From e14463e07e4d4e19f2d26b6f6d5df79371e4d17c Mon Sep 17 00:00:00 2001
From: "bmeurer@chromium.org"
 <bmeurer@chromium.org@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Thu, 6 Feb 2014 12:35:17 +0000
Subject: [PATCH] Cosmetic cleanup for GVN.

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/153563006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19150 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/hydrogen-gvn.cc | 61 +++++++++++++++++++++++++++--------------------------
 src/hydrogen-gvn.h  | 11 +---------
 2 files changed, 32 insertions(+), 40 deletions(-)

diff --git a/src/hydrogen-gvn.cc b/src/hydrogen-gvn.cc
index 0628ff7..daca593 100644
--- a/src/hydrogen-gvn.cc
+++ b/src/hydrogen-gvn.cc
@@ -364,47 +364,48 @@ void HSideEffectMap::Store(GVNFlagSet flags, HInstruction* instr) {
 
 
 HGlobalValueNumberingPhase::HGlobalValueNumberingPhase(HGraph* graph)
-      : HPhase("H_Global value numbering", graph),
-        removed_side_effects_(false),
-        block_side_effects_(graph->blocks()->length(), zone()),
-        loop_side_effects_(graph->blocks()->length(), zone()),
-        visited_on_paths_(graph->blocks()->length(), zone()) {
-    ASSERT(!AllowHandleAllocation::IsAllowed());
-    block_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
-                                 zone());
-    loop_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
+    : HPhase("H_Global value numbering", graph),
+      removed_side_effects_(false),
+      block_side_effects_(graph->blocks()->length(), zone()),
+      loop_side_effects_(graph->blocks()->length(), zone()),
+      visited_on_paths_(graph->blocks()->length(), zone()) {
+  ASSERT(!AllowHandleAllocation::IsAllowed());
+  block_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
                                 zone());
+  loop_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
+                              zone());
 }
 
 
-void HGlobalValueNumberingPhase::Reset() {
-  ASSERT(block_side_effects_.length() == graph()->blocks()->length());
-  ASSERT(loop_side_effects_.length() == graph()->blocks()->length());
-  for (int i = 0; i < graph()->blocks()->length(); ++i) {
-    block_side_effects_[i] = GVNFlagSet();
-    loop_side_effects_[i] = GVNFlagSet();
-  }
-  visited_on_paths_.Clear();
-}
+void HGlobalValueNumberingPhase::Run() {
+  ASSERT(!removed_side_effects_);
+  for (int i = FLAG_gvn_iterations; i > 0; --i) {
+    // Compute the side effects.
+    ComputeBlockSideEffects();
+
+    // Perform loop invariant code motion if requested.
+    if (FLAG_loop_invariant_code_motion) LoopInvariantCodeMotion();
 
+    // Perform the actual value numbering.
+    AnalyzeGraph();
 
-void HGlobalValueNumberingPhase::Analyze() {
-  removed_side_effects_ = false;
-  ComputeBlockSideEffects();
-  if (FLAG_loop_invariant_code_motion) {
-    LoopInvariantCodeMotion();
+    // Continue GVN if we removed any side effects.
+    if (!removed_side_effects_) break;
+    removed_side_effects_ = false;
+
+    // Clear all side effects.
+    ASSERT_EQ(block_side_effects_.length(), graph()->blocks()->length());
+    ASSERT_EQ(loop_side_effects_.length(), graph()->blocks()->length());
+    for (int i = 0; i < graph()->blocks()->length(); ++i) {
+      block_side_effects_[i].RemoveAll();
+      loop_side_effects_[i].RemoveAll();
+    }
+    visited_on_paths_.Clear();
   }
-  AnalyzeGraph();
 }
 
 
 void HGlobalValueNumberingPhase::ComputeBlockSideEffects() {
-  // The Analyze phase of GVN can be called multiple times. Clear loop side
-  // effects before computing them to erase the contents from previous Analyze
-  // passes.
-  for (int i = 0; i < loop_side_effects_.length(); ++i) {
-    loop_side_effects_[i].RemoveAll();
-  }
   for (int i = graph()->blocks()->length() - 1; i >= 0; --i) {
     // Compute side effects for the block.
     HBasicBlock* block = graph()->blocks()->at(i);
diff --git a/src/hydrogen-gvn.h b/src/hydrogen-gvn.h
index 23b2440..4e4f349 100644
--- a/src/hydrogen-gvn.h
+++ b/src/hydrogen-gvn.h
@@ -41,18 +41,9 @@ class HGlobalValueNumberingPhase : public HPhase {
  public:
   explicit HGlobalValueNumberingPhase(HGraph* graph);
 
-  void Run() {
-    int max_fixpoint_iteration_count = FLAG_gvn_iterations;
-    for (int i = 0; i < max_fixpoint_iteration_count; i++) {
-      Analyze();
-      if (!removed_side_effects_) break;
-      Reset();
-    }
-  }
+  void Run();
 
  private:
-  void Reset();
-  void Analyze();
   GVNFlagSet CollectSideEffectsOnPathsToDominatedBlock(
       HBasicBlock* dominator,
       HBasicBlock* dominated);
-- 
2.7.4