacroAssembler* masm,
-                                DebugCodegen::SlotLocation location,
-                                int call_argc) {
-  // Generate enough nop's to make space for a call instruction. Avoid emitting
-  // the constant pool in the debug break slot code.
-  Assembler::BlockConstPoolScope block_const_pool(masm);
-  Label check_codesize;
-  __ bind(&check_codesize);
-  RecordRelocInfo(masm, location, call_argc);
-  for (int i = 0; i < Assembler::kDebugBreakSlotInstructions; i++) {
-    __ nop(MacroAssembler::DEBUG_BREAK_NOP);
-  }
-  DCHECK_EQ(Assembler::kDebugBreakSlotInstructions,
-            masm->InstructionsGeneratedSince(&check_codesize));
-}
-
-
-void DebugCodegen::GenerateSlotDebugBreak(MacroAssembler* masm) {
-  // In the places where a debug break slot is inserted no registers can contain
-  // object pointers.
-  Generate_DebugBreakCallHelper(masm, 0);
-}
-
-
 void DebugCodegen::GeneratePlainReturnLiveEdit(MacroAssembler* masm) {
   __ Ret();
 }