Implement UnaligedLoad and UnaligedStore turbofan operators.

src/compiler/wasm-compiler.cc

Index: src/compiler/wasm-compiler.cc
diff --git a/src/compiler/wasm-compiler.cc b/src/compiler/wasm-compiler.cc
index e7508c26ddffe32340289b2ed64342fb4d809590..8a6c5c61f2dcb573e87dbdba198ae7ad77699d8d 100644
--- a/src/compiler/wasm-compiler.cc
+++ b/src/compiler/wasm-compiler.cc
@@ -2895,7 +2895,13 @@ Node* WasmGraphBuilder::LoadMem(wasm::LocalType type, MachineType memtype,
                             MemBuffer(offset), index, *effect_, *control_);
     *effect_ = load;
   } else {
-    load = BuildUnalignedLoad(type, memtype, index, offset, alignment);
+    if (jsgraph()->machine()->UnalignedLoad(memtype).IsSupported()) {
+      load = graph()->NewNode(jsgraph()->machine()->UnalignedLoad(memtype).op(),
+                              MemBuffer(offset), index, *effect_, *control_);
+      *effect_ = load;
+    } else {
+      load = BuildUnalignedLoad(type, memtype, index, offset, alignment);

[titzer, 2016/07/11 08:40:00]

I thought this routine would go away. Is it the case that the only other
platform that doesn't support unaligned accesses is arm, and the instruction
selector/code generator must implement this?

Otherwise, we end up with the complexity of both solutions :(

[ivica.bogosavljevic, 2016/07/11 09:34:43]

Agreed. In that case we'll make UnalignedLoad/UnalignedStore mandatory operator,
but it will never be called for those architectures that support unaligned
access. And the BuildUnalignedLoad goes away.

+    }
   }
 #if defined(V8_TARGET_BIG_ENDIAN)
   // TODO(john.yan) Implement byte swap turbofan operator
@@ -3036,7 +3042,16 @@ Node* WasmGraphBuilder::StoreMem(MachineType memtype, Node* index,
                          index, val, *effect_, *control_);
     *effect_ = store;
   } else {
-    store = BuildUnalignedStore(memtype, index, offset, alignment, val);
+    UnalignedStoreRepresentation rep(memtype.representation());
+
+    if (jsgraph()->machine()->UnalignedStore(rep).IsSupported()) {
+      store =
+          graph()->NewNode(jsgraph()->machine()->UnalignedStore(rep).op(),
+                           MemBuffer(offset), index, val, *effect_, *control_);
+      *effect_ = store;
+    } else {
+      store = BuildUnalignedStore(memtype, index, offset, alignment, val);
+    }
   }
 
   return store;