Turn the representation changes into a proper HPhase.

src/hydrogen-representation-changes.cc

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "hydrogen-representation-changes.h"
+
+namespace v8 {
+namespace internal {
+
+void HRepresentationChangesPhase::InsertRepresentationChangeForUse(
+    HValue* value, HValue* use_value, int use_index, Representation to) {
+  // Insert the representation change right before its use. For phi-uses we
+  // insert at the end of the corresponding predecessor.
+  HInstruction* next = NULL;
+  if (use_value->IsPhi()) {
+    next = use_value->block()->predecessors()->at(use_index)->end();
+  } else {
+    next = HInstruction::cast(use_value);
+  }
+  // For constants we try to make the representation change at compile
+  // time. When a representation change is not possible without loss of
+  // information we treat constants like normal instructions and insert the
+  // change instructions for them.
+  HInstruction* new_value = NULL;
+  bool is_truncating = use_value->CheckFlag(HValue::kTruncatingToInt32);
+  bool allow_undefined_as_nan =
+      use_value->CheckFlag(HValue::kAllowUndefinedAsNaN);
+  if (value->IsConstant()) {
+    HConstant* constant = HConstant::cast(value);
+    // Try to create a new copy of the constant with the new representation.
+    new_value = (is_truncating && to.IsInteger32())
+        ? constant->CopyToTruncatedInt32(graph()->zone())
+        : constant->CopyToRepresentation(to, graph()->zone());
+  }
+
+  if (new_value == NULL) {
+    new_value = new(graph()->zone()) HChange(value, to,
+                                             is_truncating,
+                                             allow_undefined_as_nan);
+  }
+
+  new_value->InsertBefore(next);
+  use_value->SetOperandAt(use_index, new_value);
+}
+
+
+void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
+    HValue* value) {
+  Representation r = value->representation();
+  if (r.IsNone()) return;
+  if (value->HasNoUses()) return;
+
+  for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
+    HValue* use_value = it.value();
+    int use_index = it.index();
+    Representation req = use_value->RequiredInputRepresentation(use_index);
+    if (req.IsNone() || req.Equals(r)) continue;
+    InsertRepresentationChangeForUse(value, use_value, use_index, req);
+  }
+  if (value->HasNoUses()) {
+    ASSERT(value->IsConstant());
+    value->DeleteAndReplaceWith(NULL);
+  }
+
+  // The only purpose of a HForceRepresentation is to represent the value
+  // after the (possible) HChange instruction.  We make it disappear.
+  if (value->IsForceRepresentation()) {
+    value->DeleteAndReplaceWith(HForceRepresentation::cast(value)->value());
+  }
+}
+
+
+void HRepresentationChangesPhase::Run() {
+  // Compute truncation flag for phis: Initially assume that all
+  // int32-phis allow truncation and iteratively remove the ones that
+  // are used in an operation that does not allow a truncating
+  // conversion.
+  ZoneList<HPhi*> worklist(8, zone());
+
+  const ZoneList<HPhi*>* phi_list(graph()->phi_list());
+  for (int i = 0; i < phi_list->length(); i++) {
+    HPhi* phi = phi_list->at(i);
+    if (phi->representation().IsInteger32()) {
+      phi->SetFlag(HValue::kTruncatingToInt32);
+    }
+  }
+
+  for (int i = 0; i < phi_list->length(); i++) {
+    HPhi* phi = phi_list->at(i);
+    for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
+      // If a Phi is used as a non-truncating int32 or as a double,
+      // clear its "truncating" flag.
+      HValue* use = it.value();
+      Representation input_representation =
+          use->RequiredInputRepresentation(it.index());
+      if (!input_representation.IsInteger32() ||
+          !use->CheckFlag(HValue::kTruncatingToInt32)) {
+        if (FLAG_trace_representation) {
+          PrintF("#%d Phi is not truncating because of #%d %s\n",
+                 phi->id(), it.value()->id(), it.value()->Mnemonic());
+        }
+        phi->ClearFlag(HValue::kTruncatingToInt32);
+        worklist.Add(phi, zone());
+        break;
+      }
+    }
+  }
+
+  while (!worklist.is_empty()) {
+    HPhi* current = worklist.RemoveLast();
+    for (int i = 0; i < current->OperandCount(); ++i) {
+      HValue* input = current->OperandAt(i);
+      if (input->IsPhi() &&
+          input->representation().IsInteger32() &&
+          input->CheckFlag(HValue::kTruncatingToInt32)) {
+        if (FLAG_trace_representation) {
+          PrintF("#%d Phi is not truncating because of #%d %s\n",
+                 input->id(), current->id(), current->Mnemonic());
+        }
+        input->ClearFlag(HValue::kTruncatingToInt32);
+        worklist.Add(HPhi::cast(input), zone());
+      }
+    }
+  }
+
+  const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
+  for (int i = 0; i < blocks->length(); ++i) {
+    // Process phi instructions first.
+    const HBasicBlock* block(blocks->at(i));
+    const ZoneList<HPhi*>* phis = block->phis();
+    for (int j = 0; j < phis->length(); j++) {
+      InsertRepresentationChangesForValue(phis->at(j));
+    }
+
+    // Process normal instructions.
+    for (HInstruction* current = block->first(); current != NULL; ) {
+      HInstruction* next = current->next();
+      InsertRepresentationChangesForValue(current);
+      current = next;
+    }
+  }
+}
+
+} }  // namespace v8::internal