MIPS: Fix int64->int32 lowering in wasm-to-interpeter entry on big-endian archs.

WASM interpreter requires that parameters are stored in big-endian natural
memory order (higher bits on lower addresses and lower bits on higher address).
On the other hand, WASM compiled code naturally stores data in memory in
little-endian order. This CL implements big-endian support for passing
double and int64 parameters to WASM interpreter.

TEST=cctest/test-wasm-interpreter-entry/TestArgumentPassing_int64,
     cctest/test-wasm-interpreter-entry/TestArgumentPassing_AllTypes

Review-Url: https://codereview.chromium.org/2721053002
Cr-Commit-Position: refs/heads/master@{#43568}

src/compiler/wasm-compiler.cc

@@ -2977,30 +2977,30 @@ void WasmGraphBuilder::BuildWasmInterpreterEntry(
     Node* param = Param(param_index++);
     bool is_i64_as_two_params =
         jsgraph()->machine()->Is32() && sig->GetParam(i) == wasm::kWasmI64;
-    MachineRepresentation param_rep =
-        is_i64_as_two_params ? wasm::kWasmI32 : sig->GetParam(i);
-    StoreRepresentation store_rep(param_rep, WriteBarrierKind::kNoWriteBarrier);
-    *effect_ =
-        graph()->NewNode(jsgraph()->machine()->Store(store_rep), arg_buffer,
-                         Int32Constant(offset), param, *effect_, *control_);
 
     if (is_i64_as_two_params) {
-      offset += 1 << ElementSizeLog2Of(wasm::kWasmI32);
-    } else {
-      offset += RoundUpToMultipleOfPowOf2(1 << ElementSizeLog2Of(param_rep), 8);
-    }
+      StoreRepresentation store_rep(wasm::kWasmI32,
+                                    WriteBarrierKind::kNoWriteBarrier);
+      *effect_ =
+          graph()->NewNode(jsgraph()->machine()->Store(store_rep), arg_buffer,
+                           Int32Constant(offset + kInt64LowerHalfMemoryOffset),
+                           param, *effect_, *control_);
 
-    // TODO(clemensh): Respect endianess here. Might need to swap upper and
-    // lower word.
-    if (is_i64_as_two_params) {
-      // Also store the upper half.
       param = Param(param_index++);
-      StoreRepresentation store_rep(wasm::kWasmI32,
+      *effect_ =
+          graph()->NewNode(jsgraph()->machine()->Store(store_rep), arg_buffer,
+                           Int32Constant(offset + kInt64UpperHalfMemoryOffset),
+                           param, *effect_, *control_);
+      offset += 8;
+
+    } else {
+      MachineRepresentation param_rep = sig->GetParam(i);
+      StoreRepresentation store_rep(param_rep,
                                     WriteBarrierKind::kNoWriteBarrier);
       *effect_ =
           graph()->NewNode(jsgraph()->machine()->Store(store_rep), arg_buffer,
                            Int32Constant(offset), param, *effect_, *control_);
-      offset += 1 << ElementSizeLog2Of(wasm::kWasmI32);
+      offset += RoundUpToMultipleOfPowOf2(1 << ElementSizeLog2Of(param_rep), 8);
     }
 
     DCHECK(IsAligned(offset, 8));

src/utils.h

@@ -520,6 +520,15 @@ const int kMinComplexMemCopy = 8;
 // ----------------------------------------------------------------------------
 // Miscellaneous
 
+// Memory offset for lower and higher bits in a 64 bit integer.
+#if defined(V8_TARGET_LITTLE_ENDIAN)
+static const int kInt64LowerHalfMemoryOffset = 0;
+static const int kInt64UpperHalfMemoryOffset = 4;
+#elif defined(V8_TARGET_BIG_ENDIAN)
+static const int kInt64LowerHalfMemoryOffset = 4;
+static const int kInt64UpperHalfMemoryOffset = 0;
+#endif  // V8_TARGET_LITTLE_ENDIAN
+
 // A static resource holds a static instance that can be reserved in
 // a local scope using an instance of Access.  Attempts to re-reserve
 // the instance will cause an error.