[ptr-compr] Specialize decompression with known Machine Representation

If we already know it has CompressedPointer representation, let's use
that information to decompress more efficiently.

Cq-Include-Trybots: luci.v8.try:v8_linux64_pointer_compression_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_linux64_arm64_pointer_compression_rel_ng
Bug: v8:7703
Change-Id: I3591bf67a7c0369c40ca6e7af16183530f8cd269
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1709049Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62887}

src/compiler/representation-change.cc

@@ -475,7 +475,7 @@ Node* RepresentationChanger::GetTaggedPointerRepresentationFor(
   } else if (output_rep == MachineRepresentation::kCompressedPointer) {
     if (use_info.type_check() == TypeCheckKind::kBigInt &&
         !output_type.Is(Type::BigInt())) {
-      node = InsertChangeCompressedToTagged(node);
+      node = InsertChangeCompressedPointerToTaggedPointer(node);
       op = simplified()->CheckBigInt(use_info.feedback());
     } else {
       op = machine()->ChangeCompressedPointerToTaggedPointer();
@@ -1741,6 +1741,12 @@ Node* RepresentationChanger::InsertTruncateInt64ToInt32(Node* node) {
   return jsgraph()->graph()->NewNode(machine()->TruncateInt64ToInt32(), node);
 }
 
+Node* RepresentationChanger::InsertChangeCompressedPointerToTaggedPointer(
+    Node* node) {
+  return jsgraph()->graph()->NewNode(machine()->ChangeCompressedToTagged(),
+                                     node);
+}
+
 Node* RepresentationChanger::InsertChangeCompressedToTagged(Node* node) {
   return jsgraph()->graph()->NewNode(machine()->ChangeCompressedToTagged(),
                                      node);

src/compiler/representation-change.h

@@ -395,6 +395,7 @@ class V8_EXPORT_PRIVATE RepresentationChanger final {
   Node* InsertChangeTaggedSignedToInt32(Node* node);
   Node* InsertChangeTaggedToFloat64(Node* node);
   Node* InsertChangeUint32ToFloat64(Node* node);
+  Node* InsertChangeCompressedPointerToTaggedPointer(Node* node);
   Node* InsertChangeCompressedToTagged(Node* node);
   Node* InsertConversion(Node* node, const Operator* op, Node* use_node);
   Node* InsertTruncateInt64ToInt32(Node* node);