[sparkplug] Fix GetBytecodeOffsetForBaselinePC() in prologue

When GetBytecodeOffsetForBaselinePC() is called with a PC that is inside
the baseline prologue, correctly return kFunctionEntryOffset now.

Bug: v8:11420
Change-Id: I39cb96a04e7d92d0ba5dfcbcaeebd23144c9df05
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2773050
Auto-Submit: Patrick Thier <pthier@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73601}

src/baseline/bytecode-offset-iterator.cc

@@ -47,8 +47,11 @@ BytecodeOffsetIterator::~BytecodeOffsetIterator() {
 }
 
 void BytecodeOffsetIterator::Initialize() {
-  current_pc_start_offset_ = ReadPosition();
-  current_pc_end_offset_ = current_pc_start_offset_ + ReadPosition();
+  // Initialize values for the prologue.
+  // The first recorded position is at the start of the first bytecode.
+  current_pc_start_offset_ = 0;
+  current_pc_end_offset_ = ReadPosition();
+  current_bytecode_offset_ = kFunctionEntryBytecodeOffset;
 }
 
 void BytecodeOffsetIterator::UpdatePointers() {

src/baseline/bytecode-offset-iterator.h

@@ -31,6 +31,7 @@ class V8_EXPORT_PRIVATE BytecodeOffsetIterator {
     DCHECK(!done());
     current_pc_start_offset_ = current_pc_end_offset_;
     current_pc_end_offset_ += ReadPosition();
+    current_bytecode_offset_ = bytecode_iterator_.current_offset();
     bytecode_iterator_.Advance();
   }
 
@@ -38,20 +39,14 @@ class V8_EXPORT_PRIVATE BytecodeOffsetIterator {
     while (current_bytecode_offset() < bytecode_offset) {
       Advance();
     }
-    DCHECK(bytecode_offset == current_bytecode_offset() ||
-           // If kFunctionEntryBytecodeOffset is passed as bytecode_ofset, we
-           // want to return the PC for the first real bytecode.
-           bytecode_offset == kFunctionEntryBytecodeOffset);
+    DCHECK_EQ(bytecode_offset, current_bytecode_offset());
   }
 
   inline void AdvanceToPCOffset(Address pc_offset) {
     while (current_pc_end_offset() < pc_offset) {
       Advance();
     }
-    // pc could be inside the baseline prologue, wich means we didn't record any
-    // position for it.
-    DCHECK(pc_offset > current_pc_start_offset() ||
-           current_bytecode_offset() == 0);
+    DCHECK_GT(pc_offset, current_pc_start_offset());
     DCHECK_LE(pc_offset, current_pc_end_offset());
   }
 
@@ -68,7 +63,7 @@ class V8_EXPORT_PRIVATE BytecodeOffsetIterator {
   }
 
   inline int current_bytecode_offset() const {
-    return bytecode_iterator_.current_offset();
+    return current_bytecode_offset_;
   }
 
   static void UpdatePointersCallback(void* iterator) {
@@ -89,6 +84,7 @@ class V8_EXPORT_PRIVATE BytecodeOffsetIterator {
   int current_index_;
   Address current_pc_start_offset_;
   Address current_pc_end_offset_;
+  int current_bytecode_offset_;
   BytecodeArray bytecode_handle_storage_;
   interpreter::BytecodeArrayIterator bytecode_iterator_;
   LocalHeap* local_heap_;

src/d8/d8.cc

@@ -1851,6 +1851,11 @@ void Shell::TestVerifySourcePositions(
                i_isolate);
     offset_iterator = std::make_unique<i::baseline::BytecodeOffsetIterator>(
         bytecode_offsets, bytecodes);
+    // A freshly initiated BytecodeOffsetIterator points to the prologue.
+    DCHECK_EQ(offset_iterator->current_pc_start_offset(), 0);
+    DCHECK_EQ(offset_iterator->current_bytecode_offset(),
+              i::kFunctionEntryBytecodeOffset);
+    offset_iterator->Advance();
   }
   while (!bytecode_iterator.done()) {
     if (has_baseline) {