Vectorize codegen for left shift operator on byte vector

src/coreclr/jit/gentree.cpp

@@ -21017,6 +21017,20 @@ GenTree* Compiler::gtNewSimdBinOpNode(
 
             return gtNewSimdBinOpNode(GT_AND, type, shiftOp, maskOp, simdBaseJitType, simdSize);
         }
+
+        case GT_LSH:
+        {
+            assert(varTypeIsByte(simdBaseType));
+            GenTree* andShiftVal = fgMakeMultiUse(&op2ForLookup);
+            GenTree* shiftOp =
+                gtNewSimdBinOpNode(GT_LSH, type, op1, op2ForLookup,
+                                   varTypeIsUnsigned(simdBaseType) ? CORINFO_TYPE_USHORT : CORINFO_TYPE_SHORT,
+                                   simdSize);
+            GenTree* maskElement =
+                gtNewOperNode(GT_LSH, andShiftVal->TypeGet(), gtNewIconNode(0xFF), fgMakeMultiUse(&andShiftVal));
+            GenTree* mask = gtNewSimdCreateBroadcastNode(type, maskElement, simdBaseJitType, simdSize);
+            return gtNewSimdBinOpNode(GT_AND, type, shiftOp, mask, simdBaseJitType, simdSize);
+        }
 #endif // TARGET_XARCH
 
         case GT_MUL:

src/coreclr/jit/hwintrinsicxarch.cpp

@@ -3377,12 +3377,6 @@ GenTree* Compiler::impSpecialIntrinsic(NamedIntrinsic        intrinsic,
         {
             assert(sig->numArgs == 2);
 
-            if (varTypeIsByte(simdBaseType))
-            {
-                // byte and sbyte would require more work to support
-                break;
-            }
-
             if ((simdSize != 32) || compOpportunisticallyDependsOn(InstructionSet_AVX2))
             {
                 op2 = impPopStack().val;