[V8] Implement SIMD Boolean vector types to allow mask registers.

src/compiler/register-allocator.cc

Index: src/compiler/register-allocator.cc
diff --git a/src/compiler/register-allocator.cc b/src/compiler/register-allocator.cc
index c758b1e5b77b189fba2f806521682548a2c668b0..eb8d03eed529aa061f835c2ad674e738b118e803 100644
--- a/src/compiler/register-allocator.cc
+++ b/src/compiler/register-allocator.cc
@@ -86,6 +86,10 @@ int GetByteWidth(MachineRepresentation rep) {
       return kDoubleSize;
     case MachineRepresentation::kSimd128:
       return kSimd128Size;
+    case MachineRepresentation::kSimdBool4:
+    case MachineRepresentation::kSimdBool8:
+    case MachineRepresentation::kSimdBool16:
+      return kSimdMaskRegisters ? kPointerSize : kSimd128Size;
     case MachineRepresentation::kNone:
       break;
   }