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

src/machine-type.h

Index: src/machine-type.h
diff --git a/src/machine-type.h b/src/machine-type.h
index fd1d41dcc3a2dd3f8da800c02fd03bcf47c64d64..c61b40cbc381ca9d2837f5f1248161c3f845b0c1 100644
--- a/src/machine-type.h
+++ b/src/machine-type.h
@@ -29,8 +29,11 @@ enum class MachineRepresentation {
   kFloat32,
   kFloat64,
   kSimd128,
+  kSimdBool4,  // SIMD boolean vector types.
+  kSimdBool8,
+  kSimdBool16,
   kFirstFPRepresentation = kFloat32,
-  kLastRepresentation = kSimd128
+  kLastRepresentation = kSimdBool16
 };
 
 static_assert(static_cast<int>(MachineRepresentation::kLastRepresentation) <
@@ -127,6 +130,18 @@ class MachineType {
   static MachineType Simd128() {
     return MachineType(MachineRepresentation::kSimd128, MachineSemantic::kNone);
   }
+  static MachineType SimdBool4() {
+    return MachineType(MachineRepresentation::kSimdBool4,
+                       MachineSemantic::kNone);
+  }
+  static MachineType SimdBool8() {
+    return MachineType(MachineRepresentation::kSimdBool8,
+                       MachineSemantic::kNone);
+  }
+  static MachineType SimdBool16() {
+    return MachineType(MachineRepresentation::kSimdBool16,
+                       MachineSemantic::kNone);
+  }
   static MachineType Pointer() {
     return MachineType(PointerRepresentation(), MachineSemantic::kNone);
   }
@@ -173,6 +188,18 @@ class MachineType {
   static MachineType RepSimd128() {
     return MachineType(MachineRepresentation::kSimd128, MachineSemantic::kNone);
   }
+  static MachineType RepSimdBool4() {
+    return MachineType(MachineRepresentation::kSimdBool4,
+                       MachineSemantic::kNone);
+  }
+  static MachineType RepSimdBool8() {
+    return MachineType(MachineRepresentation::kSimdBool8,
+                       MachineSemantic::kNone);
+  }
+  static MachineType RepSimdBool16() {
+    return MachineType(MachineRepresentation::kSimdBool16,
+                       MachineSemantic::kNone);
+  }
   static MachineType RepTagged() {
     return MachineType(MachineRepresentation::kTagged, MachineSemantic::kNone);
   }
@@ -201,6 +228,12 @@ class MachineType {
         return MachineType::Float64();
       case MachineRepresentation::kSimd128:
         return MachineType::Simd128();
+      case MachineRepresentation::kSimdBool4:
+        return MachineType::SimdBool4();
+      case MachineRepresentation::kSimdBool8:
+        return MachineType::SimdBool8();
+      case MachineRepresentation::kSimdBool16:
+        return MachineType::SimdBool16();
       case MachineRepresentation::kTagged:
         return MachineType::AnyTagged();
       case MachineRepresentation::kTaggedSigned: