[Mono] Support get_Count and get_AllBitsSet for mini JIT on Arm64 (#84180)

* Support get_Count and get_AllBitsSet

* nint and nuint are 8 bytes on arm64 as well.

* Fix syntax

src/mono/mono/mini/cpu-arm64.mdesc

@@ -497,6 +497,7 @@ atomic_store_r4: dest:b src1:f len:28
 atomic_store_r8: dest:b src1:f len:24
 xbinop: dest:x src1:x src2:x len:8 clob:1
 xzero: dest:x len:4
+xones: dest:x len:8
 xmove: dest:x src1:x len:4
 xconst: dest:x len:10
 xcompare: dest:x src1:x src2:x len:4

src/mono/mono/mini/mini-arm64.c

@@ -3910,6 +3910,10 @@ mono_arch_output_basic_block (MonoCompile *cfg, MonoBasicBlock *bb)
 		case OP_XZERO:
 			arm_neon_eor_16b (code, dreg, dreg, dreg);
 			break;
+		case OP_XONES:
+			arm_neon_eor_16b (code, dreg, dreg, dreg);
+			arm_neon_not_16b (code, dreg, dreg);
+			break;
 		case OP_XEXTRACT: 
 			code = emit_xextract (code, VREG_FULL, ins->inst_c0, dreg, sreg1);
 			break;

src/mono/mono/mini/simd-intrinsics.c

@@ -387,7 +387,7 @@ emit_simd_ins_for_binary_op (MonoCompile *cfg, MonoClass *klass, MonoMethodSigna
 			case SN_Multiply:
 			case SN_op_Multiply: {
 #ifdef TARGET_ARM64
-				if (!COMPILE_LLVM (cfg) && (arg_type == MONO_TYPE_I8 || arg_type == MONO_TYPE_U8))
+				if (!COMPILE_LLVM (cfg) && (arg_type == MONO_TYPE_I8 || arg_type == MONO_TYPE_U8 || arg_type == MONO_TYPE_I || arg_type == MONO_TYPE_U))
 					return NULL;
 #endif
 				if (fsig->params [1]->type != MONO_TYPE_GENERICINST) 
@@ -1950,32 +1950,10 @@ emit_vector64_vector128_t (MonoCompile *cfg, MonoMethod *cmethod, MonoMethodSign
 		return NULL;
 #endif
 
-// FIXME: This limitation could be removed once everything here are supported by mini JIT on arm64
+// FIXME: Support Vector64 for mini JIT on arm64
 #ifdef TARGET_ARM64
-	if (!COMPILE_LLVM (cfg)) {
+	if (!COMPILE_LLVM (cfg) && (size != 16))
 		return NULL;
-		if (size != 16)
-			return NULL;
-		switch (id) {
-		case SN_get_One:
-		case SN_get_Zero:
-		case SN_op_OnesComplement:
-		case SN_op_UnaryNegation:
-		case SN_op_UnaryPlus:
-		case SN_op_Addition:
-		case SN_op_Subtraction:
-		case SN_op_BitwiseAnd:
-		case SN_op_BitwiseOr:
-		case SN_op_ExclusiveOr:
-		case SN_op_Equality:
-		case SN_op_Inequality:
-		case SN_op_Division:
-		case SN_op_Multiply:
-			break;
-		default:
-			return NULL;
-		}
-	}
 #endif
 
 	switch (id) {