ARM64: Avoid regeneration of constants.

src/arm64/lithium-arm64.h

Index: src/arm64/lithium-arm64.h
diff --git a/src/arm64/lithium-arm64.h b/src/arm64/lithium-arm64.h
index be053ddbbda026ab18a97d07433d04b43f8fbcc3..fc6e667c6061295788eea765721d57f7616cff96 100644
--- a/src/arm64/lithium-arm64.h
+++ b/src/arm64/lithium-arm64.h
@@ -3012,6 +3012,50 @@ class LWrapReceiver V8_FINAL : public LTemplateInstruction<1, 2, 0> {
 };
 
 
+class ConstantCache {
+ public:
+  ConstantCache() {}
+
+  class ConstantCacheLevel {
+   public:
+    void Cache(HConstant* constant) { cached_constants_.insert(constant); }
+    bool IsCached(HConstant* constant) {
+      return cached_constants_.find(constant) != cached_constants_.end();
+    }
+
+   private:
+    std::set<HConstant*> cached_constants_;
+  };
+
+  void Clear() { cache_levels_.clear(); }
+
+  void Cache(HConstant* constant, HBasicBlock* block) {
+    cache_levels_[block].Cache(constant);
+  }
+
+  bool IsCached(HConstant* constant, HBasicBlock* block) {
+    HBasicBlock* base_block = block;
+    std::map<HBasicBlock*, ConstantCacheLevel>::iterator it;
+    while (block != NULL) {
+      it = cache_levels_.find(block);
+      if (it != cache_levels_.end() && it->second.IsCached(constant)) {
+        if (base_block != block) {
+          // Avoid traversing the dominator blocks multiple times for the same
+          // constant.
+          cache_levels_[block].Cache(constant);
+        }
+        return true;
+      }
+      block = block->dominator();
+    }
+    return false;
+  }
+
+ private:
+  std::map<HBasicBlock*, ConstantCacheLevel> cache_levels_;
+};
+
+
 class LChunkBuilder;
 class LPlatformChunk V8_FINAL : public LChunk {
  public:
@@ -3055,6 +3099,13 @@ class LChunkBuilder V8_FINAL : public LChunkBuilderBase {
 
   static bool HasMagicNumberForDivision(int32_t divisor);
 
+  bool IsCachedConstant(HConstant* constant, HBasicBlock* block) {
+    return constant_cache_.IsCached(constant, block);
+  }
+  void CacheConstant(HConstant* constant, HBasicBlock* block) {
+    constant_cache_.Cache(constant, block);
+  }
+
  private:
   enum Status {
     UNUSED,
@@ -3205,6 +3256,7 @@ class LChunkBuilder V8_FINAL : public LChunkBuilderBase {
   HInstruction* current_instruction_;
   HBasicBlock* current_block_;
   LAllocator* allocator_;
+  ConstantCache constant_cache_;
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };