[ptr-compr] Add Smi tag test case to DecompressionOptimizer

Bug: v8:7703
Change-Id: I06c47aa4057362d52e53b6a45d4e8a5febb92c82
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1876055
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64643}

src/compiler/decompression-optimizer.cc

@@ -55,14 +55,16 @@ void DecompressionOptimizer::MarkNodes() {
 void DecompressionOptimizer::MarkNodeInputs(Node* node) {
   // Mark the value inputs.
   switch (node->opcode()) {
-    // TODO(v8:7703): To be removed when the TaggedEqual implementation stops
-    // using ChangeTaggedToCompressed.
+    // UNOPS.
+    // TODO(v8:7703): ChangeTaggedToCompressed case to be removed when the
+    // TaggedEqual implementation stops using ChangeTaggedToCompressed.
     case IrOpcode::kChangeTaggedToCompressed:
     case IrOpcode::kTruncateInt64ToInt32:
       DCHECK_EQ(node->op()->ValueInputCount(), 1);
       MaybeMarkAndQueueForRevisit(node->InputAt(0),
                                   State::kOnly32BitsObserved);  // value
       break;
+    // BINOPS.
     case IrOpcode::kWord32And:
     case IrOpcode::kWord32Equal:
       DCHECK_EQ(node->op()->ValueInputCount(), 2);
@@ -71,6 +73,7 @@ void DecompressionOptimizer::MarkNodeInputs(Node* node) {
       MaybeMarkAndQueueForRevisit(node->InputAt(1),
                                   State::kOnly32BitsObserved);  // value_1
       break;
+    // SPECIAL CASES.
     case IrOpcode::kStore:
     case IrOpcode::kProtectedStore:
     case IrOpcode::kUnalignedStore:

test/unittests/compiler/decompression-optimizer-unittest.cc

@@ -204,6 +204,34 @@ TEST_F(DecompressionOptimizerTest, Word32AndSmiCheck) {
   }
 }
 
+TEST_F(DecompressionOptimizerTest, Word32ShlSmiTag) {
+  // Skip test if decompression elimination is enabled.
+  if (FLAG_turbo_decompression_elimination) {
+    return;
+  }
+
+  // Define variables.
+  Node* const control = graph()->start();
+  Node* object = Parameter(Type::Any(), 0);
+  Node* effect = graph()->start();
+  Node* index = Parameter(Type::UnsignedSmall(), 1);
+
+  // Test only for AnyTagged, since TaggedPointer can't be Smi tagged.
+  // Create the graph.
+  Node* load = graph()->NewNode(machine()->Load(MachineType::AnyTagged()),
+                                object, index, effect, control);
+  Node* truncation = graph()->NewNode(machine()->TruncateInt64ToInt32(), load);
+  Node* smi_shift_bits =
+      graph()->NewNode(common()->Int32Constant(kSmiShiftSize + kSmiTagSize));
+  Node* word32_shl =
+      graph()->NewNode(machine()->Word32Shl(), truncation, smi_shift_bits);
+  graph()->SetEnd(
+      graph()->NewNode(machine()->ChangeInt32ToInt64(), word32_shl));
+  // Change the nodes, and test the change.
+  Reduce();
+  EXPECT_EQ(LoadMachRep(load), CompressedMachRep(MachineType::AnyTagged()));
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8