[stubs] Fix Allocate macro in the CodeStubAssembler.

The macro was Using SmiTag(Int32Constant()) was causing some unnecessary shifts to be emitted in the deferred code.

Also, when allocating in new space, the macro now uses Runtime::kAllocateInNewSpace.

Review-Url: https://codereview.chromium.org/1945263002
Cr-Commit-Position: refs/heads/master@{#36023}

src/code-stub-assembler.cc

@@ -330,14 +330,19 @@ Node* CodeStubAssembler::AllocateRawUnaligned(Node* size_in_bytes,
 
   Bind(&runtime_call);
   // AllocateInTargetSpace does not use the context.
-  Node* context = IntPtrConstant(0);
-  Node* runtime_flags = SmiTag(Int32Constant(
-      AllocateDoubleAlignFlag::encode(false) |
-      AllocateTargetSpace::encode(flags & kPretenured
-                                      ? AllocationSpace::OLD_SPACE
-                                      : AllocationSpace::NEW_SPACE)));
-  Node* runtime_result = CallRuntime(Runtime::kAllocateInTargetSpace, context,
-                                     SmiTag(size_in_bytes), runtime_flags);
+  Node* context = SmiConstant(Smi::FromInt(0));
+
+  Node* runtime_result;
+  if (flags & kPretenured) {
+    Node* runtime_flags = SmiConstant(
+        Smi::FromInt(AllocateDoubleAlignFlag::encode(false) |
+                     AllocateTargetSpace::encode(AllocationSpace::OLD_SPACE)));
+    runtime_result = CallRuntime(Runtime::kAllocateInTargetSpace, context,
+                                 SmiTag(size_in_bytes), runtime_flags);
+  } else {
+    runtime_result = CallRuntime(Runtime::kAllocateInNewSpace, context,
+                                 SmiTag(size_in_bytes));
+  }
   result.Bind(runtime_result);
   Goto(&merge_runtime);