Extend bounds check elimination to constant keys.

src/hydrogen-bce.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/hydrogen-bce.h"
 
 namespace v8 {
 namespace internal {
 
 
@@ skipping 36 matching lines @@
     } else if (check->index()->IsSub()) {
       HSub* index = HSub::cast(check->index());
       is_sub = true;
       if (index->left()->IsConstant()) {
         constant = HConstant::cast(index->left());
         index_base = index->right();
       } else if (index->right()->IsConstant()) {
         constant = HConstant::cast(index->right());
         index_base = index->left();
       }
+    } else if (check->index()->IsConstant()) {
+      index_base = check->block()->graph()->GetConstant0();
+      constant = HConstant::cast(check->index());
     }
 
     if (constant != NULL && constant->HasInteger32Value()) {
       *offset = is_sub ? - constant->Integer32Value()
                        : constant->Integer32Value();
     } else {
       *offset = 0;
       index_base = check->index();
     }
 
@@ skipping 148 matching lines @@
   int32_t upper_offset_;
   HBasicBlock* basic_block_;
   HBoundsCheck* lower_check_;
   HBoundsCheck* upper_check_;
   BoundsCheckBbData* next_in_bb_;
   BoundsCheckBbData* father_in_dt_;
 
   void MoveIndexIfNecessary(HValue* index_raw,
                             HBoundsCheck* insert_before,
                             HInstruction* end_of_scan_range) {
-    if (!index_raw->IsAdd() && !index_raw->IsSub()) {
-      // index_raw can be HAdd(index_base, offset), HSub(index_base, offset),
-      // or index_base directly. In the latter case, no need to move anything.
-      return;
-    }
-    HArithmeticBinaryOperation* index =
-        HArithmeticBinaryOperation::cast(index_raw);
-    HValue* left_input = index->left();
-    HValue* right_input = index->right();
-    bool must_move_index = false;
-    bool must_move_left_input = false;
-    bool must_move_right_input = false;
-    for (HInstruction* cursor = end_of_scan_range; cursor != insert_before;) {
-      if (cursor == left_input) must_move_left_input = true;
-      if (cursor == right_input) must_move_right_input = true;
-      if (cursor == index) must_move_index = true;
-      if (cursor->previous() == NULL) {
-        cursor = cursor->block()->dominator()->end();
-      } else {
-        cursor = cursor->previous();
+    // index_raw can be HAdd(index_base, offset), HSub(index_base, offset),
+    // HConstant(offset) or index_base directly.
+    // In the latter case, no need to move anything.
+    if (index_raw->IsAdd() || index_raw->IsSub()) {
+      HArithmeticBinaryOperation* index =
+          HArithmeticBinaryOperation::cast(index_raw);
+      HValue* left_input = index->left();
+      HValue* right_input = index->right();
+      bool must_move_index = false;
+      bool must_move_left_input = false;
+      bool must_move_right_input = false;
+      for (HInstruction* cursor = end_of_scan_range; cursor != insert_before;) {
+        if (cursor == left_input) must_move_left_input = true;
+        if (cursor == right_input) must_move_right_input = true;
+        if (cursor == index) must_move_index = true;
+        if (cursor->previous() == NULL) {
+          cursor = cursor->block()->dominator()->end();
+        } else {
+          cursor = cursor->previous();
+        }
       }
-    }
-    if (must_move_index) {
-      index->Unlink();
-      index->InsertBefore(insert_before);
-    }
-    // The BCE algorithm only selects mergeable bounds checks that share
-    // the same "index_base", so we'll only ever have to move constants.
-    if (must_move_left_input) {
-      HConstant::cast(left_input)->Unlink();
-      HConstant::cast(left_input)->InsertBefore(index);
-    }
-    if (must_move_right_input) {
-      HConstant::cast(right_input)->Unlink();
-      HConstant::cast(right_input)->InsertBefore(index);
+      if (must_move_index) {
+        index->Unlink();
+        index->InsertBefore(insert_before);
+      }
+      // The BCE algorithm only selects mergeable bounds checks that share
+      // the same "index_base", so we'll only ever have to move constants.
+      if (must_move_left_input) {
+        HConstant::cast(left_input)->Unlink();
+        HConstant::cast(left_input)->InsertBefore(index);
+      }
+      if (must_move_right_input) {
+        HConstant::cast(right_input)->Unlink();
+        HConstant::cast(right_input)->InsertBefore(index);
+      }
+    } else if (index_raw->IsConstant()) {
+      HConstant* index = HConstant::cast(index_raw);
+      bool must_move = false;
+      for (HInstruction* cursor = end_of_scan_range; cursor != insert_before;) {
+        if (cursor == index) must_move = true;
+        if (cursor->previous() == NULL) {
+          cursor = cursor->block()->dominator()->end();
+        } else {
+          cursor = cursor->previous();
+        }
+      }
+      if (must_move) {
+        index->Unlink();
+        index->InsertBefore(insert_before);
+      }
     }
   }
 
   void TightenCheck(HBoundsCheck* original_check,
                     HBoundsCheck* tighter_check,
                     int32_t new_offset) {
     ASSERT(original_check->length() == tighter_check->length());
     MoveIndexIfNecessary(tighter_check->index(), original_check, tighter_check);
     original_check->ReplaceAllUsesWith(original_check->index());
     original_check->SetOperandAt(0, tighter_check->index());
@@ skipping 171 matching lines @@
     if (data->FatherInDominatorTree()) {
       table_.Insert(data->Key(), data->FatherInDominatorTree(), zone());
     } else {
       table_.Delete(data->Key());
     }
     data = data->NextInBasicBlock();
   }
 }
 
 } }  // namespace v8::internal