From 4d62ca43001cc36e9994bfbc1c655e6b47c77c0d Mon Sep 17 00:00:00 2001
From: "mstarzinger@chromium.org"
 <mstarzinger@chromium.org@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Tue, 30 Apr 2013 08:21:52 +0000
Subject: [PATCH] Make UsePosition::hint immutable.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/14524008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14489 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/lithium-allocator.cc | 23 ++++++++++++-----------
 src/lithium-allocator.h  | 16 ++++++++--------
 2 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/src/lithium-allocator.cc b/src/lithium-allocator.cc
index 7bddef7f99..a010f4ea80 100644
--- a/src/lithium-allocator.cc
+++ b/src/lithium-allocator.cc
@@ -56,9 +56,11 @@ static inline LifetimePosition Max(LifetimePosition a, LifetimePosition b) {
 }
 
 
-UsePosition::UsePosition(LifetimePosition pos, LOperand* operand)
+UsePosition::UsePosition(LifetimePosition pos,
+                         LOperand* operand,
+                         LOperand* hint)
     : operand_(operand),
-      hint_(NULL),
+      hint_(hint),
       pos_(pos),
       next_(NULL),
       requires_reg_(false),
@@ -449,13 +451,14 @@ void LiveRange::AddUseInterval(LifetimePosition start,
 }
 
 
-UsePosition* LiveRange::AddUsePosition(LifetimePosition pos,
-                                       LOperand* operand,
-                                       Zone* zone) {
+void LiveRange::AddUsePosition(LifetimePosition pos,
+                               LOperand* operand,
+                               LOperand* hint,
+                               Zone* zone) {
   LAllocator::TraceAlloc("Add to live range %d use position %d\n",
                          id_,
                          pos.Value());
-  UsePosition* use_pos = new(zone) UsePosition(pos, operand);
+  UsePosition* use_pos = new(zone) UsePosition(pos, operand, hint);
   UsePosition* prev = NULL;
   UsePosition* current = first_pos_;
   while (current != NULL && current->pos().Value() < pos.Value()) {
@@ -470,8 +473,6 @@ UsePosition* LiveRange::AddUsePosition(LifetimePosition pos,
     use_pos->next_ = prev->next_;
     prev->next_ = use_pos;
   }
-
-  return use_pos;
 }
 
 
@@ -725,14 +726,14 @@ void LAllocator::Define(LifetimePosition position,
   if (range->IsEmpty() || range->Start().Value() > position.Value()) {
     // Can happen if there is a definition without use.
     range->AddUseInterval(position, position.NextInstruction(), zone_);
-    range->AddUsePosition(position.NextInstruction(), NULL, zone_);
+    range->AddUsePosition(position.NextInstruction(), NULL, NULL, zone_);
   } else {
     range->ShortenTo(position);
   }
 
   if (operand->IsUnallocated()) {
     LUnallocated* unalloc_operand = LUnallocated::cast(operand);
-    range->AddUsePosition(position, unalloc_operand, zone_)->set_hint(hint);
+    range->AddUsePosition(position, unalloc_operand, hint, zone_);
   }
 }
 
@@ -745,7 +746,7 @@ void LAllocator::Use(LifetimePosition block_start,
   if (range == NULL) return;
   if (operand->IsUnallocated()) {
     LUnallocated* unalloc_operand = LUnallocated::cast(operand);
-    range->AddUsePosition(position, unalloc_operand, zone_)->set_hint(hint);
+    range->AddUsePosition(position, unalloc_operand, hint, zone_);
   }
   range->AddUseInterval(block_start, position, zone_);
 }
diff --git a/src/lithium-allocator.h b/src/lithium-allocator.h
index 8b45531d9b..0cd5ae0e8e 100644
--- a/src/lithium-allocator.h
+++ b/src/lithium-allocator.h
@@ -244,13 +244,12 @@ class UseInterval: public ZoneObject {
 // Representation of a use position.
 class UsePosition: public ZoneObject {
  public:
-  UsePosition(LifetimePosition pos, LOperand* operand);
+  UsePosition(LifetimePosition pos, LOperand* operand, LOperand* hint);
 
   LOperand* operand() const { return operand_; }
   bool HasOperand() const { return operand_ != NULL; }
 
   LOperand* hint() const { return hint_; }
-  void set_hint(LOperand* hint) { hint_ = hint; }
   bool HasHint() const;
   bool RequiresRegister() const;
   bool RegisterIsBeneficial() const;
@@ -261,9 +260,9 @@ class UsePosition: public ZoneObject {
  private:
   void set_next(UsePosition* next) { next_ = next; }
 
-  LOperand* operand_;
-  LOperand* hint_;
-  LifetimePosition pos_;
+  LOperand* const operand_;
+  LOperand* const hint_;
+  LifetimePosition const pos_;
   UsePosition* next_;
   bool requires_reg_;
   bool register_beneficial_;
@@ -367,9 +366,10 @@ class LiveRange: public ZoneObject {
   void AddUseInterval(LifetimePosition start,
                       LifetimePosition end,
                       Zone* zone);
-  UsePosition* AddUsePosition(LifetimePosition pos,
-                              LOperand* operand,
-                              Zone* zone);
+  void AddUsePosition(LifetimePosition pos,
+                      LOperand* operand,
+                      LOperand* hint,
+                      Zone* zone);
 
   // Shorten the most recently added interval by setting a new start.
   void ShortenTo(LifetimePosition start);