[ptr-compr] Avoid (de)compressions in CheckSmi

Avoids unnecessary compression and decompression nodes since we
are going to be able to check for smis without needing to decompress and
re-compress.

It was doing a CheckedInt32ToTaggedSigned ->
ChangeTaggedSignedToCompressedSigned combo, where we could just do
CheckedInt32ToCompressedSigned.

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: I0bbbbb5bd4744c49840c84b2fcb775fe6b603de0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1714878
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62917}

src/compiler/simplified-operator-reducer.cc

@@ -143,6 +143,33 @@ Reduction SimplifiedOperatorReducer::Reduce(Node* node) {
       }
       break;
     }
+    case IrOpcode::kChangeTaggedSignedToCompressedSigned: {
+      DCHECK(COMPRESS_POINTERS_BOOL);
+      NodeMatcher m(node->InputAt(0));
+      if (m.IsChangeInt31ToTaggedSigned()) {
+        Node* new_node = graph()->NewNode(
+            simplified()->ChangeInt31ToCompressedSigned(), m.InputAt(0));
+        return Replace(new_node);
+      } else if (m.IsCheckedInt32ToTaggedSigned()) {
+        // Create a new checked node that outputs CompressedSigned values, with
+        // an explicit decompression after it.
+        Node* new_checked = graph()->CloneNode(m.node());
+        NodeProperties::ChangeOp(
+            new_checked, simplified()->CheckedInt32ToCompressedSigned(
+                             CheckParametersOf(m.node()->op()).feedback()));
+        Node* new_decompression = graph()->NewNode(
+            machine()->ChangeCompressedSignedToTaggedSigned(), new_checked);
+
+        // For all uses of the old checked node, instead insert the new "checked
+        // + decompression". Also, update control and effect.
+        ReplaceWithValue(m.node(), new_decompression, new_checked, new_checked);
+
+        // In the current node, we can skip the decompression since we are going
+        // to have a Decompression + Compression combo.
+        return Replace(new_checked);
+      }
+      break;
+    }
     case IrOpcode::kCheckedTaggedToInt32:
     case IrOpcode::kCheckedTaggedSignedToInt32: {
       NodeMatcher m(node->InputAt(0));
@@ -267,6 +294,10 @@ MachineOperatorBuilder* SimplifiedOperatorReducer::machine() const {
   return jsgraph()->machine();
 }
 
+SimplifiedOperatorBuilder* SimplifiedOperatorReducer::simplified() const {
+  return jsgraph()->simplified();
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8