[turbofan] Remove OSR special case in loop assignment analysis

Now that OSR is done during graph building, we no longer have to
special-case OSR loops in the loop assignment analysis, as we no longer
have the restriction that registers are 'assigned' an OSRValue inside
the loop.

Bug: v8:6518
Change-Id: Ib4fa139091d77efa16246ddc6e63a10cbb877ee4
Reviewed-on: https://chromium-review.googlesource.com/615167Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47367}

src/compiler/bytecode-analysis.cc

@@ -42,7 +42,6 @@ void BytecodeLoopAssignments::AddList(interpreter::Register r, uint32_t count) {
   }
 }
 
-void BytecodeLoopAssignments::AddAll() { bit_vector_->AddAll(); }
 
 void BytecodeLoopAssignments::Union(const BytecodeLoopAssignments& other) {
   bit_vector_->Union(*other.bit_vector_);
@@ -281,9 +280,6 @@ void BytecodeAnalysis::Analyze(BailoutId osr_bailout_id) {
 
       if (is_osr_loop) {
         osr_entry_point_ = loop_header;
-        // OSR "assigns" everything to OSR values on entry into an OSR loop, so
-        // we need to make sure to considered everything to be assigned.
-        loop_stack_.top().loop_info->assignments().AddAll();
       }
 
       // Save the index so that we can do another pass later.

src/compiler/bytecode-analysis.h

@@ -26,7 +26,6 @@ class V8_EXPORT_PRIVATE BytecodeLoopAssignments {
 
   void Add(interpreter::Register r);
   void AddList(interpreter::Register r, uint32_t count);
-  void AddAll();
   void Union(const BytecodeLoopAssignments& other);
 
   bool ContainsParameter(int index) const;