[WASM SIMD] Implement horizontal add for float and integer types.

src/compiler/machine-operator.h

Index: src/compiler/machine-operator.h
diff --git a/src/compiler/machine-operator.h b/src/compiler/machine-operator.h
index bca8d85f07ab5f4db0c22373910ea949469eaaf7..0f846ac2329abeb8203a2e3009b494cd6a2847a1 100644
--- a/src/compiler/machine-operator.h
+++ b/src/compiler/machine-operator.h
@@ -444,6 +444,7 @@ class V8_EXPORT_PRIVATE MachineOperatorBuilder final
   const Operator* F32x4RecipApprox();
   const Operator* F32x4RecipSqrtApprox();
   const Operator* F32x4Add();
+  const Operator* F32x4AddHoriz();
   const Operator* F32x4Sub();
   const Operator* F32x4Mul();
   const Operator* F32x4Div();
@@ -464,6 +465,7 @@ class V8_EXPORT_PRIVATE MachineOperatorBuilder final
   const Operator* I32x4Shl(int32_t);
   const Operator* I32x4ShrS(int32_t);
   const Operator* I32x4Add();
+  const Operator* I32x4AddHoriz();
   const Operator* I32x4Sub();
   const Operator* I32x4Mul();
   const Operator* I32x4MinS();
@@ -493,6 +495,7 @@ class V8_EXPORT_PRIVATE MachineOperatorBuilder final
   const Operator* I16x8SConvertI32x4();
   const Operator* I16x8Add();
   const Operator* I16x8AddSaturateS();
+  const Operator* I16x8AddHoriz();
   const Operator* I16x8Sub();
   const Operator* I16x8SubSaturateS();
   const Operator* I16x8Mul();