[ptr-compr] Remove explicit Compress/Decompress functions for CSA.

Code stub assembler does implicit compression / decompression when loading values from
the heap. As a result, we shouldn't expose explicit compress / decompress operators.

BUG=v8:7703

Change-Id: I72b7b862b48f19e918db0e283d1be065a2651b44
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1637879
Auto-Submit: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61955}

src/compiler/code-assembler.cc

@@ -1140,14 +1140,6 @@ Node* CodeAssembler::Retain(Node* value) {
   return raw_assembler()->Retain(value);
 }
 
-Node* CodeAssembler::ChangeTaggedToCompressed(Node* tagged) {
-  return raw_assembler()->ChangeTaggedToCompressed(tagged);
-}
-
-Node* CodeAssembler::ChangeCompressedToTagged(Node* compressed) {
-  return raw_assembler()->ChangeCompressedToTagged(compressed);
-}
-
 Node* CodeAssembler::Projection(int index, Node* value) {
   DCHECK_LT(index, value->op()->ValueOutputCount());
   return raw_assembler()->Projection(index, value);

src/compiler/code-assembler.h

@@ -1217,10 +1217,6 @@ class V8_EXPORT_PRIVATE CodeAssembler {
   // Projections
   Node* Projection(int index, Node* value);
 
-  // Pointer compression and decompression.
-  Node* ChangeTaggedToCompressed(Node* tagged);
-  Node* ChangeCompressedToTagged(Node* compressed);
-
   template <int index, class T1, class T2>
   TNode<typename std::tuple_element<index, std::tuple<T1, T2>>::type>
   Projection(TNode<PairT<T1, T2>> value) {