Implement UnalignedLoad and UnalignedStore in WASM using LoadByte/Shift/Or and StoreByte/Shift/And.

src/compiler/mips64/instruction-selector-mips64.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 2033 matching lines @@
          MachineOperatorBuilder::kFloat64RoundDown |
          MachineOperatorBuilder::kFloat32RoundDown |
          MachineOperatorBuilder::kFloat64RoundUp |
          MachineOperatorBuilder::kFloat32RoundUp |
          MachineOperatorBuilder::kFloat64RoundTruncate |
          MachineOperatorBuilder::kFloat32RoundTruncate |
          MachineOperatorBuilder::kFloat64RoundTiesEven |
          MachineOperatorBuilder::kFloat32RoundTiesEven;
 }
 
+// static
+MachineOperatorBuilder::UnalignedAccessConfig
+InstructionSelector::UnalignedAccessConfiguration() {
+  if (kArchVariant == kMips64r6) {
+    return MachineOperatorBuilder::UnalignedAccessConfig::
+        FullUnalignedAccessSupport();
+  } else {
+    DCHECK(kArchVariant == kMips64r2);
+    return MachineOperatorBuilder::UnalignedAccessConfig::
+        NoUnalignedAccessSupport();
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8