Fix portable-simd tests

Author: bjorn3

src/intrinsics/llvm_aarch64.rs

@@ -243,6 +243,20 @@ pub(crate) fn codegen_aarch64_llvm_intrinsic_call<'tcx>(
         }
 
         // FIXME generalize vector types
+        "llvm.aarch64.neon.tbl1.v8i8" => {
+            intrinsic_args!(fx, args => (t, idx); intrinsic);
+
+            let zero = fx.bcx.ins().iconst(types::I8, 0);
+            for i in 0..8 {
+                let idx_lane = idx.value_lane(fx, i).load_scalar(fx);
+                let is_zero =
+                    fx.bcx.ins().icmp_imm(IntCC::UnsignedGreaterThanOrEqual, idx_lane, 16);
+                let t_idx = fx.bcx.ins().uextend(fx.pointer_type, idx_lane);
+                let t_lane = t.value_lane_dyn(fx, t_idx).load_scalar(fx);
+                let res = fx.bcx.ins().select(is_zero, zero, t_lane);
+                ret.place_lane(fx, i).to_ptr().store(fx, res, MemFlags::trusted());
+            }
+        }
         "llvm.aarch64.neon.tbl1.v16i8" => {
             intrinsic_args!(fx, args => (t, idx); intrinsic);